L-82kid

I have a 350sbc with 144 supercharger at 7psi of boost, 234/244 .522/.544 112/110 blower cam, with a stick and 3.73gears. Car is 3240lbs

I had a 750cfm mighty demon blower carb with annular boosters which i just got rid of due to several quality control issues. After dyno tests and tuning it was determined that the 750cfm was too small for my set up. it required going up 15 jet sizes on primary and 17 jets sizes on secondary and swapping H.S. Air bleeds to get the AFR in correct range for motor! motor was making 460-470 flywheel horsepower 510' lbs.


I was suggested by Holley tech, a motor builder, and the dyno guy to run a 950cfm. I called quick fuel tech and was told to run a 750cfm again! So I contacted a few carburetor builders/parts places I found online and was suggested to run at least an 850cfm if not a 950cfm.


I have a 600 dollar credit at JEGS so I'll going to order a carb for them and have to choose between a quick fuel 850 or 950 blower carb..... or a holley 950hp blower carb.


Any feedback on quality and performance of quick fuels??? the holley 950hp is about $125 more then quick fuel but has a rep. I dont care about the extra money I just want to best carb for application.

Go-Gone

I have a Quick Fuel 750 mechanical secondaries on the 347 stroker in my 66 Mustang Conv. I can say it is probably the best carb I have ever used with absolutly no issues from day one. There is no blower or nitros and engine makes about 425 HP.

73BLWN

If you recall, I have two blown 400ci sbc's one has the B&M 144 blower and one has the 6-71.

I had similiar concerns about carb sizing with my 144 blower motor. I run a Holley 800 double pumper on it , and had to jet the primaries up 10 jet sizes. I don't recall there being anychanges to the secondary jetting.

The big blower was running two slightly modified 600 holley vacuum secondaries that were boost referenced. We measured the air flow of the 600's, and recorded 585cfm at 6500 rpms.

My current engine builder doesn't consider boost referenced carbs necessary, or desirable. He recommended two 950HP's for the big blower motor. This is what I ordered.
2 510-0-82951 CARB 950 CFM D/PUMP POL 546.99 1,093.98

Both motors have been rebuilt over the winter and are going to be dynoed in the up coming month/months. I plan on trying one of the 950HP's on the little blower motor. FYI, the little blower motor will be for sale after it is dyno'd. I expect 500HP+ 550trq+ at the flywheel.

So, although your motor is 350ci, and mine is 400 ci, I would suggest the Holley 950 HP. I have the little blower motor on my runin stand and have swapped all three carbs on to the motor. The 950 throttle response is the best. Unfortunately, I can't speak to what it will do under load, but I believe it will work great.

Good Luck and let us know how it works out for you. I'll do the same.

brando1118

I have a QF750 DP. It is an awesome carb. Believe me; you want the adjustable IFR's and adjustable high/low spped air bleeds. Really nice carb.

ajrothm

Contact this guy..... he'll get you right....

http://www.pro-system.com/

L-82kid

Ive heard of that company, but I returned my demon through jegs and i have to use the return credit toward another carb that they sell.

L-82kid

I found a formula online for determining best CFM for a supercharged motor:


(CID X RPM / 3456) X (boost/14.7 + 1) = CFM



for 350ci @6000rpm peak and 7psi it came out to.. 896.86cfm


I'm confused as to why the quick fuel tech told me not go over 750cfm, even though my last 750cfm was too small.lol

73BLWN

Thanks for sharing the formula. I'm gonna speculate that conceptually it's similiar to the NA carb formula. Each engine can make different HP/TRQ at certain RPM and or Boost verses another engine depending on heads, cams, etc. The formulas are a good reference for carb sizing, but experience will teach us the overall best selection.

The formula does lead me to believe that my little blower motor will like the 950HP over the 800dbl pmpr. The dyno session should be informative.

Look at the throttle bore differences between my old 600cfm vacuum secondary holleys verse my new 950HP. I'm excited to try out the 950. My research indicates the 950's work excellent on motors making as little as 450hp.




Here is my 800 Dbl Pmpr.


It's tough to get everyone to agree on carb sizing. Generally speaking you can't over carb a blown motor, but you surely can under carb one. Interestingly, I was at the Carb Shop in White Bear Lake Mn picking up a few parts and told the owner about my motor, and that I was buying 950's. He thought it was overkill. We both thought 800's would be a perfect choice. He didn't think I'd have problems, but felt I'd reach my goals easily with the 800's.

Sorry, I have no experience with Quick Fuel Carbs.

L-82kid

I was refunded my money in full for my demon so I can get any carburetor. I contacted a few custom builders and I'm pretty sure I'm going to have pro-systems build me a custom 4150 for my combo.

73BLWN

I'm curious, in talking with other custom builders, what advice did they give you in regards to boost referenced or not? As I mentioned the builder I'm working with doesn't feel they are necessary. The previous tuner/dyno operator I worked with felt the same way. I'm not saying they are right, I'm just sharing information I've been told.

I know how to modify Holleys so they are boost referenced. A holley technician sent me a drawing specifying the necessary details so I could modify my 600 vac secondaries. For now, I'll try following the "experts" advice and tune the motor with the non-boost referenced carbs.

Anyone else out there get any specific advice or hear any comments about the value of boost referenced carbs in supercharged applications?

L-82kid

pro system said boost ref carb is not needed on my set up, the custom carb will be tuned to work better without being boost referenced.

auavette

Just ordered 2 carbs build to my engine specs from Pro-System.
My engine is a 496 with 8-71 blower

dochorsepower

When I was running a 144 B&M with a Holley 850 on my 350, I found I had to change the power valves to 4.5 because the blower develops so much more vacuum at the carburetor.

L-82kid

my new custom built pro-system carb should be here next week around tuesday or wednesday. Then my next mod will be swapping to an electric fuel pump and 8an lines.