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Time to Rebuild? Part I
 
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Pelican Technical Article:

Time to Rebuild? Part I

Applicable Models:

Porsche 911 (1965-89)
Porsche 912 (1965-69)
Porsche 930 Turbo (1976-89)
When to Rebuild?

Indeed, this is a very common question, and one that is often not easily answered. Obviously, if there is the end of a rod sticking out of your engine case, then chances are, it’s time for a rebuild. However, with more subtle noises, broken pieces, and poor performance, the rebuild decision may not be crystal clear. In this section, I will provide you with some questions to ask yourself and some answers to common myths, in the attempt to correctly determine whether your engine needs to be rebuilt.

As with any serious medical condition, it’s always a wise idea to get a second opinion. The same is true with 911 engine rebuilds. Very often, I have heard of unscrupulous (or even over-meticulous) Porsche mechanics who have recommended, or even insisted on a rebuild, when not all of the signs pointed in that direction. Keep in mind that no matter how well-intentioned your mechanic may be, he may have a vested financial interest in seeing you rebuild your engine. Of course, not knowing that you’re armed with this book and prepared to do it yourself, he might recommend a full rebuild. Rebuilding engines is a good business, and will guarantee about 40 hours of labor for complete job.

My recommendation is that you take your car to a second, independent mechanic, and pay to have the car evaluated. Have him perform a leak-down test on the engine (see later in this chapter), and let him know up-front that you have a master mechanic friend waiting in the wings to rebuild the engine for you. The goal is to try to get an independent, unbiased expert view of the condition of your engine. Many of the problems with 911 engines can be somewhat subtle, and difficult for a novice to detect and decipher. I’ll give you some hints, tips, procedures, and clues to help you in the following sections, but getting at least two expert opinions is always a wise idea.

High Mileage Engines

Each derivative of the 911 has its own quirks and problems. Some of the engines are known for their longevity, and some are decidedly not. Just because your 911 engine has a lot of miles on it, doesn't mean that it's automatically time for a rebuild. With proper care and maintenance, certain 911 engines can easily last 250,000 miles or more. Of course, some years have had better track records than others, but the basic rules apply: if the engine was well cared for, and not abused, then it should last a long time, and gradually wear out. In general, the rule of thumb is that high-mileage is not a good yardstick measurement of engine condition. The methods by which the car was operated and maintained during its life affect the condition of the engine much more than the mileage total.

High mileage engines often show signs of their age in compression and leak-down tests, described later in this section. As the engines age and mileage increase, the small tolerances within the engine slowly become larger. While this usually doesn’t result in a catastrophic breakdown, high-mileage engines will gradually see their performance degrade as the mileage increases. Such an engine may be referred to as 'tired'.

Stock engines almost always last longer than modified engines. Higher compression ratios, aftermarket turbos, or superchargers will almost always place added stress on engines and make them wear out or fail quicker. Engines driven constantly on the track may especially show signs of wear. Race engines have such a typically short lifespan that their usage is usually tallied in hours run, rather than miles traveled.

Stock Engine Reliability

The 1978-89 engines are probably best known for having the longest life. It’s not uncommon to find a good, well-maintained 3.0L engine running strong with more than 200,000 miles on the clock. Then again, I have seen poorly maintained 3.0L engines with many broken head studs and barely over 100,000 miles on the odometer. It’s really a combination of maintenance and the luck-of-the-draw as to whether your 1978-89 engine will be one of the good ones that last or not. Just give you a reality-check, in the late-seventies and early 80’s, there were very few cars that lasted significantly past 100,000 miles, so the Porsche 911 engine was indeed way ahead of its time. The 911 Turbo engines also fit into this reliable category, despite the added stress placed on them.

The 1974-77 engines are decidedly the most unreliable of the bunch. That’s not to say that they are a bad engine. They have major design flaws that need to be fixed and repaired in order to become reliable and long-lasting. A properly repaired and maintained 2.7L should be able to last as long as it’s 1978-89 brethren. However, it’s very rare to find a stock 2.7L engine over 100,000 miles that has not been rebuilt. The 2.7L engines suffered from a host of problems: pulled head studs, worn valve guides, weak cases, and overheating problems caused by thermal reactors used on the exhaust system.

The 1969-73 engines were generally more reliable than the 2.7L engines. Despite using the weaker magnesium case, these engines didn’t stress the limits of the case, and were generally long-lived. 911T engines in particular, with their lower compression heads, seem to just run forever. The higher-compression ‘S’ models tend to wear out a little faster, but they are still probably good for 110,000 miles or so. One of the bigger weaknesses of these engines were the Biral cylinders, which don’t last nearly as long as the later-style Nikasil ones. Again, the longevity of these engines during this era was unprecedented, and helped Porsche earn its reputation for excellent engineering. In addition, with today’s modern motor oils, the life expectancy of these early engines is actually increasing.

Failed Smog Tests

Out here in sunny California, we have one of the most strictest emissions tests in the world. Cars are held up to high standards that seem to get higher each year. Recently the California Air Resource Board (CARB) instituted a dynometer test where the wheels of the car are placed on a roller, and tested for emissions at a specific speed. In addition, the tests monitor hydrocarbons, carbon monoxide, and nitrogen oxides (NOx). These tests are designed to monitor the emissions for engine conditions that might produce smog. Unfortunately, as the tests get tougher and tougher to pass, more 911 engines tend to fail. In some cases, the tests hold the cars to emissions standards that they were never designed to meet.
Just because your car fails the smog test, doesn’t necessarily mean that its engine needs to be rebuilt. In fact, a recently rebuilt engine will most certainly fail the test if it hasn’t been fully run-in yet. The best thing that you can do to get your car to pass a smog test is to make sure that it is running perfectly. Most of the time a non-passing car simply has its timing set incorrectly, or has a fuel injection problem. You must make sure that all of your fuel injection and ignition components are working 100% properly before you can assume that the engine mechanicals may be suspect. A compression or leak-down test should be able to let you know if your failure to pass smog is caused by internal engine wear.

Poor Performance and Poor Gas Mileage

When rings and valve guides begin to wear, the result is an increase in burnt oil inside the engine. Also seen is a decrease in compression. Both will have a negative impact on the power generated by your engine. The burnt oil is a contaminant in the combustion chamber and will interfere with the combustion process. The loss of compression will reduce your compression ratio, and limit the power output of the engine. Both will result in poor performance and poor fuel economy.

However, there are plenty of other factors that can affect fuel economy and power. Most notably, the fuel injection system needs to be maintained in top shape in order to achieve the most power out of your system. Make sure that you have eliminated both the fuel system and ignition system as a potential source of problems before you decide you need a rebuild. Also try to isolate and fix other obscure problems that you might not think of. Improper suspension alignment can seriously reduce power, as can improper tire inflations. Brake problems (especially with the emergency hand brake) can drag on the wheels and create some pretty significant drag. The other book in this series, “101 Projects for Your Porsche 911” has more information on fixing these problems.

Strange Engine Noises

Air-cooled engines are designed to expand and contract as they heat and cool. As such, it is very difficult to diagnose strange engine noises that occur when the engine is cold. It is not uncommon for the engine to make some unusual tapping or knocking noises when started stone cold. It’s the strange noises that are made when the engine is warm and running that are the ones to watch out for. All engine also tend to get noisier as they age, and clearances between parts inside the engine become larger.

Engine noises are indeed difficult to hear at times. What may be a loud noise from one area of the engine, may in fact be inaudible from another angle. Sometimes sitting inside the car, you will hear more of the lower-pitched noises, as the higher-pitched ones are filtered out by the cars’s insulation. Closing your eyes when listening to the engine helps to eliminate potential distractions, and allows you to concentrate on isolating the engine noises from one another. An automotive stethoscope is a useful tool for listening closely to the engine. This tool works best when placed against a solid piece of the engine. Local sounds from troubled components can be heard better through the stethoscope because it helps to isolate outside noise. A long wooden dowel is a good alternative to the stethoscope, but be careful not to stick it in your ear, as intermittent engine vibrations can sometimes knock it into the inside of your ear. A piece of rubber vacuum hose will work as well.

There are four basic types of noises that can come from the 911 engine. Intermittent noises occur at irregular intervals and seem to have no reasonable pattern to them. An example would be something rattling around inside one of the valve covers. There are noises that emanate with the crankshaft speed, and occur once every revolution. Then there are valve-train noises which come and go once every two revolutions (the valve train operates at half the speed of the crankshaft). Such a noise would include the rockers and valve noise. This is probably the most common noise heard on the 911 engine, and the fix may be to simply adjust the valves.

A common noise to hear is a loud squeaky noise from inside the engine while running. Such a noise can often be attributed to worn alternator bearings. Take the fan belt off, and run the engine for no more than 10-15 seconds and see if the noise disappears. If it does, you know the problem is with your fan, fan housing, or alternator.

Another common noise is piston slap. This is the sound that the piston makes on its power stroke when clearances between the piston and the cylinder are somewhat excessive. It’s a dull-thud clunk that can be heard every two rotations of the crankshaft. Piston slap is most commonly heard when the engine is warming up, before the piston to bore clearances have decreased due to the pistons expanding.

There are a whole host of noises associated with problems such as rod knock, noisy valves, broken rings, chain tensioner failure, detonation, and broken or pulled head studs. Unfortunately, I have discovered that it’s nearly impossible to accurately describe these noises in writing so that someone can diagnose them. The best suggestion would be to take your car to your mechanic and have him listen to the engine. The 911 engine can be a loud, noisy engine, and if you haven’t listened to a whole lot of them, your imagination can get the best of you. Of course, listening to other finely tuned 911 engines in cars owned by your friends will help you with an idea of what a normal 911 engine should be sounding like.

Oil Consumption & Smoking

As your engine ages, it will consume more oil. When the engine is brand new, all of the clearances inside the engine are easily filled with a thin film of oil. As the surfaces wear, the clearances enlarge, and oil begins to slip by them. This oil is then burned in the combustion chamber, as it seeps past the valve guides and piston rings. The wider the clearances, the more oil will be burned away. Also, some oils have different viscosities, and tend to burn at a higher rate than others. In general, thinner, lighter-weight oils have a tendency to flow more easily past worn parts in the engine. Use of a heavier weight oil in a tired engine may help to slightly reduce oil consumption.

In addition, excess clearances mean that the oil films that float the crankshaft bearings require more oil to work properly. Looser gap clearances between bearings means that oil flows more easily around the bearing journals. The result is that more oil is required to do the same task, and there is a corresponding drop in oil pressure and an increase in wear. This small drop in oil pressure can sometimes be seen if careful observance to oil pressure readings are taken over the life of the engine. In general, an increase in oil consumption, coupled with a decrease in oil pressure, is a sure-fire sign that the clearances in the engine have increased, and the engine needs to be rebuilt. In addition, the presence of oil in the combustion chamber may have an adverse affect on the combustion process. Oil tends to lower the effective octane rating of the fuel mixture, thus making the engine a bit more prone to harmful detonation.

So how much oil should your 911 engine be consuming? One quart per 1000 miles is about the standard amount for the 911 engine. Newly rebuilt engines with about 5,000 miles on them will usually burn this amount. If your engine is consuming significantly more oil than this, you have a problem. Consumption of two quarts per 1000 miles is certainly cause for concern.

There are two places that the oil can be lost, either past the piston rings, or the valve guides. If the car is excessively smoking, then there is significant oil being burned in the combustion chamber. Air-cooled engines expand significantly when they are run. It’s not uncommon for the entire engine to expand more than 1/8 of an inch side-to-side when heated from stone cold to operating temperature. This means that certain clearances that are designed to be optimum at operating temperature are sometimes not ideal when the engine is cold. Oil seepage when the engine is cold is considered normal. Just about every 911 engine smokes when it’s started, primarily because some oil has seeped into the combustion chamber when the engine was cold. This smoking is not necessarily a sign that the engine needs to be rebuilt. A more accurate test would be to check for significant smoke when the car is completely warmed up.

What smoke should you look for? White smoke is typically caused by condensation in the engine, and is generally harmless when seen on an air cooled engine. Black smoke means that there is a lot of unburned fuel in the combustion chamber that may be a sign that the car is running too rich. In general, blue, sooty smoke is burning oil. If your engine puts out a big puff of bluish smoke when pulling away from a stoplight, it’s probably a sign that the rings are significantly worn.

Worn rings also produce what is known as blow-by. Just as oil can enter into the combustion chamber, exhaust gases can also be blown into the crankcase when the piston fires. Such blow-by, as it is called, often comes out of the crankcase through the crankcase breather hose on the top front of the engine. This hose connects to the oil tank, and the exhaust gases are recirculated back into the engine through the filler neck on the oil tank. On other cars, blow-by is typically funneled back into the air filter through the positive crankcase ventilation valve (PCV).

Worn valve guides can also contribute to oil loss, although typically less than worn rings. In the mid-1970s, Porsche experimented with new types of valve guides that did not last long at all. As a result, many of the 1974-77 engines had to have their guides replaced at about 60,000 miles. Most of these engines have had this repair done, however, if you find that your engine has not, then you can expect that your guides will be well worn. Worn guides not only leak compression, but also can cause the heads of valves to overheat and break off. This is because close valve guide clearances are necessary for proper cooling of the valve. It should be noted that puffs of smoke on deceleration are usually a sign of worn guides and valve seals.

In addition to the oil burned naturally by the engine, your 911 engine can also lose a lot of oil due to leaks. Many 911 oil leaks drip onto the heat exchangers and are burned off by the high heat. As such, sometimes it's very difficult to gauge exactly how much oil is being burned by the engine, and how much is actually being lost to oil leaks.

Air-cooled engines are infamous for oil leaks. Whether it’s a Porsche 911 engine or a Volkswagen engine, air-cooled owners will fondly describe that burning oil smell that is characteristic of these cars. To be fair, the air-cooled cars must get their passenger compartment heat from heat exchangers that wrap around the exhaust pipes. If there is an oil leak onto these pipes, then the smell of burning oil will waft up into the passenger compartment. This is the reason why many air-cooled owners diligently try to chase down and repair oil leaks in their engines.

The 911 engine can leak oil from one of many different places. Fortunately, many of these oil leaks can be repaired without tearing down and rebuilding the engine. Project 21 from the book, “101 Projects for Your Porsche 911” details all of the common leaks that can be easily fixed without engine disassembly. If your main goal of rebuilding the engine is to fix some of these major oil leaks, I suggest that you read that section first.

There are a few major leaks that cannot be fixed without major engine work. Crankcase parting line leaks require disassembly, as do leaks between the heads and the cam towers. Leaks from between the chain housing and the cam towers also require major disassembly. Many times a leak will appear to be coming from one of these places when in fact it is leaking from a different point that is significantly easier to fix. Wash the underside of the car and track down all of the easy oil leaks before you decide that it’s time for a rebuild.

Head Stud Problems

One of the most common failures associated with the 911 engine is the breaking or pulling out of the cylinder head studs. These are long, shanked studs that are thinner in the middle than on the end sections were the threads are located. Shanked studs are typically designed in this manner to achieve a strong, coarse thread while keeping the center diameter of the stud at the optimum thickness – often designed with thermal considerations. When you remove your valve covers, you should do a quick inspection of your head studs. The head studs can be seen by looking deep down into the heads in the areas where the spark plugs are located. There are usually two problems associated with head studs – they either break off, or they pull out of the case and become loose. Both will result in the head stud barrel nuts falling off, and rattling around in the valve covers. Both are a bad sign for the engine.

The 1974-77 magnesium cases are most known for their pulled head studs. How does this happen? Magnesium is softer and lighter than aluminum. On the very early magnesium cases (1973 and earlier), the engine didn’t stress the limits of the magnesium case too much. With the advent of newer, and tougher emissions restrictions in the late 1970s, hotter running engines (hotter engines give off less emissions) began to stress the limits of the magnesium case. In addition, the increase of the displacement of the engine placed additional stresses on the engine cases. Particularly if the engine becomes overheated, it will expand and place additional stress on the threads of the studs that are inserted into the case. These stresses were exacerbated by the fact that the cylinder spigot was enlarged to accommodate the larger 2.7L cylinder. The enlarged bore removed crucial material in the area near where the cylinder head studs are mounted. The result is that the metal threads in the magnesium case yield, and begin to pull out. Once the engine cools down to it’s normal operating state, the stress subsides, but the studs remain pulled out of the magnesium case. The result is that the barrel nuts on the end of the studs become loose and fall off. Subsequent attempts to re-torque the nuts almost always results in further pulling of the stud. The appropriate torque for the heads can longer be maintained, and as a result, the heads become loose. This often creates a distinctive exhaust leak at the interface between the head and the cylinder. This phat-phat-phat sound is typical of a 2.7L engine with pulled head studs.

How can you tell if you have a pulled head stud? Simply pull off the valve covers (upper and lower), and check to see if you have any head stud barrel nuts floating around the inside the spark plug area. If you do, then chances are good that your magnesium case has pulled at least one stud. If the barrel nuts are still attached to the head studs, take a 10mm allen-head tool, and attempt to tighten them to factory specs (see Appendix X for the specification for your year engine). If the nuts simply spin and spin, then you probably have a pulled head stud. Don’t keep tightening it, as you can pull the stud so far out of the hole that it will be difficult to remove the nut later on when you disassemble the engine.

The repair involves a complete teardown of the engine, as you cannot easily and effectively repair the case without the use of a precision milling machine or drill press. The fix for pulled head studs is the installation of what are known as case-savers. These are threaded steel inserts that are installed into the case and reinforce the threads to be stronger than the bare metal threads within the case. The case-saver has a larger diameter than the original head stud, which results in more material contact area to grip the time-sert. In addition, the case-saver is a larger, coarser thread, which means that there is more material between each thread. More material translates into greater strength along the axis of the head stud. In simple terms, the case-saver creates a new hole for the head stud that is stronger and tougher than the original one in the case. Case-savers can still pull out of the case, however, this is usually only seen in high-stress, high-compression race motors, or if the engine has been overheated. Placing the case-savers in the magnesium case should make it more than strong enough for street and most race track use.

The 1978-89 engine cases were manufactured out of aluminum. Porsche realized that the magnesium cases, although lighter in weight, were more susceptible to the heat and stress of larger displacement engines. However, with the stronger case, arose a new point of failure for the infamous head studs. Attempting to better balance the stress of the engine from hot to cold, Porsche used a new steel alloy called Dilavar for the construction of its head studs on the exhaust side of the engine (intake and exhaust for 911 Turbo engines). These studs were designed to have tensile (strength) properties that were similar to the earlier steel studs, however, expanded and contracted more like an aluminum alloy. Matching the expansion and contraction properties of the Dilavar stud to the overall engine meant that the stress on the case, and the stress on the cam towers would be decreased.

It was a good plan, however, the strength of the Dilavar studs did not hold up. Particularly in harsh climates, the studs are prone to snapping and breaking. This occurred only on the lower row of head studs, because Porsche still used the standard steel ones for the upper row, with the exception of the Turbo engines which used Dilavar on both rows. The reasoning was that the temperature gradients on the exhaust side were much greater than on the top of the engine. The studs were somewhat susceptible to the environment. Condensation in the air combined with scratches on the studs can create small pockets of rust that form what are known as stress concentrations. The concept of stress concentrations can be easily explained by comparing it to the opening of a bag of potato chips. The bag itself cannot be easily torn or punctured, however at the top there is a small notch in the material that allows you to tear it open from that point. The v-shaped notch creates what is known as a stress concentration in the material, and makes it easier to break and shear the material apart. In a similar manner, rust or abrasions on the studs can create stress concentrations in the studs. It is not uncommon to see a broken head stud that has snapped at a rusty scratch on the surface.

Stress concentrations aside, the Dilavar studs were not robust enough to hold up to the stress exerted by the larger displacement 3.0L and 3.2L engines. So the big question that many people ask is “what stud do I use?” Based on the consensus of Porsche engine rebuilding experts that I've asked, it would seem that the original steel studs used on the early cars are the best bet for use in rebuilding any 1965-89 engine. It is very rare to see these original steel studs snap and break. They have also been used in many 3.0L and 3.2L engines without any reported problems.

Another solution to the head stud problem is to use aftermarket RaceWare or ARP head studs. These are aftermarket head studs that are very effective, and very strong, and also very expensive (about $550 per set). If you have the money, or are building a high compression race motor, then the RaceWare head stud set would be a good bet. However, in most cases, the early steel head studs should be more than adequate.

The repair procedure for the broken studs doesn’t involve a full rebuild, but instead can be performed only by removing the top end. Unfortunately, the top end accounts for about 80% of the engine, so if you’ve gone this far, you might as well tear down the bottom end as well. Removal of the old studs can be a big problem, as the aluminum case combined with the red Loctite used to install the studs creates a pretty tight grip. Special tools and a torch are required to remove the studs.

Okay, so you’ve read about the head studs. You’ve checked and you’ve found that you’re one of the many 911SC owners out there driving around with a broken lower head stud. Many 911 owners have a panic attack when they see this, and many Porsche mechanics will instantly recommend a full top-end rebuild to repair the stud. I have heard of engines that will run fine for a very long time with one or two broken head studs. However, the chances of further damaging increases if you drive the car with a broken head studs. While finding a broken head stud doesn’t mean that the car will be damaged if you drive it for another 100 miles or so, prolonged use of the car in this condition can cause irreversible damage to your cylinder heads and cylinders. If you find a broken head stud in your motor, then you should start planning for a rebuild in the very near future.

If two studs break on the same head, then it’s definitely time for an immediate rebuild. In addition, if you can hear an exhaust popping noise when accelerating, it’s time to rebuild. Driving the car with an exhaust leak can cause the head and cylinder to vibrate and knock against each other. If this problem is left unresolved, then the exhaust leak can end up damaging the head and the piston. In general, if you have an exhaust leak at the junction between the head and the cylinder, it’s best not to drive the car.

Reading Spark Plugs

The spark plug is really the best way to visually ‘see’ what is going on inside your combustion chamber. You need to pull out all of the spark plugs to perform a compression test, so you might as well take a close look at them while their out.

While today's modern fuels make plug-reading much more difficult, you can still glean a lot of information from looking at them. A good, well balanced engine will produce a plug that is light brown in color, and dry. If the engine is running too rich, the plug will often be coated with a lot of extra carbon. Keep in mind that the rest of your combustion chamber probably looks the same. An engine running too lean will have a powdery white coating on it, and the outer porcelain ring may have a burned appearance.

When reading spark plugs, pay close attention to the white porcelain ring around the plug. This white area will give you an excellent background to inspect the color of the plug, and to help determine how your combustion chamber looks inside.

If the plug is wet with oil, then that indicates that there is significant leakage into the combustion chamber past either the valve guides or the piston rings. This is generally a bad sign, and an indicator that your compression test may not yield good results.

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Comments and Suggestions:
Ivan Comments: Nick. I was just told it may be early wearing valve guides by observing slight occasional smoke while idling. Is there any certain way to tell? Is burning a quart of oil every 700 miles a definite indication to drop the engine. With 83,00 miles on my 1985 911, if it needs guides, should I do an entire rebuild?
October 9, 2016
  Followup from the Pelican Staff: Smoke idling may not be it then, most times smoke at idle accompanied by larger volume of smoke at decel. Applies to intake valves, exhaust valves won't always smoke.

You can check the valve guides by removing the cam covers, then removing the valve springs and measuring stem movement, side to side.

- Nick at Pelican Parts
 
Ivan Comments: I am the original owner of a 1985 911 German cab. with 83,000 miles I routinely changed the oil every 3000 miles. I don't drive it much past 8 years and in 2012 with 72, 500 miles it failed smog.. Despite attempts to try and get it to pass, it would not and I was forced to drive it to my other home in Idaho to register the car. 6 months later, noted some smoke mainly idling and was told possible early wearing valve guides. I began to drive it little more and it seemed to get slightly better but still would burn more oil. I know use about 1 quart every 650-700 miles. The car runs great and as strong as ever. I'm trying to decide what to do- do the tests and if seems be wearing valve guides, should I just rebuild the engine or just do the guides. I live in Burbank in Southern California. Do you know of a reputable shop to do the testing and the needed work?
October 8, 2016
  Followup from the Pelican Staff: if you were told the valve guides were worn, that is common, so starting there is not a bad idea. It may take care of your smog issues. - Nick at Pelican Parts  
merv the swerve Comments: I have recently bought a '97 993 carrera2 cab. with documented service records. When the engine is warmed up before & after the oil change mob. 1 15/50 I hear a tapping sound particularly between 2-3k revs. only when being driven and not when stationary revving the engine in neutral Any thoughts on the parts I will need to buy from you?!!
August 13, 2016
  Followup from the Pelican Staff: You may have lifter noise. They are hydraulic and non adjustable. once confirmed faulty, you will have to replace. - Nick at Pelican Parts  
Albert Blue 911T Comments: I recently purchased a '71 911T with approx 100K miles. It has been sitting since 1982. I went through the carbs, changed oil and filter, put in new plugs and got it running remainder of fuel system needs gone through so running from a gas can currently. It seems to idle and rev okay but carbs need further adjusting or has an air leak as I've got an intermittent pop though the carbs. Since it was sitting for so long I put some Marvel Oil down into the cylinders and rotated the crank by hand a few different times over a month. After running a few times it is still smoking pretty good. I removed the plugs and they look fairly clean. Compression has me concerned #1-128 #2-115 #3-130 #4-100 #5-110 #6-105. I've not ran the valves yet but wanted an opinion on the compression and smoke.
June 29, 2016
  Followup from the Pelican Staff: Compression numbers are bad, but you knew that. I would perform a leak down test to see if it is the rings of the valves. - Nick at Pelican Parts  
Chris G Comments: Hello, I am considering to purchase a 1987 911 Turbo. From the car fax I know the motor was "rebuilt" at 74,000 miles. It now has 79,000 miles and the current owner states he just had the motor rebuilt. I have two questions. i How many times can a 911 turbo motor be rebuilt before affecting the motor? ii Any idea why the motor needed to be rebuilt again with so few miles after the 1st rebuild? FYI the car did move from Texas to California - now in CA and rebuilt there Thank you
May 1, 2016
  Followup from the Pelican Staff: if rebuilt correctly, it should be refreshed and in like new condition. You are best off having a prepurchase inspection performed and asking for the details of the rebuild. - Nick at Pelican Parts  
Eyeguy Comments: If you have to rebuild an engine, 87 Carrera, at this point in time, with prices climbing. Are you better off keeping it stock or or go for more horse power?
April 28, 2016
  Followup from the Pelican Staff: Stock would be more affordable and easier. I would go with whatever fits your budget. - Nick at Pelican Parts  
craneboy Comments: Hello, I have a 2002 911 carrera with 67000 miles. I see where you said normally a Porsche burns about a quart every 1000 miles. I hadn't had this car but a couple of weeks and had to put a little more than two quarts in it already. I took it to a shop and had it checked out some and found other problems that will soon need fixing...brakes, ball joints and lower control arms left and right. Shame on me for not checking it out before I bought it. Trying to decide whether to keep it or get what i can out of it and cut my losses. Any suggestions? Thanx.
December 22, 2015
  Followup from the Pelican Staff: Burning that much oil, I would see what the vehicle needs. Could be an AOS which is no big deal. If major, you may not want to invest in the repair. That is up to you. - Nick at Pelican Parts  
Tim Comments: Great article! Thanks
My question: '78 911SC Targa 107,000 mi. Lightly driven for the past 25 years. Recently had valves adjusted and I'm not confident mechanic had enough experience w/ this model. Recently took to more experienced mechanic who discovered timing was off/8 degrees and # 5 cylinder was at 110 compression rest were in neighborhood of 130. Time to rebuild or can I drive as is w/ understanding performance will be diminished would I even notice?? or should I consider rebuilding?
December 19, 2015
  Followup from the Pelican Staff: Those compression readings sound like a timing error. Adjust the timing correctly and the numbers should return to normal. - Nick at Pelican Parts  
jimbob Comments: just received 3.0 case from xyz machine shop,case savers were installed,arp studs will not thread down to the 135mm specs. savers are flush with case,is it possible the savers were not installed deep enough in the case,please help
November 5, 2015
  Followup from the Pelican Staff: Possible. I would check with the machine shop. - Nick at Pelican Parts  
John V Comments: I have a 1981 Porsche 924 that the timing is way off. What is the procedure for removing and installing the Distributor. I had double checked everything else and when I go to start the engine it backfires. I have had mechanical experience with the Navy and a Cat Dealership so I do know more than the basics. I just can't get the timing correct, Please Help.
August 8, 2015
  Followup from the Pelican Staff: We don't currently have that tech article. If we get a chance to perform the procedure, we will be sure to document it.


See if this thread helps:
http://forums.pelicanparts.com/porsche-924-944-968-technical-forum/744961-1979-924-distributor-timing.html


I would grab a repair manual. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 
Joanne Comments: Wondering how long it is to replace an oil pan on a 1974 Porsche 914. Thanks
July 22, 2015
  Followup from the Pelican Staff: Depends on your experience. The small cover or do you want to reseal the crankcase?


I opened a post in our forums. A Pelican community member may be able to answer your question.
- Nick at Pelican Parts
 
Engapol Comments: I don't have a Porsche but this article does address the problem I'm having with my MB C320. It's only got 100,000 miles on it and it smokes for a few seconds on startup after the engine has been left to cool after running. It also happens when I suddenly open the throttle after cruising at a constant high speed e.g suddenly pushing it to 4000RPM on a motorway after being at 2500 for 20 minutes, accompanied by rough running while smoke is belching out. It's definitely not the head gaskets. Doesn't smoke on idle and when I'm driving in the city i.e constantly varying speed then there's no smoke while driving. The Smoke also sort of 'clears' after a quick burn, I can thrash it after it smokes and it'll be fine until oil leaks again I suppose.

Dealer said it was piston rings and that would require a rebuild, could it still be valve stem seals or guides?
January 15, 2015
  Followup from the Pelican Staff: Hard to say. ou can remove the intake and inspect the valves for signs of oil leaking. That is a good place to start. You could also perform a leak down test on the engine to test the rings. - Nick at Pelican Parts  
jmbro9 Comments: 86 911 Carrera has engine clatter, sounding like cam chain tensioner on cold start. As soon as warm, nice and quiet. Any ideas or suggestions?
October 20, 2014
  Followup from the Pelican Staff: I would start by checking oil level and pressure. Once you confirm lubrication is Ok, inspect the timing chain and guides. - Nick at Pelican Parts  
Aircooledboludo Comments: Hi , Excellent article , I am planning in buying a 1980 sc targa , the odometer reads 71.600 kms, I don't know if this is the second or 3 rd time around , seems little mileage for the wear on the body , the body is a good driver body , nothing exceptional ,I went today for a test ride , the car was cold and when they turn it on , there was a lot of white-gray smoke , for almost 5 minutes , it smelled oil , I know that smell , I took it for the ride and after 1 mile after I stopped there was a cloud of smoke from the back , runner it for 20 minutes , and the smoke from the exhaust was minimal , but there was a little when you revved it , the car is seldom used , and the price is $16.000 USD , my question is this , based on this price , will it be a good purchase even if a major rebuild will have to be done !?
September 27, 2014
  Followup from the Pelican Staff: This could be worn valve guides. I would have a shop check out the vehicle before you buy it. - Nick at Pelican Parts  
RUT Comments: I've got a 914 track car with a 2.7 six in it and got spun around backwards and fear I rotated the engine backwards in the process. Now I have a bad engine vibration and power loss at about 4500 rpm but it's intermittent. I've pulled the trans and the clutch assembly looks good. What do you suggest I do for next steps. Where should I begin looking con rods, crank, wrist pins, above the shoulders on the driver??
September 3, 2014
  Followup from the Pelican Staff: I would start by checking engine timing. if it is OK, compression and leak down. - Nick at Pelican Parts  
steveo Comments: Having trouble getting the cam nut loose from my 74 porsche911 is there a reason I can't break it loose or can you suggest how to make this job easier? please email at stevewestfall75@yahoo.com any suggestions
July 22, 2014
  Followup from the Pelican Staff: Are you using the sprocket wrench(counter-holding) tool? - Nick at Pelican Parts  
Fred Comments: I found a low mileage 86 911 for sale but during my test drive the Low pressure light comes on during idle. Is this a sign of bearing wear or is there another reason? Oil level is good.
July 16, 2014
  Followup from the Pelican Staff: Could be bearing wear or a faulty oil pump. - Nick at Pelican Parts  
GApilot Comments: I have a 1990 Carrera 4 964 that is smoking white after warm up, usually about 5-10 minutes. Can this be related to an oil over fill. When the car is level and cold 68 degrees where should the oil be on the dipstick? thanks
June 6, 2014
  Followup from the Pelican Staff: Oil should be between the marks on the dipstick. White smoke - coolant, black smoke - fuel , grey - engine oil. - Nick at Pelican Parts  
JonP Comments: Hi,
I have a 1974 911S, and I'm in Australia so exhaust has not had the problems of load from thermal reactors. Car uses hardly any oil, no exhaust smoke, just a few drips in the garage. However I am getting oil smoke in through the vents, quite bad at times, when driving. Any suggestions?
March 25, 2014
  Followup from the Pelican Staff: Likely a small oil leak, burning off before it hits the ground. i would inspect the engine for leaks. - Nick at Pelican Parts  
jay Comments: I have a 76 911s with 200k plus miles. My engine sputters and I also have a slight oil drip coming out the right exhaust. Is this a problem that can be solve without a rebuild????
March 3, 2014
  Followup from the Pelican Staff: Oil out of the exhaust is not a good sign. I would have the valve guides inspected, engine compression, etc. Once integrity of the engine is established, you will have direction for your repair. - Nick at Pelican Parts  
Dan Comments: '82 911SC with 185,000 miles
if it sits unused for 3-4 weeks it will puke a quart of oil overnight! reasonable dry until it "pukes". Normal smoke at start up, no smoke after it's warm.
What's happening??
January 22, 2014
  Followup from the Pelican Staff: When you say puke, it is leaking or burning? Could be bad valve guides or seals, bad rings. - Nick at Pelican Parts  
flyingscorpionjuanito Comments: How you doing

i have a 256 sc in my workshop, an i need to synchonized engine. to do have a pic of the cam and the crankshaft?

thanks

best regards
December 13, 2013
  Followup from the Pelican Staff: No I don't.
I would grab a repair manual. It will have the procedure, special tools and torque specs.
- Nick at Pelican Parts
 
JM993 Comments: I have a '96-993TT with about 24,000 kms on it. Previous life garage queen but as the secon owner I like to give her a good run. Previous owner did a full rebuild about 24 months back. No problems in my 2 years but I noticed recently some black or greyish smoke and a bit of a burning smell after a drive- lasts for a few minutes as the engine cools.

Thoughts?
November 23, 2013
  Followup from the Pelican Staff: Do you any oil on the ground? This could be an oil leak that burns off quickly. Check around the exhaust for signs of oil leaking onto it.- Nick at Pelican Parts  
LEE Comments: I HAVE A 1983 911SC. 188,900 NORMAL MILES.
THIS MORNING TEMP BEGAN RISING IN HEAVY TRAFFIC, ABOUT 210 ...230
ENGINE SHUT OFF, BUT, AFTER RESTART, THERE WAS BLUE AND WHITE SMOKE
AT IDLE THERE IS LITTLE SMOKE, UNTIL TAKE OFF AND WOW!!! BLUE SMOKE.
IS THIS A INDICATION OF BROKEN RINGS?
November 2, 2013
  Followup from the Pelican Staff: It depends on what color the smoke is. black smoke - fuel , grey - engine oil. You may have a broken ring or valve guide issues.- Nick at Pelican Parts  
poppajoe Comments: Hi,
I have a 98 996 with a 3.4 motor, it has reasonably high mileage 113k but has been looked after and well serviced. it is currently "in between services" and due for an oil change in around 4k miles.
I have recently been hearing a "tapping" on cold start up which goes as soon as warm or if revs are held a little off tickover when cold. Could this be tappets/valve clearances or would you say piston slap or small ends?

Any help would be appreciated.

Thanks, Steve
September 1, 2013
  Followup from the Pelican Staff: This could be a lifter noise. Hard to say without hearing. I would have it looked at by your Porsche mechanic. Just to be sure it isn't something major. - Nick at Pelican Parts  
Munga Comments: What a great article re the 911 yes/no engine re-build.I have a 1977 Carrera 3.0,that's done 207,000 kms since new,so it helped me to decide which way to go.
March 27, 2013
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  
Dean Comments: I have a 1960 T5B with an oil leak at the "V" groove where the oil cooler mounts to the engine case. This is a strong running just rebuilt engine with 2800 miles on it. It is now out of my 356 and on an engine stand.
I have heard these cracks can be fixed. Can these cracks be reliably fixed and if so, where?
March 27, 2013
  Followup from the Pelican Staff: You'll have to disassemble the engine, then the crack can be welded. - Nick at Pelican Parts  
dc Comments: I am buying a 1988 911 with 280000mi and the leak test showed 96% on all cylinders. Is that a good sign?
April 22, 2012
  Followup from the Pelican Staff: Yes, that is a good number. - Nick at Pelican Parts  
rbp Comments: I have a 1996 911/993. The info here seems to address up to mid 70's engines. Is there a seperate book/section for the newer engines or do these tech articles fit teh newer air cooled 993's?
November 30, 2011
  Followup from the Pelican Staff: 993 engines are different. I would grab a repair manual for your engine: https://www.pelicanparts.com/catalog/shopcart/911L/POR_911L_TOLbks_pg1.htm - Nick at Pelican Parts  
angee Comments: HI I have a 911 3.0L 1979 original motor. Low km's 74000. I removed the spark plugs and they were black coated with carbon. I was otld the mototr is running rich. How do you fix this problem? Thank you
November 1, 2011
  Followup from the Pelican Staff: You will have to determine the cause. Could be fuel pressure or volume related, or over-injection. - Nick at Pelican Parts  
frank Comments: Where is part II?
August 23, 2011
  Followup from the Pelican Staff: Right there - Click on "Click here to jump to Next Month's Article!" - Wayne at Pelican Parts  
redlizard Comments: Great insights here. You say 'The 1974-77 engines are decidedly the most unreliable of the bunch'. Does that also apply to the 77 Carrera 3.0 engine?
June 2, 2011
  Followup from the Pelican Staff: I think only the 2.7s are being referred to. - Nick at Pelican Parts  
Steve Comments: Hello there. I am considering buying a 911 with a 3.0 engine. I had a mechanic inspect it, who found it was fine except that one of the cylinders was showing a leak of 35% though compression was normal. The mechanic diagnosed this as valve guide wear. The engine has only done about 30k miles since the last rebuild and has done some racing during that time. Do you think this will require immediate attention, or will I be able to drive the car as it is for the time being?
January 27, 2011
  Followup from the Pelican Staff: Sure, you can drive the car, but power will be down, and oil consumption will be up. I wonder if they had the valve guides replace during the last "rebuild". It's definitely an issue, I would be sure to negotiate some type of price discount. - Wayne at Pelican Parts  
drjan Comments: I've got a 86 911turbo, with 175,000 miles. Uses 1 quart of oil every 3,000 miles, so pretty good. One tip. Have the timing chains and ramps replaced at 100,000 along with the rear wheel bearings. Keeps em running long.
November 10, 2010
  Followup from the Pelican Staff: Thanks for the additional info. We appreciate it.
- Nick at Pelican Parts
 
Galah Comments: i have black oil particles that come out of my 944 turbo, especially when the accelerator is pushed hard down. I also have to replace oil regularly. Also it shoots out flames as well ive been told by other car users. Is this normal ?Thanks in advance. I also now have a steering to the right problem, the car is extremely hard to turn right, left is ok though. any suggestions. thanks again.
October 29, 2010
  Followup from the Pelican Staff: Nope, not normal. Flames shooting out of the car indicate unburned fuel and/or a really rich mixture. I would run a compression check and/or leakdown test on the motor to assure that all the cylinders are properly compressing and firing. The steering problem may be a clogged line to the rack, or a worn out steering rack. - Wayne at Pelican Parts  
Mark Comments: Great article! Here's a question for you, I have a 1986 911 with 120k miles that smokes intermittantly. It may start-up and run fine and not smoke for days. Then again, it may start-up fine and start smoking within 5 to 10 minutes. It usually only smokes at idle after it is warmed-up good. I understand the valve guide and ring issues causing smoke but would those problems be intermittant?
Thanks, Mark
September 24, 2010
  Followup from the Pelican Staff: You may have some soot or carbon build-up on one of the valves. The intermittant smoking could be a sign that the engine is getting old and needs rebuilding. I would perform a compression check and a leakdown and see what those results tell you. - Wayne at Pelican Parts  
Bluzhnd Comments: Excellent article, now I have an idea what the symptoms of my engine are telling me and thing to look for when I get into the project.
June 15, 2009
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 

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