Thread: mid to high rpm stumble-no power

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on top of that ram i would look at the air bleeds blow air thru them to make sure there is no junk in there i think i would go up on jets and go back to a 3.5 power valve the back of that carb is just a plate no jets ? or power valve ? a double pumper is what you need

The carb is a new 4160 with a plate (instructions said equal to 75 jets) and checked the air bleeds and all is clear. I put the 72 jets back in with the 35 power valve and the car ran pretty good but sputtering on the top end still. So I changed the mechanical advance to the red 28 degree bushing and set the intial to 12 degrees. Car started and ran good as usual just cruising around. Now when I mash the throttle the sputtering and popping through exhaust happens much earlier in the rpm range. Is this a symptom of the engine not getting enough fuel like was mentioned? I am going to try a buddies 750 double pumper or race demon carb to see if more fuel helps. Thanks for your help guys.

Update, so I borrowed a friends 825 race demon and currently have it tuned with 95 main jets, 45 power valve, 99 secondary jets (started with 72p and 91s, then 80,90 and 95 primary with 99 secondary)with 45 squirters primary and secondary. Each increase in primary jet size helped the car pull harder) Car has an off idle hesitation under load(need bigger squirter?) but pulls really well until you open up the secondaries then I get the same condition of popping out exhaust/cutting out and surging. If you keep the secondaries open it surges and tries to smooth out but does not. The car definitely runs better, sounds better and pulls harder then with the 750. Also spark plugs look good and are not real dark. Do you think a bigger carb might be needed? I also have experimented with the timing and currently have the 25 degree mechanical secondary in with about 14 degrees initial using vacuum advance, also used 16 degrees initial with 28 degree mechanical bushing. Timing changes has not affected the high rpm problem. I have also gone back through and re-adjusted the valves. The car will rev (no load in park) using primary and secondaries with no hesitation, bog or stammer.