More questions on tensioners

[ricksmol]

I removed both cam chain tensioners from my '89 SHO. I was hearing a noise that seemed to come from the chain. Both of them show grooves on the plastic surface about 1/16" to 1/8" deep where the links ride on them. My question is this.. are these surfaces grooved from the factory or smooth when new? If smooth then how deep can the links go in before the tensioner is considered not suitable? Keep in mind these things are expensive.Also please how does one know if the chain is stretched? Looks great to me.
Rick

 

[Yamaha V6]

Flat when new.

Until it cuts through & makes metal to metal contact, leaving metal shavings in your engine.

If you're serious about the car, and you've got it open already, dump the $200 in the 2 chains & 2 tensioners & do it once. If you're not serious about the car, and the chain has decent tension, button it up. That's my advice, anyway.

 

[sdpatt]

You have described an excellent and minor wear pattern on the phenolic blocks on the timing chain tensioners. They have to wear some as they do their job and that amount on an '89 would be entirely acceptable. As long as the springs in the tensioners are functioning to maintain sufficient pressure on the chains, the tensioners are in very good shape.

Can you describe the noise you were hearing that made you think the timing chains were the source?

 

[ricksmol]

SDPATT:
Let me start from the beginning. A few weeks ago I started the car and it did something it never did in 13 years I owned it. It made a very strange metallic clanging noise as it tried to start. It lasted about two seconds and then stopped, the car started and ran normally. I noticed though that at high RPM's (4000 and over) under acceleration the car would buck untill I released the gas down to lower RPM's.(could a slack chain cause this problem by allowing timing differences between the intake and exhaust cams?)
Then about a week ago smoke started to come out of the exhaust and there are traces of oil from the front exhaust manifold?. When the car idles there is a noise coming from the rear driver's side of the engine.It sure sounds to me as a chain rattle of some kind .I took off as I mentioned the sprockets and chains and the tensioners ( I am also in the process of changing the valve seals in the exhaust valves).When I examined the head casting under the rear chain, I discovered a crack in the aluminium about 3/8" in length. I drpped some oil drops in there and they do disappear into the crack. I am now wondering if that is the source of the smoke. The spark plugs are clean, no oil on them at all. The car idled nice and smooth. I am tending to discount a broken piston ring because of the smooth idle and acceleration and the clean plugs.
I wondered if the chain did not hit the casting somehow causing it to crack. It is rather confusing so far. No definite clues to one particular problem.
Rick