Rough idle

jerdan

jerdan

Member
I have a stock 239 v/8 that idles rough. If I pull the cake out a little it smooths out. I have tried adjusting the mixture screws. It does't seem to make any difference. I can screw one all the way in and it still runs. If I turn the other one all the way in it will die. When I step on the throttle it hesitates. Any help is appreciated.
 
It sounds like the carb has some issues. Is it a Holley 94 type? It is probably running over rich due to one of many possible causes. Holleys running rich have been discussed on there many times.

Mart.
 
I think my approach would be to rebuild the carb. Do you have a spare carb that you could throw on?
 
They can get internal leaks from a bad or ill fitting power valve. If the idle screws are all the way in on either side, it's a good bet that the fuel is coming from somewhere else. Late type power valves don't always fit the old housings well but this can be remedied. Ford Barn member CharlieNY has a fix and is a good source of parts or for complete overhaul.
 
Stick valves can cause ruff idle. Drizzle MMO down the carb while
engine is running and a pint in the gas tank. Drive about 25
miles and if that's the problem it should go away. G.M.
 
Vacuum leak can cause rough idle too. Check your distributer connections and wiper hose and fittings. It is often that for me. To me a perfectly idling flathead V8 is a huge part of the draw. Nothing else idles like that when all is in order.
 
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