I am looking to replace my 600 vac sec with a DP. It is a 305 TPI longblock, LT1 cam (203/208 450/460"), performer intake, L69 manifolds/y pipe/cat, dynomax cat back, T5 and 3.23 rear. It is my everyday car which I drive about 20K a year so gas milage is a consideration. Should i get a 600 or 650 DP. Id like a squarebore since i may upgrade to a performer RPM one of these days. I also want the center pivot floats, i am not happy with the side pivots. What are the list #'s that i should be looking for? Thanks
Sean

 

i'd take a good look at a 600 cfm carb if it were mine.

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-=ICON MOTORSPORTS=-
1st & 3rd

 

the 600cfm w/ vac seconds will be better on gas mileage.

 

You're fighting against yourself here. For mileage, the king of carbs is the q-jet. If you are really concerned about mileage, you won't get an RPM manifold.

Can't have your pumpkin pie and eat it, too.

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82 Berlinetta, orig V-6 car, now w/86 LG4/TH700R. 2.73 unlimited slip. Cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, TBD heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. 0.030 over 396, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

I am not happy with the vac sec holley, it performs inconsistantly with regards to temperature and load on the engine. I am only getting about 17mpg. I think with the DP, the car would perform more consistantly and that i would be able to get better milage, at least when i drive it easy.
Are the holley spreadbores similar to the Qjets (rods/hangers etc), or are they like a squarebore (jets, PVs, etc). I am more experienced tuning holleys and i have all the parts to do so (jets, PV's, accel pumps et al) so i would prefer to go this route if possible.

 

The Holley spreadbores are otherwise built like a typical Holley like what you're used to.

 

If you are looking for performance and reliability... look at the Road Demon 625 for the 305. A q-jet will get you very good milage though. Even on my 350 I was getting 20+ mpg. And that was with CK rods.

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1984 z28 w/ a 357 cu in. monster engine which is looking like the posterchild for Edelbrock... all the suspension stuff... 9-bolt posi disk is in... K&N filter... 93 octane...

-=ICON Motorsports=-

 

My 6210-3 holley spreadbore was getting about 12mpg w th350 and 3.08 gears. Now that I have gone to 4.11 I am getting 8mpg. I would suggest using a q-jet.
Later
John

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82 Firebird,355,Cam 224/234, .466/.488,TH350 Tranny,650 HolleyDP,Hooker Headers(I.E. POS) Manual steering
Best 8th et 8.62@80mph.

 

What kinda mileage can you get with a Road Demon? What is a Double Pumper? It has more pump shot or something? Is a Road Demon a DP?