PeachParts Mercedes-Benz Forum - View Single Post - bend a valve by being one tooth off on the chain?

troylatif · #15 05-17-2008, 10:42 PM

I would have to agree with the post that mentions stuck valves. If a valve is stuck, then sure it'll collide unexpectedly.

I had this experience in rebuilding my m110 in my w123 280e. In the end I just took it to a shop with all the new guides, valves, and grease of choice, and let them have at it. Came out real nice.

But with regard to timing, I'd say your best bet is to get the no 1 piston at TDC before setting the valve train over it. In that case, I'd take a depth gauge and get the true TDC position. You'd be miraculously suprised at how the TDC on the damper is even ~0.3 degrees off due to deformation in the disc material or in the mounting hub. I was quite surprised that a slight hot burning issue was caused by none other than a 0.3 degree offset from the true TDC. That was after getting the whole thing put together!

Anyways, yes, you can get valve piston collisions due to a misplaced chain. Check the specs on your engine so as to when the intake and exhaust both open and close. Take your cam gear and measure the radius. Get the circumference. Take the link to link distance, and then divide the gear circ. by the link to link distance. This is how many links can sit on the gear. Then divide 360 degrees by that number and this is how many degrees offset you will have as a result of misplacing the chain by one link. CHeck this against your "valve opens at" measurement and there you have your answer.

If the calculation gives you a number that is greater than your book's number, then you very well could have bent valves this way. I bent 4 intake and exhaust that way before saying "f' it, i'm buying all new valves and sending it to a pro".

-Troy