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Dual Quads

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fasterthanu

Guest
I have a 1976 L-48 Stingray, I just put a nice cam in, 480 lift =) and dual quads on. Doesn't seem to pull as strong as my dad remembers dual quads to pull. Doesn't snap your neck. Both are opening fine..... Thinking of trying quadrajets on them, due to their monster secondaries. Currently have Rochesters on them..

Has anybody run their vettes before, and after installing dual quads? 1/4 times, how much of an improvement.

Post your responses, doesn't have to be a 1976 vette =)
 

Tom Bryant

Well-known member
Administrator
Joined
Nov 9, 2000
Messages
7,203
Location
Edgerton, Ohio, United States
Corvette
1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
2 4's

Of course it all depends on the condition of the engine and state of tune. If you have the single cat exhaust system you may be trying to push 5"s of exhaust down a 2 1/4 " pipe. How is your distributor set up, total timing ect? Are the carbs jetted right? What Rochester carbs are you running? You may be over carbed. At least until you can free up the exhaust. A Q-Jet is over 700cfm by it'self. 2 would be enough for an Allison V12. Check the Toolbox calculators in the Hot Links on the front page for a Carb CFM calculaor to help you get the right carb size for your engine.

I remember in '65 when the Q-Jet came out that Offenhauser had a few odd manifolds for them. One, pictured in Hot Rod, was a dual 4 bbl manifold. I can't remember if it was for a small or big block. 1400-1500cfm somehow seems a little excessive for a mild street engine. I wonder if they ever sold any of these. You would need to hang a bucket on the tail pipe to catch the raw gas that ran out the back.

I did the early Corvette dual quads, cam and head work at the same time on my '59 283. That was in '71 and I took the car apart before I had much time to play with it. It's still apart.

Tom
 
G

garin1

Guest
dual quads

had dual quad edelbrock 1404's on my 68 with a 350cid and edelbrock.it sounded great when the secondaries opened up but it was to much fuel.my last run on the track was 14:45 after coming into forth to slow and i think all the extra fuel helped to bend the motor.
 
F

fasterthanu

Guest
I got lucky. With the cam I put in, 480 lift, can't remember the duration right now, the dual quads really seemed to help. If I run a trip to my dads, 101 miles expressway, with only one 4 barrel connected, it is a progressive linkage, with it set so only operates one carb, I consistantly get 11mpg..... Running off both 4barrels, move throttle, they both move at once, consistantly 15-16mpg... Must be because of the cam....
 

Tom Bryant

Well-known member
Administrator
Joined
Nov 9, 2000
Messages
7,203
Location
Edgerton, Ohio, United States
Corvette
1959 black 270hp (9/2/69) 1981 Beige L81(10/20/80)
lousy fuel distribution

You get lousy fuel distribution running off of the primary side of the rear carb. The front half is starving. Using the primary side of both carbs gives decent distribution and allows much less throttle to go the same speed.

Had a '62 Bel Air bubbletop with an inline 6 that picked up 4 mpg when I went to twin carbs and splits.

Tom
 

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