swerks

86 turbo RTE engine sounds like a load of marbles bouncing around the valve cover when I let off the throttle. this noise is not noticable from inside the truck and it seems to be running well. rebuilt engine with about 7000 mi on it. Should I be worried ? what causes this noise ? I never noticed the noise before, but had not played with the throttle under the hood till now.

cutboggers

Valves??? maybe have they been adjusted since rebuild?

swerks

I was thinking that may be it, that or the timing chain but both were done 7000 mi ago.

cutboggers

Do you have enough oil pressure?

iam_turner

I've heard noise like this before - it ended up that there was bad gas - diesel in the gas can cause pinging like sounds.

How is the timing?

taandctran

It could have something to do with it being a turbo.... I know you are supposed to run high octane in the modern turbo engines.... I dont know if this is true for the early turbo motors. It causes the engine to spark knock. I think it is becouse of a bad air/fuel ratio.

Noltz

Nah.. that would occur under boost, not decel. Good thought though. I would go with valves or your timing chain tensioner has loosened off. Definitely get it checked though - that kind of noise is cheaper to fix BEFORE whatever's loose flat out breaks.

taandctran

Yeah after I think about you are right... It would only happen under boost. but he did say he was playing with the throttle under the hood. That would make the turbo pressurize right???? but it wouldn't make the engine "bog down" like it had a load on it.... I think that is when it would most likely spark knock.... And it proably has a sensor for that anyway. Right?

cutboggers

yessum

swerks

I run premium fuel