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Discussion Starter · #1 ·
I have a 67 ss with a 396/375 hp. engine. Picked up a nice holley 650cfm double pumper(had a 750 double pumper on and had no problem, just thought I'd make a change) When I hold the accelerator at a steady speed of anywhere from 40mph to 55mph, I notice a slight surging rather then a steady constant movement-more like a pick up and back off of speed but pretty slight. What may this be(float problem/mixture problem) and any suggestions on the fix. I can always go back to the 750cfm but I'd like to correct this one if possible. Thanks all!
 

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66 El Camino 57 Chevy pickup 2004 Tahoe
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if you have a vacuum advance try a cruise without it hooked up. If that doesn't make any difference try two sizes richer jet in the primaries. double check the Holley site with the list number to see what size jets are supposed to be in it.

how does it idle? any signs of vacuum leaks? are the idle mix screws about 3/4 turn out from seated?
 

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Premium Member
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Discussion Starter · #3 ·
I have no vacuum advance hooked up/ the idle fluctuates from 750rpm to 800rpm. I will check the set screws and check with holley on the jet size. Thanks for the help-you've given me a direction to head in!
 
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