[bpc]

I looking into a new carb for my combo....

461 stroker
ported 62 heads opened to 88cc flow aprox 240
comp ext284 cam
rpm intake
2800 stall
355 gears

Would I require a
800 cfm single or dubble pump or
850 single or dubble pump..

Finaly quadrajet 800cfm or higher...

Thanks so much...

[steve25]

Dependant on the intake manifold, if the Q-jet will bolt on without a adapter that would be my first pick, second would be the 850 DP.

[chiphead]

What car, weight, street/strip, race only, what???

RPM intake, huh? If it's driven on the street, then Q-jet hands down. IMHO one runs a RPM intake when you care about throttle response and street manners but still want top-end charge to 6100 RPM. For that, the Q-jet rules.

850 double pumper would maybe be better for strip duty, but also better suited for single plane intake and give up on the street manners and gas mileage.

Some say that they like running a big carb and single plane intake on engines larger than a 428, because it kills some low-end torque that breaks tires loose at the dragstrip. Shifts the powerband upwards. Since I run a 400, I try to build on the low and midrange power by using a RPM and Q-jet.

[Indian Uprising]

I have a similar combo and use a 750 cfm speed demon, car runs great. Although it would prob prefer an 850.

Barry Grant Tech watches this forum. Maybe He can chime in..... Also feel free to give them a call.. they have excellent tech support and can make a recommendation for you. I have called them several times and they have helped me out.

I copied their contact info from thier webpage:
tech-sales@barrygrant.com
Phone: (706) 864-8544
Fax: (706) 864-2206

[Jeff Walker]

For street/strip use a properly set up Quadrajet is hard to beat IMO.

[Mr. P-Body]

With the exception of the intake, we build many engines of that combo. The AED 850HO seems to be the best one for the job.

While I agree the Q-Jet is an excellent carb, the low-end would be BRUTAL in this build. The Holley might "soften" it a bit. As Jeff said, for a primarily "street" application, Q-Jet is the better choice.

Jim

[DiamondJim]

QJ or 850 DP, this might be of interest. http://www.sdperformance.com/newsStory.php?newsID=44 -Jim

[shaker455]

A custom built annular 850 would fit well.

[gumbys goat]

I had a750 on my setup similiar to yours except I have the E heads,and it was a snail,Then I called cliff and he made me up an 850 and Holy crap what a difference,that made.

[Cliff R]

The long stroke Pontiac engines enjoy big carburetors. They probably don't need the total cfm capacity, but right on the dyno we've lost 10hp/12ft lbs going from an 850cfm carb back to a 750cfm carb on back to back pulls. The engine was a 455 with E-heads making around 505hp/551tq.

Without exception any and all testing we've done with dual plane intakes, iron, HO, RPM have favored the Q-jet spread bore design.

As a general rule, single plane intakes give up some power when a Q-jet is bolted directly to them.

Here's my opinion of what's going on here.

A dual plane intake has a really wide plenum area on each side,and a divider between both sides. A spread bore carburetor is aligned very well with these plenum areas, or well centered in each of them. The incoming air doesn't have to make to many turns, or change angle nearly as much as a square flange carburetor sitting on the same intake. Without exception, all back to back testing we've done between Holley style carburetors and q-jets have favored the q-jet by a couple of HP and a few ft lbs torque.

Completely different deal with a single plane intake. They are designed for square flange carburetors, so favor them for power production. We have observed some pretty significant power loss bolting a q-jet directly to a single plane intake. I'm certain that the large diameter of the secondary throttle plates extend too deep into the plenum area(s) of these intakes. This causes the incoming air provided by the secondary side of the carburetor to have to make some pretty sharp turns to enter the ports, and, the air in on a different plane than the air coming from the small primaries. This may cause some additional turbulence, or at least the air has to do some additional movements to get to all the runners.

I say this because as soon as we add a 1" or taller spacer, all the power comes right back, and the q-jet will make within a couple of HP of a square flange carburetor on the same single plane intake.

As for dyno testing, and specifically in reference to Dave's dyno testing noted above. Anytime you want the highest peak power numbers for bragging rights, get a T-II intake. Even on my own engine it made quite a bit MORE peak power than the iron or RPM intakes, but was DOWN considerably on power below apprx 4400rpm's.

Even when we ran the ill fated Comp solid lifter cam a few years ago back to back against the Crower 60919 cam, the numbers were WAY off until we tested a T-II intake. We immediately raised the peak power by over 20hp, but the engine still made quite a bit LESS average power, with a significant loss of power below about 4400rpm's.

Since we are in the street section, giving up power down low will most often SLOW your car down, even if you make a stronger top end charge.

Case in point. We tested the Tomahawk manifold a few years ago at an HPP Shootout, back to back against our iron intake. It immediately picked up almost 2mph and ran the fastest for all runs that day. This shows that my engine really like the intake, and it no doubt made the most top end power, or peak HP. Even so, the iron intake provided the quickest ET by apprx .02 seconds, as the single plane intake gave up nearly a tenth in 60'.

Basically, do NOT be confused by dyno numbers, the highest peak numbers do not always produce the best vehicle performance. ET and MPH are far more dependant on the total combination of parts, as few street cars leave all that high in the rpm range and stay up near the shift point for most of the run......Cliff

[Tech @ BG]

In our carb offerings we would go with the 800 but it will flow more then an out of the box style 800. Our 850 will be just a tad on the big side and you may give up a little bit of bottom end in exchange for a stronger mid range and top end charge. Either way with a 4150 style carburetor stay with an annular booster version for the application listed.

[Tech @ BG]

Originally Posted by Indian Uprising

I have a similar combo and use a 750 cfm speed demon, car runs great. Although it would prob prefer an 850.

Barry Grant Tech watches this forum. Maybe He can chime in..... Also feel free to give them a call.. they have excellent tech support and can make a recommendation for you. I have called them several times and they have helped me out.

I copied their contact info from thier webpage:
tech-sales@barrygrant.com
Phone: (706) 864-8544
Fax: (706) 864-2206

Thanks. Yeah the 750 is a little small but as long as it runs and drives good for you that is all that matters. You would see a performance gain by going to a larger carburetor just because the Pontiac stuff seems to like them but then again no need to change it if you are happy with it.

[MandevilleBird]

I went with Mr. P-body's suggestion and spoke to John Dickey @ AED(804-271-6076). Great guy! I went with his reccomendation and am happy. He even called me one Saturday to follow up...

For my particular set-up, he reccomended their 950HO. It really woke up my engine! Give him a call.

Just my 2 cents worth...