Hi all,

This is my last attempt to see if anyone has any insight into the issue I have had with my engine.

About a month and a half ago I pushed the engine pretty close to my set red limiter (54-5500 RPMs) in 5th gear (T5), going faster than I should have. later at a stop light I noticed a kind of hollow, yet sharp tapping noise.

It sounded like a stuck lifter, so the next day without hesitation I replaced all my lifters, and pushrods, and set, and re-set the valves to make sure they were perfect. The engine has about 37K on it since it was rebuilt, so I wasn't worried about hurting the cam with new lifters (considering I was planning to get a beefier cam in the near future) Started it up, and the sound was exactly the same.

I then used a stethoscope to narrow down where I believed the tapping noise was being emitted. Right around, and in the distributor it was loudest. I pulled the MSD HEI distributor and found the bearings were pretty well worn, but the gear looked FINE. I replaced the distributor with a brand new spare regular HEI distributor I had in storage, but the sound remained the same.

These are the most important facts about this issue:
1. The tapping does not hinder performance
2. The tapping takes about 20-30 seconds to get going from a cold start, and remains constant from idle to red line, engine cold or warm.
3. The oil comes out with NO metal shavings at all, after 3k and is barley starting to turn amber
4. With the ignition completely cut, car in gear coasting it still makes the sound.

I am at a loss... I would think if I spun a bearing I would have seen a decrease in performance, and at least metal shavings in the oil! Could it be my oil pump, running off the distributor? Oil pressure is perfect, and I have both an electric, and under hood analog oil pressure gauge.

Other facts:
1. In the mean time my fuel pump pushrod has been replaced
2. I pulled the tranny, and checked the flywheel for cracks. None found... Resurfaced, and reinstalled the tranny.

What it isn't for sure:
Headers are tight, no exhaust leak (again the sound can be heard when cranking, or coasting)
Anything in the ignition system with the exception being possibly a loose spark plug? (checked for tightness, and they all were tight)

Thanks for reading... I am about to pull my engine, so any insight would be very helpful. I would leave it, but it is quite embaressing at a stop light, and I don't want it to fail on me randomly.

Possibly a timing chain? (but it isn't being emitted near the cover)
Cam sliding? (wouldn't I see metal shavings?)

The major changes I have made to my setup in the last few months were a Holley double pumper, and the GM serpentine setup. Here is a pic for giggles before those were done.



Entire car... Why not?

 

Very nice ride! Can you post a vid?

 

how the oil pressure?and what kind of oil pump are you running?

 

Three Things ..........

First , Hello fellow Mass third gen owner !

Second , Nice looking car/engine , I can tell you've put a lot into it , and it shows

And third , , Any time I've heard the "sharp , Hollow rap" after an over rev , it's always been a wristpin ........

 

I have had one case where a brand new oil pump made a tapping noise that sounded alot like a wrist pin. I pulled the 500HP 454 and took it back to my machinist who in the case of that motor had done the assembly. He had come to the boat yard and listened to the noise with me. The motor was one of a pair in a 34ft Bayliner. We were both puzzled. Archie doesn't make many mistakes. After tearing down the motor and rechecking everything, Archie replaced the oil pump and the noise was gone. Melling paid for his time and mine on the redo. Melling is a kick *** company. Anyway, the oil pump is a definite possibility.

 

Ill let you know what I find out. Me and my friend just pulled his 355 out of his monte carlo and its doing the same thing you describe. Same loud tapping. We swapped the cam new lifters same ****. We thunk the piston is rocking in one of the bores maybe you broke a ring. It actually sounds like piston slap only louder and all the time. And its in the exact same area you have it. Builder pulling it apart tm. He has eagle sir rods and they have the bushed small ends on the rods. Hope it doesnt have anything to do with that. It sounds like a piston to me. Thats what his builder said it was. Could also be a oil pump too. Well know tm. Let you know soon as i do. As i know it was pissing him off enough to re pull it. Take care

 

Also check to see if the belt is stretched. Sometimes those tensioners go bad and they tap when there close to maxed out where it shows it needs a belt replacement.

 

if its by the distributor check your cam endplay probably a bit to loose.
Tighten it up some should go away.
Im plagued with something very similar, was suggested to me and makes perfect sense. .
Your cam is probably rocking back and forth some youre either hearing that or a lifter hitting the next lobe over just enough. Probably wont hurt anything
7-9 thou is good