Hi, I have a rebuilt 8ba that is not running After about 20-25minuster of driving, the engine starts to missfire and goes worse and worse. After about 25minutes it will only go at idle for a while before it dies. After it cooled of a litle it will go perfect again for 20-25 minutes. The engine is a 8ba with Edelbrock cylinder heads, 77b camshaft, two new stromberg 97 and a new Mallroy dubble point distributor. -I have checked the ignition timing and it is ok. -The ignition coil is also ok and is not warm -I have checked the pointers in the distributor (tried 0,020 to 0,018; 0,45-0,5mm) -The carbs is new, english built and adjusted Does any one have any suggestions where to continue? Im out of ideas..
I would still suspect the coil or possibly, the condensor? Have you checked the fuel pump pressure when it is acting up? If all that is OK, then maybe you are getting water in the combustion chambers when it gets up to operating temp. Cracks? Seeping head gaskets? Ray
I bought a brand new motorcycle to take camping. After 5 miles, it would quit. Once it cooled off, another 5 miles and it would quit again. I took it back to the dealers under warranty and it did the same thing. I finally told them to replace the coil or give me another motorcycle. They replaced the coil and I never had a problem again. I've had bad condensors and the only symptom was missing, but it never stopped running.
If your ignition checks out OK, check the valve lash. Could be set a tad too tight and some valves are not sealing to their seats when the engine heats up. Problem goes away when it cools again. Happened on a Studebaker I had with a fresh rebuild. Suspected the problem was in the ignition system and replaced a few parts before we discovered the tight valve lash issue.
I have a 36 Ford Tudor and the same thing happened to me. It was the coil, try a new one I think your problem will be solved.
X2 My '38 had the same problem. Also had a new Mallory ignition. Changed the condenser...................bye bye problem. Frank
The coil doesn't have to be physically hot in order to fail. Swap in another and see what it does. It could possibly be the condensor, but most likely the coil. Do you have a ballast resistor so the points aren't getting fried? Just something you should have regardless. I would look at them anyway. I always carried a spare coil with me, also saved the points, condensor, rotor and cap when I did a tune up. You KNOW they were working and are invaluable if you get stuck somewhere. Bob
I suspecter the coil aswell at first. So i changed the coil. The coil gets 12v and is supposed to run without a resistor. The pointers does not need to be cleaned after running. I had this problem at first, so i had to change the capasitator (condenser?) to a bigger one. I was told that the original cap. on the Mallroys is not good enough and will often fail/break down. I have been thinking of the valve lash as well! Might be a litle tight. but i would like to try all the easy fixes at first..laysy as i am . I have not checked the dwell yet as i do not have a dwell meter.
I rebuilt a 153 cu in 4 cyl chevy II, used the original coil and dist. The engine had the same symptoms as described. After trying many things I finally found it was the small wire that goes from the coil to the dist. to be the problem. When the wire was warm/hot from the engine heat it would sag causing the broken wire inside the plastic sheathing to separate slightly causing the engine to miss fire when the wire cooled it would contract and work just fine. It took about a month of trial and error to locate.
Went out and started upp now and after the engine had reached 160F in temperature i had it idling for half an hour. gave it some throtle now and then during during the run. No problems at all the engine runned very nice. The only difference from driving is that the alternator is not charging at idle. The alternator comes from a ZZR1100 and i have no external voltageregulator. It is charging about 14volts or sligtly higer but not over 14,5volt. Could it be that i have a over voltage at the coil? it is a long shot but.. will try to install a voltageregulator to morrow and see if it gets better. At least i now think that the valve adjustment is ok.
Kamikazie, I still think that your voltage is too high getting to the condenser. Even though you have a coil with an internal ballast resistor you may want to try running an external ballast resistor in the ingnition wire going to the coil. Is the mallory a new one as Speedway sells? If so, they usually are not very good out of the box and have to be set on a distributor machine. I have had two of them that needed the advance curve reset (GMCBubba did mine).
Yes, it is a new Mallroy dubble point distributor. I have bought it from a dealer in here in Sweden. Ill try to set up the distributor in a machine during next week. I will measure the voltage at the condenser later today. i have a resistor on the shelf, ill try to install that one aswell.
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