Greetings. I have a '71 Dart Swinger with a slanty. The car has 34,000 original miles, practically a brand new car. The problem I have is that the engine is missing something terrible. When it's a cold start it seems to run fine, but as it warms up it starts missing and gets progressively worse until it quits running, although it seems to run fine when driving. Quite a few things have been replaced. When I got the car I upgraded to a new distributor with Pertronix "points" and a Flamethrower II coil. New plugs, wires, cap. The 1920 carb that was on it leaked, therefore changed the carb. None of these things have changed the idling. I have adjusted the timing to 5 btdc, and adjusted carb idle needle. It seems to be running really rich, but when I try to lean it out it dies. I have plugged up every vacuum port that I could find to see if I had a vac line leaking but that didn't isolate the problem. Does anyone have an idea what could be the problem? Thanks!

Have you checked the valve lash?
DD

Yep. Tight valves can be okay cold, but idle terribly when warm. I bought a car where someone confused the lash numbers and set the exhaust tight and the intake loose. You want .010" on the intake and .020" on the exhaust, hot.

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Joshua

See valve adjustment procedure here and tune-up parts and technique suggestions in this thread. You may also be dealing with a vacuum leak (manifold-to-head gasket, for example) that opens up when it gets hot.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Cool, thanks for the info, I appreciate it. I will make that my next step in my troubleshooting.

After checking with carb cleaner, I found that 3 & 4 cyls had a big leak at the intake. I replaced the manifold gasket with a Remflex. That solved the problem. It still runs a bit rich to me, so a little tuning should hopefully finish it up. Thanks for all the suggestions and help!

Was it a car or a truck?

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~Nic

1967 Valiant.

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Joshua