307 tapping thoughts?

[techg8]

Here is video of the tapping of my 307 I have been describing

http://www.youtube.com/watch?v=w4HPE79Eq34

It sounds a lot lighter in the video than in person.

 

[Bonnewagon]

I can see where that would be annoying. Being that it is tapping while not under any load disqualifies some stuff, like EGR, or any other compression related problem. It sounds like something valvetrain related. Did you re-use the lifters?

 

[techg8]

It really is louder in person. sounds like a ball peen hammer tapping away inside the engine. I am not comfortable driving it. In the vid it sounds a lot like rockers

I did reuse the lifters but one of the 1st things I did when chasing this down was remove and disassemble all of them, cleanup and reassemble. Nothing was broken.

Then I noticed that the tapping goes away when I remove the #8 plug wire. So at that point I discounted the lifters and valvetrain.

I discount wristpin issues because it does not get worse with load and only appears at light throttle.

Its got to be piston slap, or some sort of detonation due to spark.

Trouble now is trying to discern which.

 

[pontiacgp]

the bolts on your flex plate are all tight?

 

[Bonnewagon]

I think you can eliminate detonation as it happens with no load. I'm wondering what could be with #8 that would go away with pulling the plug wire. A bearing would only get worse as rpm's rose, and piston slap usually goes away as the piston heats up and expands.

 

[techg8]

well i am kind of stumped.

I do remember #8 being the roughest cylinder of them all when I honed it. the walls werent perfect.

 

[techg8]

UPDATE:

It warmed up a bit and I lifted the engne to pull the oil pan and have a look at the rod bearing on #8

Sure enough it is chewed up.

Not like I put the cap on backwards, but like something came out of the crank lube hole and chewed its way out.

The crank is OK because I stopped driving it mostly. I should be able to smooth it enough to be good.

I am going to let it sit a day or two then have a look at the other bearings while I am there. I will have a look at an oiling diagram as well to see where stuff may have come from or gone.

Whoever guessed Rod Knock, you were right.

 

[hurst1979olds]

If there is no groove on the crank you should be fine, some fine emery just to get any minor imperfections out and slap new bearings in it. What I've done before is use .001 bearings. It will give you a tighter clearance. They work good. But that is only if your crank has never been ground. If it were me I would also put a new oil pump and screen on it. Since you there anyways. My wife jeep had a slight rod knock. I put .001's in it and a HV pump and it runs great now....What was your oil pressure? Did it bounce around alot or was it steady?

 

[techg8]

the oil pressure was ? I only had an idiot light hooked up, and it never went on. The bearing was pretty wasted though.

I thought about it a little bit and decided to use this as an excuse to pull the 307 and drop in my Buick 350 that I had sitting on a stand.

I probably will part and scrap the 307