Ktholin

A short while ago, I had my engine rebuilt (283 with solid lifters, 097 cam). I've put about 400 miles on it and it has been running fine. Recently, however, I've noticed a significant tapping noise which seemingly is coming from the right side of the motor. The noise gets louder upon acceleration.

I decided to check the valve lash, which was all over the place. The spec calls for 0.010 intake and 0.015 exhaust, and I found some intakes as high as 0.015 and some exhausts as much as 0.024.

I adjusted all of the valves to spec, and hoped that it would solve the problem. However, there was no change in the tapping sound. Any idea what the problem might be and what I should look at next?

Nowhere Man

does the heads have push in studs or screw in studs. double check them and that your rocker nuts are good. if those check out I would say your cam is going flat. have you checked your oil?

jimh_1962

Good oil pressure? If not could be a rod knock. Almost the same sound. But first check the studs. Maybe wiped cam... Worth taking apart the oil filter.

L78racer

could be bad fuel pump.

GTOguy

Stethescope time. Fuel pump, wrist pin, etc. You might try pulling ignition wires one at a time on that bank and see if the noise goes away. If so, it's a con rod bearing.

Ktholin

OK. I pulled the plug wires one by one and the sound goes away when I pulled the #4 wire. What does that indicate?

Easy Rhino

A bad lifter would not quieten up when you remove the spark, but a bad connecting rod big end bearing would.

Hope that's not your case. But if I had those symptoms I would park the car and drop the pan, and check #4 rod bearing (and all the rest while in there).

jimh_1962

Frankie the Fink

Hmmm...been a while but that's a test for rod knock... Not good.

Ktholin

What about a flattened cam lobe? Would that be possible? I'm puzzled why this would happen with a newly rebuilt motor. I've taken all precautions in breaking the motor in.

EAAR

Are you running oil with zinc in it? The older style flat tappet engines don't like the newer oils.

Ktholin

Yes, I am running it with zinc.

Frankie the Fink

If its been a 'short while' since the rebuild maybe you should pay a visit to the rebuilder and see what he/she says ?

jimh_1962

If it was me I would call the person who did the rebuild. Do not do anything more than what you have done so far. Heck, a flatten cam or not I would still talk to the engine builder first before do anything more. Let them diagnose the problem first then go from there. Do not do the tear down.

Incorrect rod bearing clearances.
Not torquing down the rod bearing caps to spec.
Re-using connecting rod studs.

Lots of reasons to what could cause it to happen...

cv67

ck your exh gaskets & have your builder look at it
did you use an old cam & lifters?

Ktholin

No, I had a new 097 cam and lifters installed. I will call the rebuilder tomorrow.

Why exhaust gaskets?

Randy G.

Exhaust leak on one cylinder can have different sounds. If you pulled a plug wire and it stopped and it was the gasket the cylinder wouldn't fire and the gasket wouldn't leak.

Ktholin

Thanks. That makes sense.

Frankie the Fink

Short of cam wear, I don't see any of the proposed causes changing the valve lash - there is still something going on there.

adurso19@yahoo.com

As to a flattened cam lobe, the rocker arm would have little movement and the engine would probably skip like you had a dead cylinder. Hope your engine built was warrantied.