850 cfm carb recommendation?

[BobB66SS]

Have an Edelbrock 750 cfm single feed 4 bbl w/ vacuum secondaries and elec. choke on my 454 (+.030) BBC. Desktop Dyno simulation on the motor says the 750 is too small, and the numbers jump noticeably (to 550 HP / 590f t-lbs) if I go to an 850.

Have Edelbrock Performer RPM dual plan intake and can't reduce the minimal hood clearance I already have.

Any favorites / recommendations? Anything somebody loved right out of the box?

Thanks.

[rocketman]

Holley 850 dp

[Skip Fix]

If you compare "regular" DP Holleys and their HP line the HPs use a different test pressure, and 850 DP 4781=1000HP.

My current 525 HP 455 Pontiac has a 850 DP that seems well suited for the car.

[Skip Fix]

It just pushed the car to 10.99 @ 124.5 this weekend through mufflers!

[chicane67]

Holley HP 830.... it has a flow rate that will mark your 850 needs and it has the adjustments built into it that the typical 850's lack....

http://www.holley.com/types/4150_HP_Series.asp

I used an HP 950 on a 502 with roughly the same hp/tq numbers you posted and it was perfect.... after we got the emulsion metering and high speed air bleeds tuned. This only took a set of pin vice drills and about two hours to dial it in. The new Ultra HP has interchangeable emulsion jets.... so there is no more need for pin drills anymore.

http://www.holley.com/types/4150_Ultra_HP_Series.asp

[Skip Fix]

As I said the HP series is tested at a different test pressure, kind of like comparing head flow numbers done at 25" and 28". You have to look at venturi and throttle blade sizes to compare them all Holleys vs HPs, Speed Demons vs Mighty/Race Demons.

The 950 HP is actually a 750 sized venturi/body using a 850 sized baseplate. So there is no way it can flow more than an 850 DP. That's why it takes a 1000HP to have the same sizes as the 850. The only Demon that has bigger dimensiions in a 4150 style is the removable sleeve Race Demon with the "silver" sleeves. It has the biggest venturi size of any 4150 style carb.

That's not saying the 950 HP isn't a good carb for a medium sized motor. My motor was still pulling 1-2" vacuum at the top end so possibly needing a little more carb, but I'm not going to a Dominator.

[chicane67]

Hence..... the reason I used an HP 950 for a similar build/requirement.

The reason it may seem that it is a "different test pressure" is because Holly actually "wet flows" the HP vice the standard dry test of the typical carburetors. It kinda throws the 'inHg' measurement out the window in the calculation for gross flow numbers.

[Skip Fix]

The 950 is a nice setup. Some of my carb expert buddies have had problems with the HP metering blocks on some carbs where the IFR is in a spot at the top of the well. My ex Holley engineer buddy said Holley switched test pressures to compete with the cfm claims of the Demon race carbs.

Just check venturi/throttle dimensions to realy compare different series carbs.

Although I do think the Proform 950 body/carb has a bigger than 750 venturi.

[MonzaRacer]

Does the car run good and pull hard? Does it run rich, blow smoke or do any "wrong thing" when you use the engine?
OR are you trying to race a computer program. one if your carb is slightly under square (ie almost big enough)
First of all are you dragracing it or do you drive it on the street? If you drive it on the street the Edelbrock would be better in the long run but if you feel the engine needs more flow they now make the Edelbrocks in AVS style with a simply adjustable air valve over the secondaries.
Most people will jump on the band wagon for Holleys but I really like the Edelbrock/Carter carbs as they are almost completely adjustable from out side the carb. Holleys need a firm understanding of tuning principle of them.
If your just racing the computer , read the plugs, ask friends if they have the size you "think" you need and ask if they might let you try it.
I love how people "think" they need a bigger carb but havent actually tuned what they have to the fullest extent they can.
good luck and if you want to sell the Edelbrock let me know,, I love'em.
Lee Abel

[Shaker455]

Bob,
Stay away from the Holley HP series carbs as there really intended for circle track use.

Better off building them from scratch as I did for people like Skip with all your requirements in mind and it cheaper in the long run.

How about posting some specs of your combo?
Jeff

[Tech @ BG]

Bob,

Your best option is to install a Vacuum gauge in your car, and see how much vacuum you're pulling at WOT. From there an accurate determination can be made on where to go with your carburetor. Usually a larger carburetor will show better numbers on a dynamometer, and simulation but won't always be the best for the real world. If you can give us a list of all your engine and driveline specifications we may be able to point you in the right direction.

Technical Support,

Barry Grant, Inc.

[xx_ED_xx]

I emailed BG and never got a reply and i THINK i was fairly thorough in the details etc. Is there an addy i can try again to?

[Tech @ BG]

I emailed BG and never got a reply and i THINK i was fairly thorough in the details etc. Is there an addy i can try again to?

Sorry about that. If you'll just drop us a PM here we'll be happy to help you. Some computers SPAM blockers will reject our email replies to customers since it's coming from a corporate account.

Thanks,

Technical Support,

Barry Grant, Inc.

www.barrygrant.com

[73ta]

Have Cliff @ Cliff's Quadrajets, build you a Quadrajet. I've seen back to back dyno pulls against tricked out holleys with his carbs putting down more power and better mileage / street manners too.

[speedracer8282]

Cliff is good but expect a year turn aruoud.

[73ta]

Sent my order in in Sept 06, recieved carb Feb 07. He had about a month of delays because of freezing temps back east not allowing wet testing on his test engine.