Ok i have been reading in popular hotrod that dual plane intakes like bigger carbs. If this is true what do you think about this. this is a 464 -1975 block and Stage 1 heads no port work on heads -JE Pistons for about 9.5:1 comperession -Eldelbrock Dual Plane intake with 1" spacer -Holley 750 Vacuum Secandary -headers -6al box -msd distributor and coil -electric fuel pump -2500 Coan Converter in a TH350 Would i be better off with an 850 Double Pumper or would that be hurting me? I haven't run it in the 1/4 but pretty confident 13's out of it. Runs really strong. How do I know if a bigger Carb will help it. By the way I really don't want to mess with a Quadra-Junk. I never did like them on any of the chevy stuff. thanks bryan
carb Hey bryan,Trust me , Go with the 850 db Youll be fine .. :TU: Stay away from the vacuum sec carbs...
Well I always heard that the vacuum secondary carb were good for street application. Is this true or not? this is mostly a street car and might see the track 2 or 3 times a year.
I thought I should be in the 13's myself. Short of the Stage 1 heads we are set up similarly. My best run last night was a 14.58 @ 95.5mph . I thought my car felt strong too. I am going to try an 870 Holley vac sec. carb early next week. Before you jump, let me see what the increase in cfm does for mine. Unless of course, you just can't wait :grin: Then we could compare results.
Is it true that you can determine if your engine can utilize a bigger carb by running a vacuum gauge off the intake (or carb port?) and reading it at WOT? If there's vacuum still showing on the gauge at WOT then a bigger carb will improve performance? I'm about to do this test with the engine in the car and a vacuum hose/gauge extending into the car. Where's the best place to take the vacuum reading from? Idealy, there should be ZERO vacuum at WOT, correct? Thanks.
bryan, there are 9 sec. big block chevy superstockers who have to run the 750 quadra-junk stock carb according to the rules, so don't discount that carb alltogether. you might be better off having your carb professionally done rather than buying a bigger off the shelf carb. the really good carb guys can give you fuel curves that almost equal fuel injection. as for the intake, if the stock stage 1 head flows 230cfm you can bet that dual plane intake is killing at least 20% of that airflow. air (like water) does not like to go around corners, and the faster that air flows around a corner the more turbulant it gets, further reducing the flow. just look down the carb hole of a dual plane intake and imagine the air trying to go around all those corners at 5000rpm. matching carb, intake, cam, exhaust to your engine is an art. the new car mfg.'s are finding this out and getting fantastic power gains and gas mileage too. good luck
Hey bryan, did you try to check the jet sizes in the primarys and front squirters?? the car may be running lean... the primarys jets should have at least 78 to 82. The front squirters should be at least 35 ...it should be stamped on the front of the squirter what it is ...good luck :TU:
Well squirter is only a 28 front jets are 75 and rear are 78. It prob. need bigger jetting size. Also, I have always heard that if you can get a 750 to flow like an 850 you are 10times better off because of less volume and more velocity. I am pretty sure taht is true. I know a local guy pretty good. His name ios Jim Evans and he does race carbs. Last time i visited him he was pulling a 397 ford that make 799.7 hp. thats awsome ! he knows his carbs so maybe i will have him do some work to it. thanks
MY OPION IS THE RACE CARBS LOOK NICE , BUT A WELL SET UP QJET, WILL RUN JUST AS GOOD, BUT FOR A LOT LONGER, I HAVE HAD ONES THAT HAVE RUN FOR OVER 100,000 MILES AND NOT ADJUSTED. AFTER I GET MY GS IN THE 11'S WITH MY QJET, I PLAN ON TRYING A DIFFERENT CARB JUST TO SEE FOR MYSELF, I HAVE READ ALOT OF TEST, AND DYNOS, AND UNLESS YOUR RUNNING WELL OVER 500 H.P. THERES NOT MUCH DIFF.
I've not even touch my Q-jet since I re-jetted it 8 years ago for headers. Seventy five percent of the tuning can be accomplished externally. I get great gas mileage when I want to :TU: and terrible gas mileage, when I want to :Brow: OK - so much for the Q-jet plug. A decision to run a double pumper Holley should be based in large part on your tranny choice. Manual - double pumper; Auto - vacuum.
Yes, that is correct. At WOT Also from my experience, dual-plane intakes do not like carb spacers. They really mess with fuel distribution and vacuum signal to carb. Save spacers for single planes, IMO, which is what I would use. Double-pumper Holleys don't like tall-freeway gears and stock converters, something to think about.o No:
