Of the few dozen times I have had my XJ6 running it sounded normal, last time I noted what seemed like some valve tick on the intake side and thought perhaps I'd look into a stakedown kit later.

Today I started it up and it had a much louder tapping. Seemed like the #6 intake valve from listening. I pulled the valve cover and that particular valve has 0.024" of clearance? Car has 140k miles

This seems pretty far from the 0.012-0.014 spec. The others all seem to be within this. Why would one be so far out? Lifter or valve itself sticking?

Is my only option to pull the cam and see what is doing? Should I maybe try "bopping" the lifter down to see if that breaks it loose?

 

Yeah nevermind, no surprise such a big gap on only one cylinder is indicative of a valve problem. Zero compression on #6. 150 psi on #5.

I'm completely baffled that it ran totally fine last time it was used, nothing has happened since then, and now I've got a bent valve, broken spring, or dropped seat? Should probably close this thread and make a new one looking into why my intake valve suddenly stays 0.010" open.

 

Not good, for sure. The valve is not sealing for one reason or another.


Kudos on the compression test. A great diagnostic path.


Carl

 

I had similar after an engine rebuild. Valve must have been a bit lazy coming back up and was kissed by the piston which bent it slightly. Only cure is to have the head off and replace the valve.

 

Yeah I'm thinking it may be stuck down from carbon build-up but don't want to take the chance seeing if it'll run itself out with the risk of piston contact. Hell the tapping could have been piston contact rather than from the excessive clearance. Either way it seems the head is coming off.

The intake looks like a pain in the butt to get off. Is it common to pull the head with it attached on the SIII? Looks like I can pull the exhaust, oil feeders, a few hoses, then disconnect the cam sprockets and itll come off in one piece.

 

You pull the head off with the inlet manifold still attached, but normally remove the exhaust manifolds. At least that's what I did !