So I bought a 91' firebird and it had a slight knock after it was fully warmed up. I pulled the intake manifold to see if it was a lifter, valve spring or rocker arm and all of those were fine. Everything's back together and now when I start it up it makes a loud *** tapping noise that sounds like it's coming from the upper passenger side of the engine. Any ideas? Also, would a bad exhaust leak have anything to do with this *** **** noise?

 

since you didnt get any replys..maybe give us a little more info.Like did you adjust/remove/install anything when you had the intake off or V/cover off?.I would guess its misadjusted valve lash...it also sounds like you might have a collapsed lifter...meaning one or so lifters isnt pumping up.You could try an additive or thicker oil and see if it gets quiet or to a lesser degree of noise to kinda narrow it down.

 

I have a simmilar noise (sorry cant say same without hearing yours) on my '91 3.1 and it's a loose wrist pin. It sounds just like a lifter/valvetrain noise except when you tap the throttle it changes frequencies.

 

Very true fictmich...it could be that too..I had a 68 bird with a piston pin tick and it would go away with a additive for a few weeks and then come back but I ran the crap out that motor with it making noise like that and it never blew..sold the car with it still making noise.

I wanted to add something..if I recall I pulled one plug wire at a time to narrow down the cylinder,while it was running ..the noise went away when you got to that cylinder cause there was no power stroke?.might try that

 

Yea they don't worsen too much. I've had that noise since I bought my car 40,000 miles ago and I've beat on it and increased power output and still has yet to get any worse.

That's one way to find the bad cylinder. Just don't pull the wires while it's running unless you want to get shocked.

 

use rubber insulated gloves.. the good rated ones.. 10k volts or so..?

 

Get it warm where it does that, then park somewhere dark dark dark and pop the hood.

 

definitelly exhaust manifold gasket...I had the same problem....figure out which one is louder and cahnge it or just do both at the same time

Make sure you use a lot of PB blaster when taking nuts out....ITs really hard to drill them out if you break the studs...(because there isnt much room under the hood)

 

or the easy way would just be to turn the car off then take the plug wire off then start the car