How do you guys adjust your Double Pumpers? I heard that you have to close the secondaries then adjust the primaries. Do you do this while the car is running or no? What's the base amount of turns do you do for the front and back screws. The exhaust is blowing alot of smoke.

What kind of smoke exactly, blue, white, black? What are you adjusting idle mixture setting, if the motor you have is as bad as the sig shows you might be one of the guys that needs to drill a tiny hole in the primary butterfly to allow more air in than the idle circuit will allow so it won't produce the overly rich condition at idle, like I'm assuming your describing. I know on VS there is a small set screw that you can only access form the underside of the carb when it is off the vehicle to open the butterflies a little more, never paid attention to the DP I have now. As far as setting the mixture screws basics, a good base that holley reccomends is turning the mixture screws all the way in then back them out 1 1/4 turn for a starting point. Yes the car needs to be running when fine tuning the mixture adjustment and don't worry about trying to close the secondaries to adjust the front, I never did. Once you start screwing the screw in or out you'l want to listen to the engine, it'll either start to sound bogged and rough, then your going the wrong way, once the rpms come up and the engine smoothes out that'll be the "sweet spot", go a little more 1 way and the other to make sure. Do this for all four circuits.

I did this earlier today. The primaries are 1 turn out, and I believe the secondaries are the same. I adjusted the pump cams also using the #2 hole on both cams. This helped the hesitation off idle. I backed off the timing and it ran pretty good in the driveway. I am going to try some 110 octane tomorrow, and see if I can get any more out of advancing the timing. I had a real bad gas smell at idle, but that has, for the most part, gone away.

The car dies towards the end of the track. I pretty much eliminated the timing and fuel pressure as a problem. Timing at about 10 degrees initial advance and fuel pressure abou 6.5psi. The guy who built my motor says that the carb has to be jetted up. What screws on the carb need to be adjusted other than the A/F ratio and idle screws. I do not have a vacuum advance. Anyone have any suggestions on jets. What size are the ones in there? I dont want to buy tons of jets if I only have to use a couple. Im new to carbs, excuse the ignorance.

If your new to carbs your gonna have to invest some time and money to get this baby dailed in, reusable nylon bowl gaskets and reusable bowl gaskets. From looking at your motor sig your fuel pressure is not high enough, jump it to 8psi now!, that will help, second your waay under carbed hence the fall of at the big end, I have a 9:3.1 355 and I'm running Holleys race 830 double pumper, picked up .3 just bolting that on, used to have a 750 VS. Holleys are usually sent rich so you'll probably have like 72-74 in front right now and 80-82 in the back. Holley has jets ranging from 59-99, your better off just to buy the $40 kit so you'll alqays have them and until you get your plugs to read right, those trips to the parts store and @ $5 for a pair of jets you'll have $40 spent pretty quickly, that's if the plugs are waay off at this point. If they're way white after you make a hard run go up 4 sizes (70now, jump to a 74) Another thing that people take for granted is their intake, If your running a dual plane I've seen some motors where some of the plugs are black and some of the others are about right. It's because the front is feeding one way and the back are feeding another way in a criss cross pattern. With an open plentum all the fuel is being dumped into a huge pot so to speak and it's being sucked at a similar rate. So you can get away running bigger jets out back cause after they come in the motor can use the extra fuel, cause by then it's usually spinning up. Make sure your power valve/s are right to your motor that'll help also. The only true way to dail it in is by trail and error, you'll get tired of draining gas and removing the bowls, but if you want max performance that's the price you pay, and it's alot easier and cheaper than shucking a motor too. But like I said your pressure needs to come up, Holley's can take 9psi before they push fuel past the needle and seat, so 8 psi is about as close as everybody runs them. Are you running a mechanical or electric fuel pump? I know you just spent some jack on this new carb, but for a hopped up 383 yoou need more, plain and simple. Holley's new 950HP is finding it's way on just about everybody's car at the track cause it's a typical .4 bolt on deal, for the slighty and highly modified motors. Look back at my combo and see for your self, short times dropped .06 1.88 to a 1.82 and I went from consistent 14.0-14.1 to consistent 13.6- 13.70's, and mines a baby compared to yours. Just from a 750cfm to 830 cfm.

The carb is literally a month and a half old. The guy who built my motor suggested it and highly recommended it over a 800 or 850. By jetting it up will it perform close to an 800 or 850? It is a mechanical secondary. Also I am running a single plain intake, the Victor Jr.

What are the power valves to the motor?
what else should I adjust rather than the jets?
Thanks for reply, very helpful, keep it coming!

Thr guy that built your motor is either uninformed or having a brain fart, you have one hellava motor, and motor are a big air pump, the more air you dump in the more fuel you can dump in and the more power you can make, if the motor is set up to efficiently use the increased air/fuel mix and I'd say your is a PERFECT candidate. You can jet up all day long, but the simple fact of the matter is you have a 750cfm carb, so, it will only flow 750cfm of air, and you can only mix soo much fuel with the 750 cfm before you start loading it up. Hence a 830 like mine or a 950 is a bigger "air intake" so by allowing more air into the motor you can add more fuel to the motor and hence more power. They have a fake *** formula for figuring the needed cfm for a motor they take the max rpm, times 3456 or something and divide it by how efficient the motor is, Can't remember the exact formula, but I remember when I first saw it, the math said mine need a 500 cfm carb. I had a 600 and was running mid 14's. So in my eyes that formula is bunk. As far as choosing the right power valve, they say to run the car down the road at about 45mph and check the vaccum, then you get a power valve about 2" below the lowest reading.
Try this web site and see what you think it should be just the ticket for your problems and questions
www.bob2000.com/carb.htm
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