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Q & A: High Idle

I have set the ignition pretty well but here is the problem. The engine rebuild included a new VP-11 APT cam, I had to overbore to .060, and a ported and polished standard late head, opening up the ports a good deal. I have needed ether to start it initially when cold so far. Once warm it runs way too fast, about 2100 rpm at idle with the choke off and throttle screws backed out full. If I lift a carb (standard HIFs) piston it dies out nearly all the way. That tells me the carbs are too lean. Looking in the throat of the carbs the jets are maybe 1/16ths or less down from the shoulder in the carb intake. If I richen the carbs, it should speed up more. I'm guessing that with the increased volume flowing through the vacuum in the intake is lifting the carb pistons too much and drawing more fuel. It seems to me that the only solution is to change needles to something that allows less fuel at idle. Is my logic wrong?

Rev the engine right up to 4000 or so and set the timing at 32 BTDC at max advance with the vacuum disconnected. By 4000 the distributor has usually opened all the way. Then let it idle down and re-connect the vacuum -- if you check it again at ... read more