After trying to set a new timing mark on my harmonic balancer (ring had slipped), I had taken a spring rod into the #1 cylinder and tapped the engine over until I was at TDC - Unfortunately, the spring got stuck and I had to get under the car and turn the engine back via the flywheel. This freed up the spring rod and I was able to pull if from the cylinder (no lectures necessary - learned this lesson the hard way). When I put everything back and started the engine I had a knock for a few seconds. I thought for sure I bent a push rod.

I've pulled the valve cover and checked for bent push rods - all look good. I adjusted the valves and still have the knock. The knock seems noticable only when first starting up and then after letting off the gas and it returns to idle. That's when it's most noticable. It's not continuous! I have used a stethoscope and can't quite pin point the fricken problem.

Any advice on narrowing the possabilities??

 

Just got back inside from putting the valve cover back on and running a couple more tests. When I first start the car and it's in open loop with a little higher then normal idle, the engine sounds perfect. Once it goes into closed loop and idle drops back to about 450 rpm, the knock is there.

I took off the #1 plug wire and ran it again. Noise is much less if at all. Plug wire back on - and there it is. When I bring the rpms up the noice is much less pronounced if at all. Can't tell for sure if it's there with or without the stethoscope, to much other noise. Either way it's definately not a knocking noise at that point. But at a low idle - its a knocken!

 

Well, a little more information in case anyone reads this and has a clue on what's going on.

Put the stethoscope all over the engine. The noise is definately coming from #1 cylinder. I hear the noise through the header, block and intake manifold around that cylinder. Fades from there out. Again, the noise fades with increased RPM, even when using the stethoscope, only time it really knocks hard is at low idle. Oil pressure looks real good - any chance I damaged the lifter? Wouldn't I have changed the noise while adjusting the valves, if it were a lifter?

 

Well, 450 rpm is too slow an idle for a V8. It may not be getting enough oil to a particular wrist pin or something at that speed. 750 to 800 rpm in neutral is a much better idle setting.

 

That was a typo, sorry. At 1000 rpm it sounds smooth, when it drops to 750 the knock is obvious. The engine has about 10k miles on it and is clean as a whistle. Oil pressure is real good.

 

Knock is getting worse! But again, really only noticable at idle and it appears to go away with the plug wire off.

It's a knock, not a tap.

ANYONE???????