Hello, I'm replacing the timing chain on my '88 300e and the timing marks don't line up. The key in the crank is straight up and down but the mark on the cam is off to the left (a little arrow pointing towards a small hole). As y'all can tell, I'm sorta new at this but I'm gonna be good!

Should I turn the crank alone to make the new chain match the sprockets exactly and leave the cam timing mark alone?

Should I turn the camshaft so that the timing mark is straight up and down?

Any help would be greatly appreciated.

put the crank on zero and the cam has a little hole behind the gear it should be lined up with a small nub on the front rocker tower, it should face straight up

Thanks Hiho, I've set the crank to Zero on the original chain. The cam gear has a little hole with an arrow pointing to it on the front of it. With the crank at zero, the key for the balancer is straight up in the 12:00 position. I'm pretty sure this is correct but again, the cam gear has the little hole on the front with the arrow pointing to it. It's in the 3:00 position. Am I missing something? Of course, the number 1 cylinder is all the way up at TDC.

if you have manual there is a good pic, I tried to download it to here but its to large. if you look straight down on the cam behind the gear there is the hole, there is a peg on the cam and a arrow on the cam gear that should be at 9:00 when the crank is at zero

Thanks hiho, I see the hole and peg but it is at 3:00 instead of 9:00 and the crank is at zero.

Does the cam make 2 revolutions to 1 revolution on the crank? If so, I'm good to go.

Just the opposite.
Cam is 1/2 the rpm of crank...

Unless you have ten hundred thousand miles on the car, why are you replacing the chain? It has been pretty well agreed upon by all the pros here that these chains are bullet proof.

Peter

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Auto Zentral Ltd.

I did change my chain while doing the valve job because it was about 31/2 degress retarted so even moving the gear the 3 degress it was just a hair retarted so now it is where it isupposed to be, the car has 140000 miles and should run great as the head i bought came with a cam, according to the book it has a couple more degress of duration( more power) can't wait to get it back on the road. if you have the disk it shows how the cam , chain and gears line up

That means that the head must have been surfaced which is why you may have to use an offset key.

Peter

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Auto Zentral Ltd.

the diesel uses a offset key not the 300e the head was machined so thats possible but its right on now. I wish it did have the key as I think I still have some from my old 300d

Off set keys don't care what fuel is used. They are only concerned with valve timing. If you want valve timing right on, set #1 according to factory specs and install the proper key according to crank position.

Peter

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Auto Zentral Ltd.

your right it does not care but there are two different designs the gas engine has a completly different designed gear thats not on a key but a pin this set up only only allows three options

It has been a few years since I've done a valve job on a 103 engine. The primary reason for a valve job on thses engines is to replace the worn out crappy guides. The heads are usually within .003 to .004 so they don't need machining. I'll have to check out group 05 in my M103 book today to see about the keys. You may have me on this one.

Peter

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Auto Zentral Ltd.

Just a tip for any M103 owner who wants to change valve seals with the head on. You don't need to buy the special M103 spring depresser if you have one for earlier gas engines. Go to a wrecking yard and grab a rocker assy off of a dead M103. Strip off and loose the rockers and bolt this assy on your engine after you've removed your rocker assy. It makes a perfect fulcrum for your valve tool.

Peter

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Auto Zentral Ltd.

I bought a small compressor that just clamped the spring and pulls it together, only $20 bucks from northern auto parts, but I like the idea and I had a extra rocker assembly, the springs don't really have a lot of spring tension for the rpm, mine was only about 90 lbs. so I shimmed it up to 110 to make me feel better