i need help, how to set a dual quad with 2 holleys double pump, in my small block chevy 350, when you run the car there's a bad acceleration with rough idle, i don't know about the float, jets, everything, i checked the spark plug and seems to be good, maybe little poor, a spark plug was wet .............! please let me know
What size are the carbs? They should have a LIST number on them near the top. You can look that up to see what the CFM rating, is, and what size jets they came with originally. You set the float levels using the screw and nut on the top. The screw locks it in place, the nut screws the float valve up or down. Remove the plug on the side of the bowl, run the engine, it should have the fuel just slightly runnig out the hole. If it's too high, screw the float valve down. If it's too low make it go up. It takes a little while to see the effect of lowering it. Be careful! don't start a fire with the fuel on the engine. Take the carbs apart to see what the jets are, you probably want to start with the original jet size. If the transmission and rear gears are not set up for drag racing, then you might have trouble getting it to accelerate well at low RPM. There will be too much airflow thru the carbs, not enough air velocity to "pull" the fuel thru the jets. Smaller carbs, or steeper gears, or more stall speed in the transmission torque converter will help.
A lot of particulars, left for us to guess on. What engine? (I can see it is a small block Chev), but what c.i., bore, cam, gearing, etc?. What size Holleys are they?
i bought the manifold unit with the carbs at carlisle 2 years ago, the guy tells me it was a dual 600cfm ,i never checked if it's true or not. the camshaft is a mid cam 244 duration, the bore is stock, the renforced springs are from isky, the puch rods, stainless steel rollers are new, and the valves too. the car run a T10 manual 4 speed trans and a stock 12 bolts positraction rear from a 1969 chevy...
How many cubic inches, is it a 350 engine? The rearend could have gears from 2.56 to 4.11, maybe you could see what the ratio is. Jack up the rear of the car, put it on stands. Turn the wheels so both wheels turn exactly one revolution, count how many times the driveshaft turns. That is the gear ratio.
What are the List-# on the carbs choke horn??? Those look like List-1850 which are 600 cfm carbs with vacuum secondaries... I could be wrong...
First off, cross ram isnt the best for getting a smooth idle, long runners mean it takes a long time for the gas to get from the carb to the cylinder at low rpms there is lots of tuning needed to make stuff run right, unlike tunnel ram both sides of the motor are seperate intake systems, so both carbs need to be 100% identically tuned Good luck though, it is really a mean looking setup!!!
I can almost guarantee you that it is the power valves. Jet size gets blamed nearly every time that a blown or wrong size power valve is the real problem. Here is a link to instructions on picking the correct valves and adding protection for the valves if your carbs do not have it. http://fasthotrods.com/index.php/technical-information/doc_download/38-powervalves
I'd start by ensuring the carbs are in great shape, so I'd rebuild both. Then check the accelerator pump cams to see what cam is in place now. You'll want to go with a cam on the Holley carb that gives you a big shot of accelerator pump off idle to overcome the air volume you're putting to the engine. I'd also suggest you change to 50cc accelerator pumps when you kit the carbs. I'd also start with stock jet, so see what carbs they are and check the jets while you have them apart to ensure they are what came with it, and not oversized. I would go larger on nozzles, to help the larger squirt get to the engine better, but size will have to be adjusted after all the other changes. Nozzles are so easy to change on the car that I always do them last, once the carbs are set up.
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