Low Compression

[JDRiv]

My '63 401 has low compression in two adjacent cylinders on the right bank. I'm hoping a new head gasket will fix the problem. Anyone have advice on getting that done...or a recommendation for a good shop in the Denver area?

Thanks!

JD

[Guest rsteere]

JD.

How low is low? Did you try a couple of squirts of oil and retest to see if it comes up?

Randy

[1965rivgs]

Hi Jeff,

I would do a leak down test to gain a little more info. It is true a head gasket which is leaking compression between adjacent cylinders would produce low compression in both but this would be very unusual in a nailhead. I would confirm the diagnosis before teardown and eliminate the possibility you have a bad intake valve or just two cylinders which are adjacent and have a problem peculiar to each.

Tom Mooney

[lrlforfun]

OK Riviera People: I agree on the leak down test. Remove the rocker shaft so all the valves are in the closed position. Inject air in to the spark plug hole. Listen for the air sound. if it comes out the carb it could be the intake valve, if it comes out the exhaust, an exhaust valve and if it goes into the crankcase, rings or piston or worse.

If the exhaust isn't tight you might not be able to hear the air coming out. Also, you can do a pressure test on the radiator. Remove the plugs and get some pressure going with a pressure tester and listen and watch for possible for air/water leakage.

I never get lucky. Old engines usually need the full meal deal so realistically plan on that option. A 401 can easily be 5K with r&r. Good Luck, Mitch.