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Replacing the Timing Chain Camshaft Sprocket
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Pelican Technical Article:

Replacing the Timing Chain Camshaft Sprocket

Mike Holloway


30 minutes30 mins


$50 to $350




22mm socket wrench, large flathead screwdriver, needle nose pliers, breaker bar (optional), torque wrench

Applicable Models:

Mercedes-Benz R107 (1972-89)

Parts Required:

Timing chain camshaft sprocket

Hot Tip:

Use a clean rag to protect chain and engine compartment

Performance Gain:

Proper chain tension and increased wear resistance

Complementary Modification:

Timing chain, chain guide, chain tensioner replacement

The Mercedes Benz 450SL is considered by many to be one of the most attractive cars Mercedes produced. It is a stylized combination of power, grace, and comfort and was sold under the model designation R107. At over 3,600 pounds and designed to meet (and actually exceed) strict safety regulations, the 450SL was nicknamed "der Panzerwagen", which means "the armored car", by the engineers who designed it. The 450SL was produced from 1973 through 1980, after which the R107 became known as the 280, 380 and 500 SL.

The SL variant was a two-seat convertible with a standard soft top and optional hardtop and optional folding seats for the rear bench. The designation SL derives from the German Sport Leicht, or Sport Lightweight and was first applied to the infamous Gull Wing 300SL. The 450SL was the third generation SL. The SLC (C107) derivative was a two-door hardtop coupe with normal rear seats. The SLC is commonly referred to as a 'SL coupe'. This was the first time that Mercedes-Benz had based a coupe on an SL convertible platform rather than on a sedan, replacing the 280 and 300 SE coupé.

The robust, V-8 powered SL is a joy to drive. Many drivers test the power of the 450SL. While the speed off the line is questionable, the top end performs smooth and responsive, giving the driver a sense of security. The 450SL cruises comfortably at speeds in excess of 75 mph.

One would think that when the engine is at speed there is a higher incidence of wear and eventual failure. This isn't necessarily true in the case of certain components, namely the timing chain. Chains, sprockets, gears and even bearings experience the most wear upon startup. The timing chain and the various components (guide rails, tensioning rail, chain tensioner) wear out after 100,000 miles and should be replaced. The sprockets should also be replaced. The chains can stretch but they also wear. As each rolling element of the link begins to experience wear it sets up for increased vibration and movement of the chain links and pins against the sprocket surface. As many teeth as the sprocket has, the chain has many more links. The sprocket surface wears down contributing to sloppy movement as the chain passes over the sprocket surfaces. This creates an even greater opportunity for chain breakage.

The guide rails will be the first order of business to address. In order to change the guide rails in preparation for the replacement of the timing chain, all the components in front will have to be removed. This includes the belts, pulleys, alternator, the distributor and the power steering pump were all removed. Please refer to these articles should you need edification.

I also removed the radiator. Normally you wouldn't have to do that but it was already out due to the development of another article. Refer to removing the radiator article for help in that regard.

Also, the distributor should be set at top dead center (TDC) and marked. This is needed when you put everything back. The distributor was also removed earlier. Hence, you can refer to that article if you need assistance.

The valve cover will have to be removed as well. In order to do that you will have to remove the air box. Refer to the valve cover removal article for help on how to do that project.

After the chain guide rails and the chain tensioner have been removed, the timing chain sprocket on the camshaft can now be removed. The crankcase sprocket will be removed later.

Use a large flathead screwdriver to keep the sprocket in place.
Figure 1

Use a large flathead screwdriver to keep the sprocket in place. Using a 22mm socket wrench, loosen and remove the bolt holding the sprocket in place.

be sure not to drop the washer into the engine.
Figure 2

be sure not to drop the washer into the engine. 

Place a clean rag over the covering in order to protect the engine from debris falling in.
Figure 3

Place a clean rag over the covering in order to protect the engine from debris falling in. Remove the sprocket and keep the chain secured with the rag and a screwdriver.

The sprocket is now free and can be replaced.
Figure 4

The sprocket is now free and can be replaced. Installation is the opposite of removal. 

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Comments and Suggestions:
Jim Comments: I was able to replace both sprockets without taking the guide rails or the chain off. It was quite easy. I did not have to remove the alternator but did have to remove the power steering pump in order to tap the new sprocket back on for the driver's side sprocket. I also removed the chain tentioner to replace it with a new one, but could have changed the sprockets without doing so. Next time in another 100000 I'll replace sprockets, chain, guide rails, and tensioner all at one time.
April 5, 2016
  Followup from the Pelican Staff: Thanks for sharing your installation process and experience. These type of comments add so much to the Pelican tech community.
- Nick at Pelican Parts
Jim Comments: Can you take the sprocket off without taking the guide rails out? A PO had the chain and guide rails replaced 2000 miles ago but did not replace the sprockets or the tensioner. I have the tensioner out. I'm also installing a 2 degree woodruff key on the passenger side camshaft. Actually, the sprockets look good, but I really don't know how to judge their wear. Would appreciate any thoughts.
Jim Bianchi
March 3, 2016
  Followup from the Pelican Staff: You may be able to unbolt it, however it will be difficult to get on and off. Follow the steps in the article for replacing the sprocket. - Nick at Pelican Parts  

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Page last updated: Mon 10/24/2016 02:44:02 AM