Evaluating valve adjustment time by sound

[Bob Kontak]

Originally Posted by Otter74

and the top end was redone in 2013 because somehow the exhaust-side valve guides were missed the first time.

On a side note Engine Builders Supply farmed my heads out in the late 90's. The rebuilt heads were sent back with the exhaust valve seals in a separate bag. I asked what the heck? The said you don't need them was the response.

I never dug into it any deeper. Not sure why.

[T77911S]

not sure how you miss the exhaust valve guides, they are the ones that go bad.

I will go back to my statement of valves get tighter with mileage to help you answer your own questions.

if you have one that gets noticeably louder over time then perhaps you have another issue.
you could have a plugged oil hole in the spray bar and you are wearing out the cam/rocker thus increasing the gap for example. I have seen this happen first hand.

a shaft off center wont do it unless the shaft is worn and has moved or one end has come out. shafts have come out and the rocker fallen off. again, nothing to do with a valve adjustment but a mechanical failure. also seen this happen.

did a machine shop that knows how to do Porsche heads do the guides?

if you are hearing what you think Is a rocker here is what I would do.
go in and do a valve adjustment. adjust them on the snug side. make sure they are done right.
after doing them, spin the motor over a few times then go back and check them again.
check the head studs. just put a wrench on them and make sure none are broken.
inspect the rocker shafts. make sure they are at least consistently in the same place. you could even put a wrench on them and make sure they do not turn. if they turn, they can move.
inspect the cam lobes and rocker faces for wear.
inspect the spray bar holes for anything that could be plugging them. mainly the ones that face up.
button it back up and run it again.

my 77 was noisy after valve adjustments. I also noticed that after adjusting them the first time they may not be the same when going thru them again.
I just always suspected bad guides and they may be moving around.


one last thing.
did the pistons get replaced?
I have been told:
JE pistons can cause piston slap due to the fact that they do not have the offset that Porsche pistons have.

[Otter74]

Yeah, it does seem odd that the exhaust guides were skipped the first time, but that's what happened. I've got records on the rebuilds at home, but this is what the PO (who was on this forum - the car was originally advertised here) wrote:

"Original rebuild was done by an Atlanta area shop that went through a change of ownership in the middle of the rebuild. All was good with it, except valve guides on the exhaust side did not get done. That resulted in bad smoke on deceleration last year. I did the top end myself, except for sending out the heads to Motowerks Racing in Cumming GA. They did the assembly but sent the actual machine work out. The new heads and cams really woke the engine up."

I don't remember whether it has Porsche pistons or not, but I do have that information at home. The PO had the car for 15 years so I've got records back to about 2001.

I do not have an experienced enough ear to say that there might be a misaligned rocker - that was the opinion of the mechanic in Nashville, and he did not even say that he thought that *was* the case, merely that it was a possibility. It was an informal conversation. He did show he how it could cause a little more noise, but I don't remember the explanation.

Thanks for the suggestion below. I will do that when I do take the covers off and check the valves, but I am inclined to do that either this winter or at the next oil change after this one. I'd be be more worried if they were tight!

Originally Posted by T77911S

not sure how you miss the exhaust valve guides, they are the ones that go bad.

I will go back to my statement of valves get tighter with mileage to help you answer your own questions.

if you have one that gets noticeably louder over time then perhaps you have another issue.
you could have a plugged oil hole in the spray bar and you are wearing out the cam/rocker thus increasing the gap for example. I have seen this happen first hand.

a shaft off center wont do it unless the shaft is worn and has moved or one end has come out. shafts have come out and the rocker fallen off. again, nothing to do with a valve adjustment but a mechanical failure. also seen this happen.

did a machine shop that knows how to do Porsche heads do the guides?

if you are hearing what you think Is a rocker here is what I would do.
go in and do a valve adjustment. adjust them on the snug side. make sure they are done right.
after doing them, spin the motor over a few times then go back and check them again.
check the head studs. just put a wrench on them and make sure none are broken.
inspect the rocker shafts. make sure they are at least consistently in the same place. you could even put a wrench on them and make sure they do not turn. if they turn, they can move.
inspect the cam lobes and rocker faces for wear.
inspect the spray bar holes for anything that could be plugging them. mainly the ones that face up.
button it back up and run it again.

my 77 was noisy after valve adjustments. I also noticed that after adjusting them the first time they may not be the same when going thru them again.
I just always suspected bad guides and they may be moving around.


one last thing.
did the pistons get replaced?
I have been told:
JE pistons can cause piston slap due to the fact that they do not have the offset that Porsche pistons have.