Triumph Repair: low compression, blown head gasket, compression stroke

Question
Thanks again for your insiteful previous replies. Here,s the final low down.  The compression tester I previously used was no good. I borrowed it from a parts store. I just baught a new one and ran the tests again. cyl's 1-4 resectfully, 145 ,60 ,145 ,145psi. Do you have any suggestions before I pull the head off. The car had been sitting for 3 years in a hanger. Previous owner new nothing of this problem. I believe this to be true. Thats not to say it wasn't like that when he had it, he just didn't know. Thanks Pat

Answer
Hi Pat,

I would not pull the head until I put #2 at TDC of the compression stroke and check valve clearance and then put a fitting in the plug hole and connect line air pressure to the cylinder. (in 4th gear and hand brake on) then listen in the carburetor and at the tail pipe for any hissing. Then run a wet and dry compression test on that cylinder to see that it is a valve, Rings or blown head gasket.

I have prematurely pulled a head just to find that the valves and head gasket were good and it turned out to be a broken ring.

Even though you have found the problem to be #2 for sure check the valve clearance first and run a wet test by putting several squirts of engine oil in the plug hole and run a second compression test and if the pressure don't change much and the valve clearance was correct (not too tight and not an excess clearance) you can be reasonably sure it is a burned valve. If the wet test brings the pressure up almost to the good, then it is a ring problem.

Howard