Re: 1956 Clipper Hot Rod

Posted by BH On 2009/10/21 7:45:06

Disconnecting a plug wire is a good old trick to ID a cylinder that's not firing (provided your careful in handling the wires), but that doesn't really tell you whether the localized condition is due to a problem with a plug or lack of compression. The latter can involve either rings or valves - hence the need to run both a dry, then a wet test.

Should be easy enough for you to remove the plugs on the affect cylinders and test with a voltmeter. If all else fails swap with a plug from a cylinder that does fire and see if the miss follows. Of course, I'm assuming your mechanic checked for spark at the end of the wires on the affected cylinders and found no problem.

Given your description, at this point, I doubt if it's anything more serious than valves or rings - like pistons. Still, I'd be curious to see compression test figures (both wet and dry) cold, then fully warmed (where it seems to overcome the misfire).

If the test results point to valves, it is not that difficult to pull a cylinder head and inspect things. Whether you fix only the affected valves (which a good mechanic can handle) or do a full refit for unleaded fuels (which would require a competent machine shop) depends on your budget.

Unless there is some serious wear, you could overhaul the pump and carbs yourself. I suspect kits would go about $50 a piece these days.