Recently acquired a 1970 280 SL/8 (113.044 & 130.983 engine) with approx 145K miles. Compression is good in all cylinders and vehicle runs well (but rich). Service records indicate that cylinder head has been replaced at least twice and camshaft once, due to blown head gasket & overheating. Prior services have been performed by non-Mercedes techs (Shell service station!)

While inspecting valve clearances, noticed that when the cam timing notch is aligned with mark on cam support tower, crank timing reads 5-6 degrees ATDC.

Timing chain does not appear to be stretched (chain is taut over top of cam sprocket) nor is cam sprocket worn. Chain tensioner is functioning and there is no indication of chain slap at start-up. Eyeballing cam suggests that loosening chain and advancing 1 sprocket tooth would overcorrect problem. Crank timing disc and pointer appear to be correct for engine. M-B states that offset Woodruff keys are not available for this engine.

Any suggestions on how to rectify this problem? Thanks in advance!

JGL

When using the cam mark and crank TDC method to check the chain, it is of the
utmost importance to turn the engine over by hand from the crank damper bolt in the normal
RUNNING direction. It can be turned the other direction, but that will give a false reading as you are then pulling from the chain tensioner slack side.
Although off-set keys can correct these,
it is much easier to change a streched chain with a new one with a repair link.
The link is connected to the old chain and
pulled around the gears by the old one . The link is then refitted to the new chain. Fairly simple.
As you mentioned that there has been a couple of head jobs done , there is also a possibility that someone may have shaved the head, which could could change the distance between the cam and crank, resulting in your reading. Others may know more on that.
PS.
As a good test for a worn chain, be it any chain,is to turn it sideways held out-streched and see how much it droops on the far end.
Compare to the new one before installing and it will give you an indication as to the difference in condition.
As these 113 are mechanical FI, your pump is
also timed by this chain and a worn chain directly affects the the fuel metering, so
that is another reason, aside from valve timing, to change the chain out when they show any wear.

I am surprised that MB (?) says that offset keys are not available. I have a 250SL, M129 engine, and have checked and adjusted the cam timing using offset keys obtained from a dealer. Perhaos the guys at the Partsshop can help, or one of the specialists like SL Tech in Maine, or S & S in Texas, or Star Quality in NY. I used the procedure outlined in the Factory Repair Maunals for passenger cars up 1959 and up AND the 1968 and up 108-109-113 chassis cars (the /8 cars). My chain was retarded about 2 degress with about 17,000 miles on it. I'm pretty sure this was not a wear issue, but an individual tolerance issue. The process for checking the valve timing is not complicated, but requires a good understanding and good measuring tools. Your best bet may be to find someone who actually still knows something about these cars (rare at a dealer these days). Afetr all, the cars are 30+ years old now.

Mercedes says that +or- 4 degrees is normal and should not warrant repair on a gasoline engine. (this is from the repair manual on the 16v)

------------------
Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

Good point Benzmac. I checked the cam timing on my 250SL for reference. After finding it retarded 2 degrees, measured by a degree wheel on the cam, I reset the cam timing (advanced it) to enhance the engine's torque characteristics. The old sixes were relatively weak in that area.

Another point that I am wondering about, considering all the posts regarding timing chains and the crankshaft/cam pointers being X degrees out of line is: are they talking about degrees at the crankshaft? The cam is off half as much, so 6 degrees at the crankshaft is not unreasonable nor should it require correction unless one wishes to fine tune the motor.

Don't confuse a few degrees out on a newer tech auto to one that depends strickly on Mechanical linking of the valve, distributor, FI pump and linkage geometric timing. There is no computer to change the spark, richen the mix via a sensor[o2], etc.
All of these on 113 are factory set using mechanical calculations and are all dependant
on correct timing which starts with the timing chain. If anything, this is more
critical than on a computer controled system.

FYI -

Initially told by M-B and Bud's Benz that no offset keys were available for M130 camshaft. Dug up the following numbers from the 108/109/111/113 Service Manual and was able to obtain the appropriate key afterall.


* 621 991 04 67
(for 4 degree crank correction)


* 621 991 02 67
(for 6.5 degree crank correction)


* 621 991 01 67
(for 8 degree crank correction)


* 621 991 00 67
(for 10 degree crank correction)



[This message has been edited by jgl1 (edited 04-05-2000).]