I have a 406 sb in my 66 chevelle. It has 373 gears and posi. The engine has fully worked heads and a 292 cam with 512 lift intake and exhaust and 244 @ 50 duration. The car is slighty surging when cruising around. It is almost enought to make me hit the gas due to the surge. If you floor it, it will take off and run like hell. I'm suspecting in the 1st and 2nd gear I'm loping on the cam and that is what is causing this. If anyone knows or has had this problem let me hear your solutions.

kevin

At what RPM range is it surging? Could it possibly be in the distributor? I've seen an engine surge at low engine speeds due to the mech advance in the distributor. The springs were too light. Just a thought.

Kevin, you didn't mention anything about fuel delivery - what size/type of carburator are you using and if it's a Holley, what size jets are you running on the primary side?

Your engine may want more gas at part throttle, which means it COULD be running a little lean on the primary throttle side - Holleys will behave that way under partial throttle if they are too lean. Once you floor it, the secondary's fly open and clear up any previous lean condition. Maybe try jetting up in increments of two and see if that clears up the problem. Also, check your power valve (on the primary side) to see that it is the right sized power valve - if so equipped. Hope you find the cure!

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70' Malibu - 383 'Dental Gas' Inhaling Stroker! Gold Member #39
Chevellz Alwayz!

sounds like your a little lean at part throttle. quadrajets and the carter afb act the same way as the holley.

Sorry I'm using a stock 750 double pumper with mechanical secondaries. I don't know what size the jets are. At first we had the floats to high and kept fowling out the plugs, it surged then as well. As for rpm range I don't have the tack hooked up yet, usually when I drive it I'm moving it to shops to have work done or testing he adjustments I've made to the motor.

thanks kevin

Kevin, I would definitely pull the front bowl and see what size jets you are using AND find out if your power valve is blown and what size it is...let us know what you find. Good luck!

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70' Malibu - 383 'Dental Gas' Inhaling Stroker! Gold Member #39
Chevellz Alwayz!

ive had the vacuum advance also cause that.i just left it un hoked and it cured the problem. just a thought.