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Old 12-25-2011, 07:25 PM
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Carb Size And Type For Sbc?

I Am Finishing Up A New 383 Sbc Engine And Need To Purchase The Carb And Intake.

The Combo Is As Follows:

10.5-1 Comp

.480 Lift/230 Dur.@.05 On A 108 Lsa.

I Am Leaning Towards An Edelbrock Rpm Air-gap Or A Professional Products Crosswind And 650 Holley Double Pumper.

Does That Sound Ok Or Should I Be Looking Into A Open Plenum Type Intake Manifold With A Bigger Carb.

The Car Is 2500 Lbs., Auto Trans/3000 Stall, 4.56 Gears.

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Old 12-25-2011, 07:54 PM
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How will you use it?

I know this is about Hot Rods and Street Rods but a reality check seems needed here. A few questions.
What will this vehicle be doing 90% of the time?
Based on compression and cam it sounds like a hot daily driver. If so I'd go with an Idle to 5500 manifold and a 625 cfm Carter AFB.

If you want to play light to light or run flat out often, I'd go 1500- 7000 manifold and a 670 Holley street avenger or if you can afford to waste gas and change plugs often a Holley 750 double pumper.

I didn't know Holley made a 650 double pumper. I know they made, perhaps still do make, a 650 vac secondary Q-Jet replacement but it's hardly a performance carb.

What you don't want is an engine that leans out on the top end because it's not getting enough fuel, or one that bogs down off the line because it's getting too much.

Just my 2 cents. Get more opinions. Haapy
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Old 12-26-2011, 05:33 AM
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Quote:
Originally Posted by SPEED MASTERS CC
I Am Finishing Up A New 383 Sbc Engine And Need To Purchase The Carb And Intake.

The Combo Is As Follows:

10.5-1 Comp

.480 Lift/230 Dur.@.05 On A 108 Lsa.

I Am Leaning Towards An Edelbrock Rpm Air-gap Or A Professional Products Crosswind And 650 Holley Double Pumper.

Does That Sound Ok Or Should I Be Looking Into A Open Plenum Type Intake Manifold With A Bigger Carb.

The Car Is 2500 Lbs., Auto Trans/3000 Stall, 4.56 Gears.
With it being so light weight, this gives you a lot of latitude when it comes to intake selection.

The best all 'round intake in my estimation is the RPM or clone, but not the air gap. I think the air gap offers very little additional performance once the engine is up to full operating temp- but therein lies the rub. The AG takes longer to reach a stable temp than the non AG intake, so until it's warmed up fully the performance isn't going to be what it should be.

But a dual plane is optional in your case, given your engine/vehicle combo. The rule of thumb is usually a dual plane for engines like yours, providing its installed in a vehicle weighing something like 3500 lbs., which would need more bottom end to get the vehicle moving. But w/the weight and gear ratio you have, this is not an issue. In fact, trading some bottom end for midrange/top end might even make for a quicker 1/4 mile- again, in this case. Traction will be hard enough to find, so trading some bottom away could help the 60'.

I'm a fan of the Holley 4777 650 DP. I have used that carb successfully on engines as disparate as a 327 SBC to a Pontiac 455. It will work in your case, especially if you were to use a single plane (generally a slightly smaller carb can be used w/an open plenum). But a Holley 750 vacuum secondary like the 3310 could be a good choice as well. It would work well on either type intake. Had a friend who insisted I install a 4778 (700 DP) on his Pontiac 400 (I wanted bigger) and it ran very good w/it.

I can't really comment on the newer Holleys like the Avengers. I haven't owned one and have only tuned/rebuilt a couple and all I can say is I'm not particularly impressed. Edelbrock carbs are a Carter clone, if I were going to use one it would be the Thunder series w/adjustable secondaries, not the plain vanilla Performer.

BTW, using one of the common CFM calculators (CARB CFM = Cubic Inches x Max RPM / 3456 x VE%), a 650 is as small as you would want to go, practically speaking. And I'd say a 750 would be the upper limit.

That cam will want a fairly good amount of initial timing. Total timing will depend on what heads you have, fuel and so on. But keep a close look-out for any signs of detonation. I suspect you're up there as far as dynamic compression ratio goes.

Last edited by cobalt327; 12-26-2011 at 05:39 AM.
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Old 12-26-2011, 11:50 AM
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The best street carb ever built is the Quadrajet. You can get one for your app at several vendors and they will outrun, out mileage and outlast any Holley or Eddy.
If you insist on a Holley, you need a vacuum secondary and an electric choke like the 0-8077 or similar.
I like the AG intakes in a warm climate but they can have drivability problems in the cold.
I have seen the proffessional products intakes with the runners so far off you can't fix them. Professional they are NOT.
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Old 12-26-2011, 03:16 PM
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I have to agree with Robert. The quadrajet is the best street carb out there! There is a Book called Cliff's Quadrajet's get the carb and the book you won't be sorry!
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Old 12-26-2011, 07:24 PM
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