M42 timing chain

[Hick]

thats one thing to replace.... do it all... if the teeth on the cam gears are pointy, then they are bad. there should be a flat top about an 1/8" wide.

like this, and any gear:


tensioner rail, guide rail, lower guide, crank oil seal, tensioner, cam gears, chain.

the reason behind the engine failure is a jumped chain. only the intake valves bent?

[SiGmA_X]

I have shop cost for all parts. What all is recommended to replace? Does anyone have high res pics of good vs bad gears, because if I hadn't read about "bad gears" online, I would assume they are fine, they sure look fine.

Why not replace the chain? Is it the gears that cause the chain to lose tension? The tensioner seems to be okay, actually, but those are hard to gauge without replacing and seeing how things sound.

[Hick]

REPLACE THE CAM GEARS!

[wolfgangstbd]

while your in there you might as well replace all of it. but you dont really have to replace the chain. i think there are a few websites that sell the service kit

[SiGmA_X]

Afternoon folks,

My girlfriend bought a 91 318 with engine trouble. Doesn't run, nasty chain noises from the PO. I took the valve cover off and there was a LOT of chain slop, it could move perhaps 2 teeth. Appears the tensioner wasn't doing its job. I convinced it back to proper timing (BTW, is there a front of engine TDC mark, as the flywheel has no hole.. And its stock according to my service history..) and did a leakdown, #1-3 95%, #4 40%. Pulled the head, the valves are obviously bent, its going to be sent out to be rebuilt (surface, new guides/seals, replace needed valves, valve grind).

So, in regards to the chain, do I want to just put a new tensioner piston in, or should I pull the lower cover and replace the chain too? The guides have minor wear (180k on the car IIRC), so I don't think they failed...

Any input is well appreciated!

-Roman