Still could be valve lash etc, not allowing proper flow etc and maybe one valve is slapping the top of the piston, just my opinion.
I'm with you here except this issue didn't slowly occur, it was an immediate results of the engine running in extreme conditions.
Whatever is wrong was caused by a really hot engine, running really thin/hot oil. I'm not saying the valve didn't come out out of spec though..
Got to agree with SHOYAY : valve lash adjustment.
--- what Shim was that? A valve train shim?
As far as compression: might not be the best conditions for that test. cold, engine should be warm etc etc. You could always do another test later in better conditions --
the low cylinders are on the rear bank?
One of the exhaust shims for cylinder #2 had ejected ( without any damage) and the car collected a carbon deposit in between the valve and the seat. I remedied this by putting the shim back in and running Marvel Mystery Oil through the cylinder.
And about the test, your absolutely right, I was so caught up with the spark plug boot being stuck I forgot the engine needed to be at operating temps, I'm run another test tomorrow for more reliable results..
My 90 had a rotten tap I could never track. It's Daniel's (SHOhopefull) now. It sounded similar to that but maybe not as loud or severe. I pulled the valve covers, and found a pitted shim and cam lobe on the front left cylinder (if you're facing the car). I swapped in a new cam and shim (BTW all valves were in spec), put it back together, and it still tapped!
I drove over 3k miles with the engine doing that, and it still does it! If it were a bearing, it should have killed the motor long ago. The only thing left I could think of was a sticky valve because it was concentrated to that 1 cylinder.
When I was under the rear valve cover I gave all the shims/lobes a visual inspection , and while not a definite way to say they are in spec , there was no visual wear of any kind.
So no chances of it being a broken valve spring then?
I agree with SHOWGUN, it's absolutely possible and after giving it thought it could be a very plausible explanation.
Giving that the knock will not immediately start with a cold engine start but will become obvious after idling about 45 seconds to 1 minute I was assume it's a part that is constantly moving and fatigued from the overheating and becomes stressed once it heats up.
What I'm saying is that a valve springs is a very real possibly.
I will have to secure another 5mm hex on a 3/8" adapter tomorrow morning but hopefully I'll have a decent amount of time to take the cover off and inspect everything..
Expect ore accurate comp test results as well as some pictures later on in the day tomorrow.
Thanks for all the ideas,
Josh
EDIT: Sorry I didn't realize you guys had posted before I put up m reply..
If you want that car to run right, you're going to have to have that head off, inspected and rebuilt, if necessary.
Think about what a spit shim means...
It means the shim lost contact with the cam lobe.
That means the valve was stuck open. Either it's bent, or there was enough carbon built up on the stem, that it got jammed up.
You got it moving again, but it was run for a while with that valve partially open. That means the combustion process was not contained to the cylinder, but also to the runner that valve was supposed to seal (edit: which includes the valve stem and seal...which is probably blown out).
In my case, it was the number one(a) exhaust valve. I never took the head off of that engine, but I can almost guarantee that exhaust valve and seat were toast.
Or what you could be hearing is the valve getting stuck and bouncing the shim off of the cam lobe. Either way, if you're as determined as you say are, order up some head gaskets and have confidence the head is OK by having it rebuilt.
I follow you, and from what I can visualize is that while the valve assembly was moving again it was already burnt up and all it took was the the right conditions (hot engine,thin oil, 4500rpm pass) to completely destroy it. Am I on the right path in this though process?
As I said I'll have the rear cover off tomorrow so I can inspect it.
Can I get away with just having the rear head rebuilt? Wouldn't be any reason in spending a notable amount of money fixing something that isn't broke, correct?
