Cliff's Quadrajet Parts and Rebuild Kits

General Category => Quadrajet Carb Talk and Tips => Topic started by: 70GS455 on November 22, 2020, 08:28:41 PM

Title: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: 70GS455 on November 22, 2020, 08:28:41 PM

Wrapped up a few days of testing a 482 BBB with a 7043240 recipe 2 plus 1.240" air door and AX rods. Ended up at 586 hp and 603 ft lb. Best we could get with a 950 Ultra HP was 595 hp and 621 ft lb so only  9 hp and 18 ft lb better than QJ. Had 2" vac with the  Qjet at 6000 rpm

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: Cliff Ruggles on November 23, 2020, 01:25:23 AM

Nice.  I've build a few "max effort" 455 Buick Q-jets with the outer booster rings removed and they support big HP and run well at the track.  I save those builds mostly for FAST Class set-ups but have a few in full race applications well into the 9's in the 1/4 mile.

With only one N/S assembly fuel delivery MUST be adequate for the power level but otherwise the carbs do a fine job of keeping up.........Cliff

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: 77cruiser on November 23, 2020, 05:00:12 AM

Nice.

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: lightning boy on November 24, 2020, 05:04:30 AM

Is a 7043240 a 750CFM casting?

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: 70GS455 on November 24, 2020, 07:16:19 AM

Quote from: lightning boy on November 24, 2020, 05:04:30 AM

Is a 7043240 a 750CFM casting?

No, 800 CFM

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: Cliff Ruggles on November 25, 2020, 04:00:42 AM

The larger castings actually flow "850" cfm, not "800".  With the booster rings removed they are 897cfm with the rear air flaps set to 1.240-1.250"........

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: 70GS455 on November 30, 2020, 12:53:33 PM

Quote from: Cliff Ruggles on November 25, 2020, 04:00:42 AM

The larger castings actually flow "850" cfm, not "800".  With the booster rings removed they are 897cfm with the rear air flaps set to 1.240-1.250"........

How much would removing the outer booster affect drivability ? How much would setting change?

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: lightning boy on November 30, 2020, 01:49:45 PM

Just curious, was this with a dual plane intake or single?

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: 70GS455 on November 30, 2020, 06:22:24 PM

Quote from: lightning boy on November 30, 2020, 01:49:45 PM

Just curious, was this with a dual plane intake or single?

Dual plane, Edelbrock B4B (similar to Performer) port matched

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: Cliff Ruggles on December 01, 2020, 03:42:12 AM

You will loose some efficiency removing the outer booster rings as it effects sensitively to the jets and atomization of fuel.

Even so when calibrated correctly single booster models work fine for street use and excellent drivability, just expect a little more throttle angle to be required and a little more fuel consumption for "normal" driving.......Cliff

Title: Re: Dyno'd a 7043240, 586 hp and 603 ft lb
Post by: lightning boy on December 01, 2020, 09:21:17 AM

Do you guys feel like this is about the upper limit for a Qjet on a dual plane manifold? 586HP?

I know some racers around here say a dual plane takes a larger carb than a single. because the engine only sees half the carb ant any one time.

Thoughts.

I have hopes in the future to build a 427 sbc and make 600HP, but I've never seen that out of Qjet with a dual plane and I don't have the hood clearance for a Dart, Victor, etc. single plane.

Good work guys. I love dyno and track numbers with Qjets!