Valve adjustment problems and compression test results

[Inf]

I was adjusting my valves today for the first time (cold initially so I can get it down, then warm later).

Adjusting the exhaust valves was easy.

The problem I ran into was with the intake valves. On most(all except maybe 2) of them, the adjustment nut was already so close to the lock nut that even when I turned it in the correct direction until it would turn no more, the clearance was still too small by 4-6 thousanths.

This head is original and still has the bronze(?) valve seats as far as I know. I've been told they get 'beaten' into the head after many miles, especially without leaded fuel, could this be related to my problem?

On a related note, I ran a dry compression test (cold motor)finally yesterday and it went something like this :

Cylinder--pressure

1--180

2--175

3--170

4--155

5--145

6--125

doing a 'wet test' on the low cylinders did not increase the pressure at all. I'm told this shows a decreased likelyhood in low compression because of worn rings/bore and more likely due to head issues.

I should also point out that the front cylinders allowed me to get closer to the intake valve spec on adjustment, with 1 being right on, down to 6 which at max adjustment was only about .002 clearance.

I have a rebuilt e88 head sitting on my workbench(picture in my gallery, btw) that I will probably have a shop move the cam/cam towers/rockers over to from my current head. (or is this a bad idea?)

Any advice you engine guys could give me would be helpful.

[landmizzle]

Hi INF,

You should redo your compression check with the engine up to running temperature before you try to determine the state of your motor. That said, you do have some large variance in the readings you supplied. The "wet" test you described does tend to tell you if your low compression readings are a result of worn rings or issues in the head (valves, seats, etc), so you're going in the right direction to diagnose this yourself.

With what you discribed about the lack of adjustability on the valves, I would tend to agree with you that your valves my have receeded but, I'm by no means an expert in this area.

Hope this helps.

Best Regards,

Landmizzle '72 240z

[SER240Z]

Sorry off topic, but what do you mean by a "wet test"? Thanks, just curious.

Scott

[MikeW]

Originally posted by SER240Z

Sorry off topic, but what do you mean by a "wet test"? Thanks, just curious.

You pour some oil in each cylinder through the spark plug hole before doing the compression test. If doing this raises the numbers that indicates that some of the leakage was occurring past the rings. If it doesn't change the numbers then it's more likely a valve issue.

[Inf]

Thanks for the replies, I am in the process of pulling the head right now anyway. I figure I have this head sitting here with all the hard parts done already, I may as well have it finished up.

[Ed]

While you have the head off inspect the cylinder walls. Look for scratches that could indicate a broken ring. Also unless you plan on removing the front engine cover make sure you properly secure the timing chain tensioner. Good luck.