MG Car Repair: Intake manifold, head gasket leak, combustion chamber

Question
I added shims under the intake side of the washers to give better contact on the gasket. No change it still leaks. Still runs rough on idle and 1500 rpm. Adjusted all the valves to .013", set the timing and did a compression test. No1@ 145,2@ 135,3@ 140,4@ 145psi. I did the leak down test and heard air from cyl #3 when 2 was under pressure, and air from 2&4 when 3 was under pressure. Not alot but noticable. What does this tell me? That some of the valves are not sealing as tight as they should. The compression test tells me the gasket is ok. Correct? Thanks

Answer
Allen, an intake DON'T leak with a surfaced manifold and proper bolt down pressure unless there is a crack. A compression test does NOT test a leaking head gasket unless it was completely blown out. How much compressed air pressure did you apply to the #2 cylinder? If you had leakage from #3 when 2 was under pressure you have a head gasket leak not a valve leak. (if you did it the way I told you) If you have leakage into 2 and 4 when 3 was pressurized you have a head gasket leak NOT valve leakage.

Get the spark plug hole adapter and put each piston at TDC of the compression stroke and put it in 4th gear and hand brake on and put compressed air on the combustion chamber with all the spark plugs out and do the combustion chamber pressure test as I told you and if ANY air leaks into the combustion chamber next to the one being tested correct the head gasket.

Howard