["Guy]

Hey Cliff, I'm trying to build the perfect carb or close to it...What do you think of:
Top plate of a '68 wt carb.
body of a 850cfm '76 carb.
bottom plate of a 68 wt carb.
acc. pump cut to get the pump shot.
trimmed throttle blades for more cfm.
.149 needle and seat.
small(est) float and trim 1/4" of bottom of float holder.
and do you have a p/n for the smallest float that will work in this carb body?
I don't have the number on the body but I will get it if this helps.
Thank you,
Guy

["Guy]

Hey Cliff, I'm trying to build the perfect carb or close to it...What do you think of:
Top plate of a '68 wt carb.
body of a 850cfm '76 carb.
bottom plate of a 68 wt carb.
acc. pump cut to get the pump shot.
trimmed throttle blades for more cfm.
.149 needle and seat.
small(est) float and trim 1/4" of bottom of float holder.
and do you have a p/n for the smallest float that will work in this carb body?
I don't have the number on the body but I will get it if this helps.
Thank you,
Guy

["Guy]

Cliff,
I meant trimmed throttle shafts..
by the way this Qjet

[Cliff R]

Sorry, the parts will not interchange. You can us an early 70's Buick carb with the larger main bores (800cfm). They can be disguished as Pontiac carbs, I've built a few here for "special" applications. They are about as good as it gets for having an big cfm early style carb.....Cliff

["Guy]

Cliff, do you have one of those Buick bodies you want to get rid of? Or can you tell me what Buick they came off of? Weekly's auto wrecking in Grand Forks has lots of good old stuff...Talk to Scott Weekly if you need anything. I would like to talk to you about a smaller float set-up/opening up bowl area for more volume for the Qjet set-up I have now, and build that Pontiac/Buick carb soon.
Thank you,
Guy

[Kenth]

Try to find a 1971-74 Buick 455 Q-jet (800cfm) and swap the throttle plate only.

You cannot swap carb tops unless you modify the idle air system in either body or top to match eachothers system.
Pontiac Q-jets uses idle air from the carb top, and Buick Q-jets uses idle air located in the floatbowl.

[Cliff R]

There is another problem encountered with using a non Buick baseplate. Most of the early 70's Buick q-jets use the early style APT. This is a really nice feature and allows for external adjustment of the primary metering rod height in the jets. These carbs will have an aluminum plug in the baseplabe between the mixture screws and a steel post on the bottom of the power piston. It is best to retain the original system.

The 1976 and later front inlet q-jets have the smaller float and later APT design. They are excellent starting points for a really nice carb. There is really very little if any advantage to hogging out the fuel bowl for increased volume. I've done enough dyno and dragstrip testing at this point to know that the fuel system has to be able to keep the carb full on hard runs. Adding more bowl volume is not a bad idea, but will only allow a slight bit more reserve, the real fix is to have a fuel system capable of keeping up.....Cliff

["Guy]

Did Weber use Buicks design to make the Qjet 850 RPM Edlebrock carb? I will pick up that small float for my '68 wt pontiac carb. And when I get to G.F.,No.Dak. I'll pick up a '76 buick 455 carb to play with. My Fuel system that i'm trying this time is all Stainless steel 3/8 including the pick-up I re-did instead of the stock 5/16, Carter strip pump(mechanical), Napa canister filter with a 1/4" vapor return hooked to my return line from the tank, this installed before the mechanical pump, Areo equiped 3/8" line from mechanical pump to carb. If all fails and she falls on her face still then I'll run a electic pusher pump...and if it fails I guess its time to sump the tank....Qjet carb #17054905..what did this come off of?

[Kenth]

#17054905 is a Delco 1968-69 service replacement carb for 350-400-428 Pontiac with 1968 and earlier float style, #73 jets, #41 pri rods, sec rods stamped BE.
You can start with this jetting in the Buick body when using the Pontiac throttle plate, wich as said before, lacking the early style APT.
Just make sure sizes of the main airbleeds are somewhere in the neighborhood.

It is of course possible to use the complete Buick carb too, and rejet/modify it for your needs.

[Cliff R]

The Edelbrock "850" cfm carb is the late style single main airbleed side inlet Chevy design. They are no different in dimensions than any of the 1976 and later front inlet q-jets. They would flow no more air in any configuration than say a well prepared 1977 Pontiac q-jet. I've actually tested the Edelbrock "850" at the track on back to back runs against my own q-jet. It ran within .02 seconds at almost the exact same mph.....Cliff

["Guy]

Cliff...the rpm qjet carb must like our ponchos.
Did you dail it in or just slap it down and run? The apt just make it easier to get the tapperd part of primary rods in the correct position right? When I say easy...I'm thinking nightmare! Getting the rod height in the main jet hole right and getting the right power piston spring can make the difference in a great running motor. How forgiving is the apt?

[Cliff R]

The RPM q-jet was carefully recalibrated and prior to testing. The APT can be used to fine tune part throttle mixtures, it is a really nice feature. The power piston spring(s) are not really much of a factor when tuning a q-jet. Use the strongest spring that will have the power piston stay down at idle....Cliff