Got my '41 flathead running, but it still has some missing and backfire. I have no idea as to how long it has been sitting or any of its history. I figure the problem is sticking valves, since I have an all new ignition system with electronic dist. With all of the snow and cold weather I will chose to leave it in the heated shop. I would like to add something to the oil and run it for awhile and then let it sit then run and let sit. What would be the best product to add to the oil to help with the sticking valves ?
Do a compression test. Obviously the cylinder(s) with zero compression has the stuck valve. I like to do it with the engine warm. With the plugs out you can see whether or not the valves are moving. Any that aren't moving can usually be freed up by carefully tapping or pushing them down thru the spark plug hole. Make sure the cam lobe is down before applying any force to the valve. I just unstuck a couple of intake valves on a '40 that had been left sitting for too many years. It takes some time and patience to get them unstuck so they stay unstuck, but the one I just did runs very nicely now. By the way, a combination of WD-40 and Marvel Mystery Oil worked for me in getting them unstuck and staying that way. Good luck.
It could have burned valves, too. Last year I had to grind the valves and seats on an 8BA that had sat in a barn for 30 years. It also had 3 stuck valves to deal with and plenty of crud and corrosion to clean up. Glad to see you got it running.
I'd agree 100% that a proper compression test is step one. By proper, I mean remove all the plugs, prop the throttle wide open, make sure the choke is wide open and let the compression hit on the gauge five times on each cylinder. Write down the compression as you go and then study the results.
Digging this back up for hopeful help on my situation. I have a misfire, quick summary of what I have done. I have run my wires in the old style "conduit tubes" or looms that ford used. I have checked plugs, plug ohms, plug function, wires, wire ohms, wire function, cap (for cracks), fuel system is not the problem, its dialed in just about perfect. Hot and cold compression checks good. Swapped another set of different brand plugs, with no success. It's a fresh engine with 300 miles on it. Running Mallory Unilite dizzy backed with a MSD 6AL box. I'm leaning toward the wires in that loom being an issue. I can't see in there, but I feel like that's where it's happening. I have run it with the lights off in the shop and can't see anything arc. I've only got a misfire on one side, and I think 2 of the holes. Maybe valve adjustment too?
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