750 holley vac secondary adjustments from 318 to 390 stroker

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cawcislo

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Setup was 318 engine, ported 360 iron heads, points ignition, weiand action plus dial plane intake, dougs headers, Cam is 224/224 250 465 lift 110 LSA And Holley 750 vacuum secondary. Engine had 7.8:1 compression will be 9.4:1 with the stroker. It is a manual trans, and at aproX 750 rpm idle it had vacuum reading of 14. I believe The jets in it are 68s, and 6.5 power valve. Building the 390 stroker short block, everything else will remain the same for now. How big should I go with the jets and power valve as a starting point?
 
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only your engine can answer that. Personally, I would run a 750 double pumper, especially with the manual transmission
 
Are you recommending the double pumper because it’s easier to tune the secondaries which is needed in a stick car? Should I go 850 double pumper or stay with a 750?
 
Are you recommending the double pumper because it’s easier to tune the secondaries which is needed in a stick car? Should I go 850 double pumper or stay with a 750?
VS will not fly open instantly. They don't have a secondary accelerator pump to support that. On a 4 speed car, 1st and 2nd gear pass by pretty quickly, especially if you have decent gears in the rear end. Do you think the secondary vacuum is opening quick enough to have a "4 bbl" before you bang the next gear? I like the 750 DP in your situation.
 
I like the 750 DP in your situation.
Me too. When I mash the throttle, chit happens instantly, lol.
But another thing I experienced;
There have been situations where I just needed a lil more power, and the VS carb is not good at a lil more. It's great at WOT, but not so much at partially open. There were times it would act like an on/off switch.
The DP is not like that. If you go into a corner a lil hot, you can just dial the power down a lil and then put it right back in, with no shenanigans. And if in mid-turn you want the rear to step out, no problem just feather the power in, whatever you need. In this situation, it sortoff acts like a big one-barrel with very nice progressive power delivery. With a stroker you will grow to really like this. But, in all honesty, not everybody drives like I do, so since you already have the VS, you might as well try it.
Besides, if you have skinny street tires you will never get into those kinds of situations, cuz yur stroker will be a point and shoot kindof car.

As to the actual question; what jets to start; I'll guess 70/78 with a 10.5PV or higher.

Yur gonna love that cam. Don't be afraid to put a free-flowing dual exhaust on her.
I'd run it no more than 2*advanced. With a single-pattern cam, she will lose 2* of effective overlap for each degree of advance. So in at 108*(2* advanced) the Effective overlap falls 4*, from something like 50 to 46. That sucks a bit. But the pressure goes up a bit maybe 3 psi; so that's nice,lol.
 
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