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Old 04-05-2004, 12:09 AM
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Join Date: Mar 2003
Location: Los Angeles, CA
Posts: 445
Left cam is 5 BTDC & right cam is 5 ATDC

Finally got most of the timing stuff together on my '72 450SL; replaced the chain (rolled it in), tensioner, 3 upper side rails, tensioner rail and both camshaft sprockets. The really odd thing is that the timing is 10degrees apart between the left and right camshafts. The left (driver side) cam aligns with the tower 5 BTDC! But the right cam is 5 ATDC. The woddruff keys are not offset. The car has over 200,000 miles.

It is clear that neither cam is off by a tooth. Off by one tooth is 10 (36 teeth in the sprocket). It is kind of suspicious that I am 10 off between the left and right cam though.

Could one of the sprockets besides the cam ones (EG the idler sprocket) get worn down enough to create a 10 problem? Or could it be something else like different cylinder head thickness? I'm sure the two head gaskets are the same thickness (I changed them 100k miles ago).

Finally, with or without knowing the cause should i get offset keys for both cams. Is it not worth it to get serious with a dial indicator, measuring 2mm lift on the valves and then reading the exact crank pointer mark. All this to fix approximately 5 BTDC on the left cam and 5 ATDC on the right cam.

I hope someone with more experience can help me.

Here is an update:
I decided to measure the cam timing the shop manual way. I set the #1 and #6 valve to zero cleareance and set up my dial indicator. When the #1 intake began compressing and moved 2mm vertically the crankshaft recorded 2 ATDC. For the same procedure on the #6 intake valve I read 3 ATDC. These seem like very reasonable numbers. I wonder if this prooves that timing the camshaft by ligning up the markings on the cam can not be trusted for evaluating the cam timing and chain stretch. I believe Stevebfl wrote that the cam marks are there only to make sure you didn't skip a tooth, not for timing the camshaft. If I hadn't done the dial indicator thing I may have bought offset keys and made a correction based on incorrect findings.

Could someone tell me what degree it should be for 52/53 cams in a 117.982 engine and if my latest measurements are good enough? Oddlty enough my factory manual does not give this info for the stock engine in my 1972 450SL (I have 52/53 cams in a 117.982 engine).

1972 450SL
1982 300D Turbo

Last edited by erubin; 04-05-2004 at 07:13 AM.
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