Maybe the valves are too tight causing low compression. Any work done in that area. I’d perform a leak down test.
Did you check your comp tester against another? I seem to recall something about this not too long ago. Or not...? I had a comp gauge go south on me and thought I blew the motor. And to really make a grown man almost cry the one I borrowed was broke too! Just a thought.
Lots of great ideas to try. Going to start with another compression test. Pull the plugs and watch the valves for movement. The shop had the oil pan off when they installed the clutch. Front cover was off and said the teeth were good , but may not have checked the timing marks.
Ddrraattiitt those wandering RRR's !!!! What to do about them !!?? I'd get out my handy vacuum gauge and see if it also is wandering or holding steady. Get a can of Valvoline Starting Fluid ( safer on valves than other brands ) and spray around the carb base and perimeter of intake manifold . If RRR's rise repair whatever vacuum leak you may have . If no rise in RRRs then use another carburator . If still no results ditch the electronic distributor and go with points distributor everyone carries one with them on a serious road trip when running electronic . distributor . Check your distributor wire voltage is it compatible with your electronic unit ? You don't just slap these things on and fly you know its all got to sync together and I would start over with factory equipment for domestic application not for marine or race or whatever else . Troubleshoot with stock original parts from the showroom floor it will make your troubleshooting so much more understandable . All diagnosis is a process and get a vacuum gauge and learn how to tune your motor to it when using stock camshafts . Good luck and any questions you can conversation it to me
6 vole system may not turn it fast enough to show a high compression reading. It does start and run but not very long. You changed the ignition and carburetor that had no improvement. Sounds like fuel, vacuum or exhaust problem to me.
While the compression is low, you have said that the engine runs fine for a while then goes into a poor running mode. Compression doesn't change, so you are looking for a variable that can/does change. While you should fix the compression later, I would only be searching for something that changes after the engine is running. Could be lack of fuel because of poor venting, carb problem like a bad float, on and on...........or an electrical issue like a poor ground or cracked dist cap etc..........but if the engine runs well initially I would say that the low compression probably isn't the issue.
It's likely a distributor problem, check the fly weight springs under the dist plate, some times they break, check all your vaccum hoses and hard lines for leaks, sounds like the mechanical advance puts the dist in correct "time" ocasionally. Also check your vaccum wiper motors, they should be all the way off and no leaks in the rubber hoses up to them. Check the carburator for mounting gasket vaccum leaks and any open or rotten rubber plugs. If you slowly choke off the carb while running, if the RPM rises before engine dies, there is a vaccum leak. Also replace the coil qith one that's known to work, sometimes as coil temp goes up it fails .
Well heres the finally. I went and pulled all of the plugs and did a compreesion test. All 100- 110#. Checked all of plug wiring. Just fine. Checked for any vaccum leaks. None. Started it up and let it run at a higher idle......Big backfire...Engine running fine. Backed it out and took a 20 mile drive and back home. I have no idea !!! This problem has had me looking on and off for months. One backfire and it is solved. ??? Go figure ! Thanks For all of the suggestions and help. Terry
Wow! Maybe you backfired some “Schmutz” out of the carb! I was starting to think it was coil related….
I have had it out on the road a few times getting use to running again. Runs pretty good in 35 mph traffic. Every once in a while it will backfire and start missing again for a while. Thinking it may have a sticky valve. Got it up into the 50's on and open stretch yesterday. May need a little more advance in the dist. Kind of falls on it's face when give more throttle.
Ha-haaa the engine got tired of you trying to figure out what the problem was... then fixed it'self! (I'm always suspicious of a machine that heals though...)
I'll throw my guess in here. You didn't mention if the electronic ignition was installed in the same distributor as the points. If so , I would guess you have a problem with the ground wire or short in the primary feed when the plate moves. I'm guessing you have the vacuum advance hooked up . Is it working? When the advance kicks in and out , you loose ground or primary feed. Check it out.
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