I have a slant 6 in my 63 plymouth and it runs really good cold but as it warms up it starts to drop rpms at idle and will stall even in park at idle. When cold it idles at 1100rpms to 1300rpms in park. In drive it idles at 700rpms. Once it gets hot it will backfire out the carb whenever it's given gas. The carb on it is a rochester 2bbl. If anyone knows what the problem could be please let me know. Thanks

Have you checked the valve lash adjustment?
Tight valve lash clearance gets even tighter, as the engine gets hot.
DD

Have not checked. What should they be set at?

.010 for the intake and .020 for the exhaust is the factory valve lash setting.

Brian

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63 Plymouth Valiant Wagon

Thanks. Also i dont think the valve that controls the exaust
to the intake manifold is working at all. Do you think this is part of the problem?

If the heat riser valve is diverting exhaust to the underside of the intake manifold even when the engine is hot, then yes that could be part of the problem.

Just to be clear, that .010" intake and .020" exhaust lash should be set when the engine is hot.

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Somehow I ended up owning three 1964 slant six A-bodies. I race one of them.
Escape Velocity Racing