383 tapping noise

[c1500sbc]

I have this tapping noise I can’t quite figure out. It sounds similar to a rocker out of adjustment, but I’ve adjusted them and the noise continues. I can loosen each rocker and get the very noticeable clattering it makes, tighten it down until that clattering goes away, and then I go a half turn past zero lash. But the tapping noise, separate than the clatter noise of the loose rocker, is still there. This is a hydraulic roller cam. It certainly sounds loudest around the driver valve cover. Manual transmission so no flex plate. I removed the supercharger belt and the accessory drive belt to confirm it wasn’t an accessory. I poked around with a stethoscope and it’s definitely not a lower end noise. If it were a collapsed lifter, it wouldn’t make a separate noise from the valve adjustment, would it? The noise seems to follow engine rpm but either gets drowned out or goes away as rpm increases. Oil pressure is great and vacuum seems pretty steady for the cam specs. Any thoughts? Sorry for the quality!

https://youtu.be/_3OoXkTRGlU

[BOOT]

Good call on pulling the belt to rule out any accessory. Seen a turbo engine that the guy couldn't find anything else wrong, turned out to be a broken ring.

[c1500sbc]

Similar noise ended up being a piston ring? Weird for sure.

I was thinking maybe it’s a wrist pin?

[BOOT]

Could try and get a look at the bores(piston down) on that side with a scope, it messed up part of the bore were the ring broke off.

[HQM383]

Pushrod side of rocker rubbing on rocker cover?

[c1500sbc]

Pushrod side of rocker rubbing on rocker cover?

I ruled that out too unfortunately. It does it with the valve cover off also.

[mag2555]

A bad wrist pin makes a double slap noise, at the top and bottom of the stroke.

I would be cutting my oil filter open real soon to look for crap and what might be magnetic or not if crap is found.

[BillK]

I know of several guys that have been fooled by an exhaust leak. They can sound just like a valve train noise.

[BOOT]

I know of several guys that have been fooled by an exhaust leak. They can sound just like a valve train noise.

I agree a lot are But sometimes they aren't, one that I thought was a exh leak turned out to be a cam bearing https://youtu.be/f2fbgn4aYFA

[mag2555]

You can pull off one plug wire at a time and listen for a change.
If it goes away then you have a rod Bearing issue.

[Tom Walker]

Worn rocker arm?

[F-BIRD'88]

hyd lifters are sensitive to what motor oil you use.
Noise....
try Shell Rotella T 15w-40

[F-BIRD'88]

Now you can throw together that killer low cr junkyard 305 sbc.
(cammed+ Ported 350 heads). and boost the hell out of it. while you fix the wounded 383.
The lower the cr the better on the blower friendly 305.

[rfoll]

A loose valve guide will make a tapping noise.

[c1500sbc]

So the motors out now. I’ve Done it enough times I can get the motor on the ground in two hours. Prior to that I determined it’s coming from the side of the block. Not the lower end and not the upper but right where a wrist pin would be. Sounded like a double tap. I did pull the spark plugs and look in the cylinders with a borescope and did not see anything at all. The cylinder walls still have hashmarks in them though which is a great sign. I’ll get the motor torn down tomorrow and I’ll keep y’all posted. I did find some -22 cc pistons I believe for a 383.That would put me in the high eights for compression ratio. I may just go that route and change out the camshaft to a more blower friendly spec.