94 Camaro Z28 LT1 350cu/in, loses power during acceleration between 1500 & 3000RPM. Accompanied by loud tapping noise which icreases in tempo with the rpm's. tapping continues at idle and symptoms worsen as engine heats up. Tapping noise sound as though coming from the right head. No bent pushrods, reset valve lash, no broken valve springs. Engine compression seems good. Could it be collapsed lifters?
I added a heavier weight oil to try and determine if the pressure change would affect the tapping or performance; however my starter started sticking meshed with the flexplate teeth. I just got the shims but haven't installed them yet.

 

how did you "set the valve lash" ?

without actually hearing it, you could have rod knock. Or, maybe you have aftermarket rockers and they are simply loud???

How do you know that none of the springs are broken? Did you remove and inspect the springs? May we also assume that you removed the intake manifold in order to inspect the lifters and push rods? Or, did you loosen each rocker and pulled the rods up?

 

^^^ agree is it knocking or ticking?

 

If i had to choose between a knocking or ticking i would choose a ticking noise. i didn't remove the springs, only looked at them. the rockers are stock...I did remove the entire intake manifold, valve cover, rocker arms pushrods, & lifter retainers within valley between the heads. I set the lash by moving each cylinder to TDC and tightening the rocker arm nuts til the very point where the pushrods would not spin by hand, then giving them another 3/4 turn to set the preload as stated in the Haynes manual.

 

Forgot to list the lifters themselves as having also been removed. I checked the lifter wheels for excessive play and obvious damage, and i rolled the pushrods across a sheet of glass, flat glass of course.

 

then if it's not a knocking, have you checked for exhaust leaks by the headers? Some folks choose to not use dead soft aluminum gaskets such as Percy's when installing headers and they end up with leaks later on down the road.

 

I'll try replacing the gaskets before i get the starter reinstalled..

Any other suggestions?

 

Curious, what is your oil pressure?

 

This here could be the problem. This is not a good way to get them all even. The amount of force that will stop each pushrod from spinning can very greatly, and give you different settings on each.

Loosen each back up. on the TDC compression stroke of each cylinder, tighten the rocker untill there is 0 lash (no up and down movement) You should still be able to spin the push rod. Now tighten 3/4 of a turn. This should put the lifter piston in the middle of its travel, right where you want it.

Massey

 

Ok i'll have to give that a shot as soon as i get the opportunity to get the starter reistalled. Hopefully this week. I did add a heavy oil to see if that'll improve the performance, hoping to zero in on the lifters as the culprit(collapsing).