Opinion Please

[TERMN8OR]

I am currently running a Holley 4150 HP, 950 cfm, Square Bore carb.
I have a 502 w/ stock intake and full roller cam.
Do you think this is too much carb for this motor ?

[ProdigyCustoms]

Yes, I would run a 750 on that motor.

I would run a Holley 750 Ultra Avenger on it. I have sold and run these on 500HP to 600HP motors with great power and street manners.

They run $500

[TERMN8OR]

Frank,
would you be able to put something together for me ? Correct jetting and sorts ?

It seems that me current holley has quit on me. My car current won't start unless I floor it. Once it's starts, it will only run at around 1800 RPMs, and runs very rough. It will not idle at all. Just started doing this last night, so I'm not sure what happened.
Any suggestions on what to check ? I tried tapping the carb a few times in case the float was stuck, but no luck.

[TERMN8OR]

I also pulled all the plugs out, and they don't look too good.

[ProdigyCustoms]

Probably is a stuck float. You can pull the site screws out of the side of the bowls and see if fuel runs out.

[tonykim]

I've had pretty luck with Edelbrock carbs as well. 750 cfm and also the spring and metering valve kit to dial it in.

[TERMN8OR]

Frank, Are you around tomorrow ? Can I call you to discuss a new carb ? I'd like to get something from you ?

[NASH JUDGE]

that carb should be fine if not great w/ that 502.
pull the bowls and metering blocks off & spray em out w/ carb cleaner. blast the needle and seats. put in a 5.5 powervalve & drop 1 jet size in the primary.
same w/ the back but leave the jets alone. 6 to 6.5 fuel psi . set the floats properly. make sure there is no slop in the squirter diaphram linkage.
b bump up the timing a hair in that 502. set the idle with your idle mixture screws and the primary idle screw.
you should be rockin.
idle at 850 - 950

[NOPANTS-68]

IMO- it really depends on how hard you intend on winging this thing. CFM demand is usually based on c.i.d. versus RPM. Having said that, I really struggled with my HP950 on my 468. After speaking with some carb pros they explained to me that the 950 does have some issues with regards to carb signal and idle circuts. I ended up swapping to an HP850, 6.5 PV, 76/80s and a 37 front shooter. The car felt like a AA Fueler after the swap, but was far more crisp, and didn't feel so fat. Your engine may ask for slightly different settings, but that's what worked for me. If you get stuck, call Bob at Comp. Carb.

http://competitioncarburetion.com/

[ProdigyCustoms]

I have a lot of experiance with 950 HPs. Been running them on a couple street drag cars since the mid 90s. My street racer needs 950CFM on the big end. Problem I have always found has to do with signal. Long story short, I can get it to idle great, cold start no problem, perfect A/F on motor or notrous on a run. but in the middle cruising, it is one cranky bitch! Always fat, can;t tune it out. Not with air bleeds, power valves. it runs fine just KILLS fuel!

I doubt he is making more then 550HP, the 750 will drive sweet and will be plenty for occasional hell raising.

[TERMN8OR]

Frank, Sorry I didn't get back to you yet. Got wraped up at work. I'll get with you by weeks end.
Quick question about the new carb... Are you recommending Vac Secondary's, or the Double Pumper ?

[Shaker455]

I am currently running a Holley 4150 HP, 950 cfm, Square Bore carb.
I have a 502 w/ stock intake and full roller cam.
Do you think this is too much carb for this motor ?

That carb is really too small for the combo and is simply out of tune if it's giving you problems.

The 950 is actually the same size as the the 750 with an 850 1-3/4" baseplate.

It's a numbers game started by Demon and Holley followed sute with the 950 but it actually flows about 820 cfm.

The 850/1000 is the biggest of the 4150's

That carb should work fine on there but it will hurt you a bit on the topend if your dragracing.

If you are drag racing then I would recomend an annular 850.

[Taman]

I have run Holley Hp's and standard double pumpers, Demon, BG Silver Claw, Edelbrock, and a Quick Fuel. I have gotten each carb to work. The Edelbrock made 30 hp less than a box stock Holley on the dyno. The Quick Fuel lets me idle at 1100 in neutral and 1000 rpm in gear. The throttle response is awesome.
I would find someone with a wide band o2 sensor. I have an Inovate that records and has a attachment to hook on the tail pipe so a bung is not needed. That will get the tune correct.

[TERMN8OR]

The Car is a street car only. Never see's the track at all. Right now its running really rich and my plugs are getting fouled up.
I was thinking the carb was just too big for my motor, as I don't track the car.
My fuel consumpsion is also awful. I know it's a big block, but I'm only getting around 4 MPG. I think I should be doing a little better then that ?
Do you think switching over to the Ultra Avenger 770 Vac Secondary rather then the double pumper will help ? Or do I just need to try and re-tune the carb..

[Taman]

You should be able to lean the carb out with smaller idle feed restrictors and put more air in with bigger low speed air bleeds. A smaller carb will give you better throttle response. I prefer Quick Fuel over Holley carbs. Nothing wrong with Holley, I just had better luck tuning the Quick Fuel. Ask your engine builder what they recomend. Call the tech line of whatever carb you choose. They will know the best.

[TERMN8OR]

I spoke with my engine builder today and he told me to go with the quick fuel ss-780-VS. Has anyone had any experience with this unit ?
It looks like a nice setup.