Carb Question/turbo

[Dentz]

I just picked up a brand new/old version (1992BGrant still in box) carb that
was flowed from the carb shop!It is a 750 and the guy that I bought it from said it flows 922...is this possible...??It still has the 172 butterflies!!I am putting it on a 462 with an old banks single carb twin turbo set up with
a 614int-605exh 114center cam and merlin cast iron heads....Will this be sufficient or will i need an 850!!

[Hotcrusader76]

Congrats on getting that BG carb. The carb shop builds great carburetors. With regards to the claim of 922cfm on a 750cfm rated carburetor. Yes it's possible. It's also possible it can flow well into the 1500s, but that depends on what pressure drop it was tested at.
Something that everyone needs to ask the salesman when you get claims of X amount of cfm on a 650 or even 750 carburetor is what were the parameters of the test. Otherwise you need to assume it was @standard pressure and temp.
Either way you have yourself a nice carburetor. Is this the right carburetor for your application? Well I suppose the question is what application was this 750 intended for? Most of the carb builders these days build them for a particular motor and application. Granted there is some universality in there functioning on most engines but with forced induction set-ups there isn't any room for gambling.
Try to find out more about that carburetor. Ask if there was a blueprint or calibration document that accompanied that carburetor since that's the standard these days on custom carbs.
Good luck on your turbo project.
~Ty
[ April 04, 2003, 04:37 AM: Message edited by: Hotcrusader76 ]

[schiada96]

Ty I have a question. I have a 9377 hp dominator on a twin turbo draw thru 510 chevy. I makes 17 lbs of boost and I guess 900hp. What can I do to help on the top end I seems a little lean and I have reamed the jets to .1450 can I close the high speed air blead to help?

[Hotcrusader76]

At the novice level of modifications, the high speed air-bleeds can be decreased to about 0.024" in order to increase the fuel response on the top-end.
But since you have a 3-circuit carburetor the intermediate circuit can also be lessened to about 0.032" in order to waken up the top-end (high speed bleed).
Also note that the outside bleeds are the intermediates, not the middle ones as many people assume.
Some extensive mods can be peformed to the boosters as well to increase your CFM level and push your signal further to the later part of the RPM. Other than that the HP1150 is an awesome carburetor!
Note- some basic visual inspections should be done as well. Make sure the little intermediate beveled tubes installed inside each throttle bore are directly -up-down-level, meaning the bevel faces evenly down. By turning it around left or right will lean or richen a particular side of the motor. (*lil tuning secret)
Otherwise just make sure they're all even. Sometimes they move around from improper installation (mass produced carburetors)
Good luck.
~Ty

[schiada96]

Thanks for the info. I have notice that all the little beveled tubes are not even. I'll clean them up and make them all the same.
Thanks
Jeff

[Infomaniac]

It has been my experience that when jetting up does not cure the lean condition.
The real problem is not getting enough fuel to the carbs. Especially when the carb is given a very good signal.

[schiada96]

Info I thought that too. I have made some extended runs for a few miles at wot and the fuel pressure has not dropped off. I'm running two holley blue pumps and the tanks have a coastguard no no bottom pickup so its easy to feed the motor.

[Hotcrusader76]

My assumption was that after exceeding the 100 Jet size, your motor was telling you it really liked the fuel. Hmmm.
I agree with aka"Info". The pump might not be holding up it's end of the bargain within your fuel system.
How did you adjust the regulator(s) for proper fuel pressure?

[schiada96]

I turned the little screw on the top of the BG two port reg to give me 7lbs of fuel pressure

[Infomaniac]

Try 8.5 or 9. The needle seats should hold 9.