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Racing Fuel Systems • View topic - Carb recommendation
Page 1 of 3

Carb recommendation

PostPosted: Sat Jun 11, 2022 12:47 pm
by Tonys Toy
Looking for a carb recommendation from the carb gurus.
Looking for Holley carb to be used on 396 BBC in a 1969 Chevelle SS. Engine is a Mark Jones unit with all the attention to detail.
Engine info:
396" cleaned up to 412"
Compression - 10.25 - 10.50
Cam - SFT w/264*/264*@.050" & .600" lift I & E on a 108*.
Heads are MJ massaged oval ports.
Intake is stock rectangular dual plane.

Trans is a 5 speed with a 4:11 rear gear.
Thanks.

Re: Carb recommendation

PostPosted: Sun Jun 12, 2022 1:15 am
by Right hand drive
Vehicles intended use?

Re: Carb recommendation

PostPosted: Sun Jun 12, 2022 3:34 am
by Tonys Toy
Forgot about vehicle use. Car will be mostly street driven with maybe a few passes at a test & tune to see how well it really can run.

Re: Carb recommendation

PostPosted: Sun Jun 12, 2022 6:31 am
by GTO Geoff
Edelbrock 800 AVS2 with annular boosters.

Re: Carb recommendation

PostPosted: Sun Jun 12, 2022 12:19 pm
by Tonys Toy
Was thinking a Holley carb, not enough familiarity with the Edelbrock carbs. Also want to keep the look of the L78 with a Holley.
Thanks.

Re: Carb recommendation

PostPosted: Sun Jun 12, 2022 6:38 pm
by rgalajda

Re: Carb recommendation

PostPosted: Sun Jun 12, 2022 8:48 pm
by Tonys Toy
Yes Mark Jones is Vortecpro. He seems to know how to make the rectangular port intake work very well with the oval port heads. I know this for sue because my son has one of his engines with that combo. It really runs strong.
Interesting you should mention the original Holley carb. I have an over the counter replacement (3878261EH) for that carb. It has the 5271 primary metering block and a 4519 secondary block. Came with 8.5" power valves. 70 pmj & 76 smj. Don't recall the bleeds or emulsions. Need to check them.
May be an option to have someone professionally go over it . My only concern it that it may not be enough for this engine.
Thanks for the recommendations.

Re: Carb recommendation

PostPosted: Mon Jun 13, 2022 2:17 am
by Right hand drive
Hard to go past rgalajda’s recommendations for intended purpose. There’s Brawler BR-6257 or Holley 4780 if your preference is mech sec. if you don’t have one get an AFR gauge no matter what carb is selected. There will be some dialing in needed with that cam.

Re: Carb recommendation

PostPosted: Mon Jun 13, 2022 1:21 pm
by rgalajda
So let's address some of Holley's bull**** on there cfm ratings they used for the war they probably encountered with the competition.

First the
4346 OEM 780 Holley 1-3/8 prim venturi, 1-7/16 sec venturi, 1-11/16 throttle bores
3310-1 780 Holley 1-3/8 prim venturi, 1-7/16 sec venturi, 1-11/16 throttle bores

Quick Fuel
BR67258 770 1-3/8 prim venturi, 1-7/16 sec venturi, 1-11/16 throttle bores ( improved contoured venturi )
BR67257 750 1-3/8 prim venturi, 1-3/8 sec venturi, 1-11/16 throttle bores


80531 850 Holley 1-3/8 prim venturi, 1-3/8 sec venturi, 1-11/16 throttle bores ( how can that be/ the same non contoured venturi )
4780 800 Holley 1-3/8 prim venturi, 1-7/16 sec venturi, 1-11/16 throttle bores

Re: Carb recommendation

PostPosted: Mon Jun 13, 2022 1:42 pm
by rgalajda
They didn't want the quick fuel carb look better even though they now own quick fuel.