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Pelican Technical Article:

Valve Adjustment

Time:

3 hr

Tab:

$20

Talent:

**

Tools:

24mm socket, 13mm wrench, Valve adjust tool, adjustable mirror, spark plug socket

Applicable Models:

Porsche 911 (1965-89)
Porsche 930 Turbo (1976-89)

Parts Required:

Valve cover gaskets & hardware

Hot Tip:

Use a shop light, and disconnect hoses that get in your way

Performance Gain:

Greater horsepower, and quieter valve train

Complementary Modification:

Change Oil, Upgrade to Turbo Valve Covers
101 Projects for Your Porsche 911

This article is one in a series that have been released in conjunction with Wayne's book, 101 Projects for Your Porsche 911. The book contains 240 pages of full color projects detailing everything from performance mods to changing your brake pads. With more than 650+ full-color glossy photos accompanying extensive step-by-step procedures, this book is required reading in any Porsche 911 owner's collection. See The Official Book Website for more details.

One of the most common and expensive maintenance tasks on the 911 is the adjustment of the valves. I recommended that the valves be adjusted about every 10,000 miles on the later model 911s (1978 on), and about every 6,000 miles for cars manufactured prior to 1978. If your valve clearances are too tight, then your valves might not be closing all the way, and you will not obtain optimum performance. Likewise, if the clearances are too loose, your valves will not open all the way, and you will also have a very noisy valve train.

Before adjusting the valves, make sure the engine is stone cold. Adjusting the valves on even a warm engine will result in inaccurate settings. Don't start the engine for four hours before adjusting the valves; letting it sit overnight is better. The first step in the valve adjustment process is to disconnect the spark plug wires, and remove the distributor cap. You don't need to disconnect the plug wires from the distributor cap. I also recommend that you remove the spark plugs during the process and replace them with new ones when you're finished. You may need a deep spark plug socket to get at all of the plugs. See Project 22 for more details. Now, remove the valve covers from both the top and the bottom of the engine. You may need some extensions to get to all of the nuts: it gets pretty tight both on the top and the bottom. I recommend emptying the oil out of the engine before you remove the lower valve covers. If you don't then you might have a slight mess on your hands.

After the valve covers are removed, you need to set the engine at Top Dead Center (TDC) for piston number one. This corresponds to the point where the Z1 mark on the crankshaft engine pulley lines up with the split in the case, and the rotor on the distributor is pointing at the little notch in its housing. You can rotate the engine by placing a 24mm socket on the fan pulley nut and turning the engine clockwise. Make sure that you don't turn the engine counter-clockwise, as that may end up damaging some of the chain tensioner parts. If the engine doesn't turn and the belt slips, then you might have to replace or retighten your fan belt (Pelican Technical Article: Fan Belt Replacement). Removing the spark plugs and placing the transmission in neutral will help to ease the amount of force required to turn the engine.

When the engine is at TDC for piston #1, it's time to adjust the valves for that cylinder. Both the intake and the exhaust valves can be adjusted at the same time. The intake valves are located on the top of the engine inside the engine compartment, and the exhaust valves are located underneath the engine. For each valve, loosen the 13mm retaining nut around the adjustment screw, and turn the screw back counter clockwise. Now, place the valve adjustment tool in-between the valve and the swivel-foot screw, and tighten down the screw. A light coat of engine oil on the feeler gauge blade helps you feel when the adjustment is correct. When the feeler gauge has been tightened down upon, tighten up the retaining screw while holding the adjustment screw steady using a screwdriver. Recheck the clearance after you tighten up the screws, as they have a tendency to move when the retaining nut is retightened.

Now, rotate the engine crankshaft 120 degrees using the fan pulley. There is a mark on the crankshaft engine pulley that will indicate the 120 degree position. Now, repeat the adjustment procedure for cylinder number six. When finished, rotate the engine another 120 degrees, and adjust the valves for cylinder number 2. Repeat the rotation and adjustment procedures for the remaining valves following the engine firing order 1-6-2-4-3-5.

When you are finished, rotate the engine back to TDC for cylinder number one, and the rotor on the distributor should be pointing at the notch in the housing. Now, go back through the rotation procedure and check the clearance of all the valves using the feeler gauge. If any feel too tight or too loose, then repeat the adjustment procedure for that valve.

When the whole process is complete, replace the valve covers and tighten them to about 8 ft-lbs (10.8 Nm). Make sure that you use new valve cover gaskets and mounting hardware when you are replacing them. Following the valve adjustment procedure, you might feel a significant increase in power, and a significant decrease in the valve train noise.

A 24mm socket and wrench is the best way to rotate the motor.
Figure 1

A 24mm socket and wrench is the best way to rotate the motor. Make sure that you only rotate it clockwise, as rotating it significantly in the other direction can result in damage to the chain tensioning system. Make sure that your pulley and fan belt are tight prior to turning the motor, or the belt will slip on the pulleys. Removing the spark plugs, and placing the transmission in neutral prior to turning the engine decreases the amount of force required to rotate the engine.

The crankshaft pulley has a mark of Z1 (shown by arrow), referring to top dead center for either cylinder 1 or 4.
Figure 2

The crankshaft pulley has a mark of Z1 (shown by arrow), referring to top dead center for either cylinder 1 or 4. When the crankshaft is lined up with this mark and the distributor is lined up with the notch in its housing, the motor is at Top Dead Center (TDC). In the combustion cycle, the spark plug has just fired, and both the intake and exhaust valves are closed.

The distributor must be pointing to the small notch in the distributor housing (shown by arrow) in order to make sure that the engine is at Top Dead Center (TDC) for cylinder number 1.
Figure 3

The distributor must be pointing to the small notch in the distributor housing (shown by arrow) in order to make sure that the engine is at Top Dead Center (TDC) for cylinder number 1. At this point, both valves are closed, and the rocker arm feet should have a physical gap between them and the top of the valve.

The special feeler gauge is an important tool in the adjustment process.
Figure 4

The special feeler gauge is an important tool in the adjustment process. Normal feeler gauges will not fit well down into the recess of the cam tower. Make sure that you adjust the valve so that you can still easily remove the feeler gauge from between the foot and the valve. Also make sure that you have a few extra feeler gauge blades handy, as they are very easy to break when you are reaching around into the recesses of the engine.

Use a 13mm wrench and a screwdriver to tighten up the adjustment screw-foot.
Figure 5

Use a 13mm wrench and a screwdriver to tighten up the adjustment screw-foot. Make sure that you double-check the clearance after you finish by removing and re-inserting the feeler gauge.

The firing order for the 911 engine is 1-6-2-4-3-5.
Figure 6

The firing order for the 911 engine is 1-6-2-4-3-5. Adjust both the intake and exhaust valves together in this sequence, and then go back and check all the clearances again. Sometimes the rocker arms seat slightly differently the second time around.

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Comments and Suggestions:
Frank Comments: Thought i would share what i learned as a complete noob doing this for the first time. Thanks of course to Wayne and pp for this article.

1. I spent 2 nights and was nearly driven to tears attempting to put the feeler in the gap without success on any valve. I thought it was me and decided to give up and send to a mechanic. he quoted me $1000 *just to do the valve job*. I got doubly motivated then.
2. as a last resort i loosened the nut and the valve screw on each valve, and pulled up on the valve to loosen it up further, before trying to slip the feeler gauge in. Aha, there was the elusive gap I had spent 2 nights trying to find!
3. after finding the gap, then i tightened up the screw to find that "magnetic drag" on the feeler.
4. here's why i couldn't find the gap the first go round: My p-car 89 targa 3.2 i inherited from my dad who best as i can tell *never* did a valve job in 26 years. valves get tighter over time, not looser - from what i read anyway.
September 27, 2015
  Followup from the Pelican Staff: Thanks for sharing your experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
 
Speed Comments: My question is how to adjust the valve timing after a complete engine overhaul .
The problem is that you start with adjusting the camshaft on the left side cylinder 1 side , but what to do with the camshaft on the right side cylinder 6 side.
How can I avoid an piston to valve collision when I turn the engine over to adjust the next valve, in this case the number 6 valve
April 14, 2015
  Followup from the Pelican Staff: Start with cyl 1 with cyl 4 at overlap. Then do the following cylinders, moving through TDC and overlap positions. This is a brief description. 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
 
Turkey Comments: You have done a very good job with your part store and all your programs John Harrison
December 9, 2014
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help. - Nick at Pelican Parts  
HOSER Comments: AWESOME ARTICLE, WILL DEFINITELY BE PURCHASING THE 911 ENGINE BOOK FOR MY FUTURE ENDEAVORS.

THANKS

JOE
November 12, 2013
  Followup from the Pelican Staff: Thanks for the kudos - Kerry at Pelican Parts  

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