331 Carb choice, the Carb guyz say 750.???

[06cobra]

I spoke with a couple of carb builders and for my setup the flowing recommended
(all are double pumpers)
1.) Proform says 750
2.) Barry Grant says 650
3.) Holley says 650
4.) Jet says 750

Well I'm lost............any ideas.

aluminum headed 331 with roller cam! 5 sp , 98% street driven

 

[65ShelbyClone]

98% street driven

Thats the key right there. A 650 will have slightly better bottom-end response than a 750, and is closer to the "ideal"(on paper) size if you rev to 6500, but a 750 will have a little head space for growth. If you keep it under 6500, a 650 will be better.

 

[iskwezm]

i have a Holley 750 HP on my 349,but its flowed to a 830 CFM and flows more with the blower

 

[Edbert]

I'd use the 650, seriously considered using a 650 on my 357W but was talked into the 750.

 

[06cobra]

The car is rev limited to 6100

 

[ForceFed70]

I'd split the difference and go with a 700cfm model.

 

[06cobra]

das some good thinking.......

 

[jerry S]

I'd split the difference and go with a 700cfm model.

is there such a thing?

 

[Edbert]

I'm not aware of a 700 but you can buy a 725 with center-pivot floats.

Of course you can have a carb reworked to flow just about whatever cfm you want, but I'd let a pro do that kind of thing.

 

[10secgoal]

I'd go with the 750 proform if you already have a Holley. I tried the 650 afterwards, and lost MPH and ET. Slapped on the bigger one, and had it all back. I only have a 302.

 

[06cobra]

Currently I'm running a Road Demon 625 Vac secondary

thanks for all the replies

 

[12sec67]

what heads do you have?

 

[06cobra]

Edelbrock RPM 1.9/1.6 valved

 

[Jimmys66]

I've read 2 mag. articles (take that for what it's worth ) testing 347's with a 650 and a 750 holley. Both tests had peak hp within 1 hp, but the 650 did much better in the low end and had a slight advantage in the midrange.

Both of these motors were done by 6300 rpms (street motors). My take, 650 for a street motor and 750 for an all out race motor with no need for part throttle.

I actually cheated and had a stage 3 650 Biggs holley built that flows 710cfm. It's the best carb I've ever owned. And it looks really nice.

 

[Dark Knight]

Try talking to
http://www.quickfueltechnology.com/

or
http://www.tpcracing.com/tpc_carburetor.html

and see what they say

 

[10secgoal]

I wouldn't touch TPC with a ten foot pole. Have scewed so many people, it's surprising they are still get work.

What are you guys meaning when you say it flows 710 and 830 ?
If a carb is tested a 3in of vacuum, and it flows 710, then it's a 710, not a 650.
When you buy a 650 in a box, that's just a guideline for what you are buying. That does not mean it will flow 650 cfm on your motor.

 

[Jimmys66]

I wouldn't touch TPC with a ten foot pole. Have scewed so many people, it's surprising they are still get work.

What are you guys meaning when you say it flows 710 and 830 ?
If a carb is tested a 3in of vacuum, and it flows 710, then it's a 710, not a 650.
When you buy a 650 in a box, that's just a guideline for what you are buying. That does not mean it will flow 650 cfm on your motor.

Were speaking the same language just using different words.

My carb was a 650 holley dp when it started life and it had some magic worked on it and yes, it is now a 710.

 

[2bav8]

Holley does sell a 700 CFM DP.
I even have a 700 center section laying around.

I use a 650 AND 750 Holley for my 347.
The 650 is tuned pretty conservative for fuel milage and the 750 is optimized for maximum power.

 

[06cobra]

Try talking to
http://www.quickfueltechnology.com/
and see what they say

they also recommended a 750.......... amnit: with annular booster, but on their web page is $515 and he quoted me $610 and won't honor his webpage pricing.... BS. I was calling to order one, but don't think I will now.
I don't tolerate that kind of misinformation to well, if you can't have correct information on your web page then don't run one! http://www.quickfueltechnology.com/cgi-bin/printrecord.cgi?p=95-8156A

 

[06cobra]

I'm thinking of running the giggle gas for a while, then in the future booooost! and it seems they like mech secondarys' (I have vacuum now, it's ok, but wanted MORE )