[Dauntless1971]

I have a early 75 California smog version Rochester now. It needs an overhaul. From what I read the early 75 version is not as easy to tune as later ones. I will be using a 200r4 transmission. So I am considering getting a different carb also since my engine came without the needed air cleaner to use. I see there is bracket available to bolt on for the cable that fits some carburetors.
As I read up on the Rochester carburetor most of the print says up to 1979 being the best overall, aka not racing that is. Starting in 1981 many carburetors were fitted for the tv cable of the 200r4. So my question is could a early 80's Rochester off a 307? be set up to run correctly on 300-325 horsepower 400 Pontiac?

[25stevem]

I would say 69 to 78 and then next big consideration for me would be that the base plate has been rebuilt with replacement bushings.

[Formulabruce]

Best carb for street build ( and Cliff says in his book) is the 77-79 q-jets . I run a 78 with a bolt on bracket for the TV cable. The TV bracket basically will take the place of the th350 kick down if you have a auto throttle bracket. I run an adjustable TV cable and my carb is from an automatic. It is 800 CFM. has APT ( which really helps with idle and off idle mixtures with the alcohol fuel. I have run a 78 Olds carb as well. If you are not number crunching, you will be very happy with this.

[77 Canamman]

You do not want a car Q-Jet from 1981 and newer. These were the Computer Command Control units with the mixture control solenoid, and throttle position sensor. You can possibly adapt the throttle body to an older carb, or use the throttle levers form a newer CCC unit on a old throttle body.

[gtokid1968]

Can't remember the number off the top of my head but it is from a 77 Grand Prix 400CID
I bought one off flebay,
I bought a kit from Cliff, and he told me what 2 small holes to drill out based on my 406cid engine.
That is the carb Cliff used on his Ventura for all his testing.

[Dauntless1971]

I was reading up on another forum about using the throttle shaft and linkage bracket from the early 80's on pre 80's quadrajet and at least one person did this successfully. It was also noting that some early 80's quadrajets came in the non CCC version. And that Rochester limited the secondaries to just 70 percent opening.

Originally Posted by 77 Canamman

You do not want a car Q-Jet from 1981 and newer. These were the Computer Command Control units with the mixture control solenoid, and throttle position sensor. You can possibly adapt the throttle body to an older carb, or use the throttle levers form a newer CCC unit on a old throttle body.

[Kenth]

A geat deal of 1981 and later Truck Quadrajets are non-CCC and are as good as any 800 cfm candidates for a performance unit.

[77 Canamman]

Notice I said the word "car" in my previous post...

You have to be careful with some of the mid 80's truck carbs, as they are a bit of a hybrid. They have a TPS for the ESC, but do not have a MC solenoid. It is very easy to snap off the little tit from that TPS if you aren't careful.

[mzbk2l]

Originally Posted by Kenth

A geat deal of 1981 and later Truck Quadrajets are non-CCC and are as good as any 800 cfm candidates for a performance unit.

I stockpiled a bunch of 17083223 and 224 truck carbs for later builds. I'm running one as-is on my '67 Cutlass and I've not yet had anyone point out that it's not a correct year - they just notice I still have a q-jet.

[nUcLeArEnVoY]

Any late 70's Pontiac carb with APT is good because their ease of modification, if need be. Reason for this is because they don't have huge main air bleeds that make them lean no matter how much you enrichen the various circuits. This is a big issue with the truck carbs. And they used the smaller nitrophyl floats and so they're not as prone to fuel starvation at WOT. If you can get your hands on a W72 carb, those are among the best.

[77 Canamman]

I agree with the above post. My '77 W72 runs superb through all RPM's, idles smooth, and starts well even after sitting for weeks, and also heat soak conditions. I went through it about 6.5 years ago, and jetted it richer, and followed Cliff's recommendations using his book. I have only used non ethanol fuel in it the entire time I have owned it.

[77 TRASHCAN]

The electronic Q-Jets are easy to spot. They have electrical plug ins on the top front of the carb.

These 76 Q-Jets are NOT desirable. They have 3 primary rods, one has emission or idle usage, that I know nothing about. I bought one by mistake because it had a hot air choke (it was an Olds carb). It was very grungy, and had noticed it as I was walking out of a self service yard. It did NOT have the silver plug like the later "desired" carbs do, the plug is on top, front and center. Under the

I assume none of the 3 rod carbs have the APT plug on top, Keith?

I can see why uses the 17057274 carb. They flat work well!!!

Cliff can supply ANY parts you need. A member here can build it for you. His username is Shaker455.

These good carbs are still around, but getting scarce.

I wonder which side inlet units are compatible to these desirable BOP units?

[Cliff R]

Couple of things to clear up.

1979-up Chevy truck carburetors are single Main Air Bleed models, not large MAB.

Several part numbers made in 1977-78 for truck applications are also single MAB but divorced choke models, and they are EXCELLENT units if you have a Chevy divorced choke set-up and needing one for high performance work.

They will all be non-CCC unless they were headed for California after 1980.

The size of the float isn't a player with sucking bowl dry on hard runs or any power level. With all Q-jets you are feeding the entire engine thru one needle/seat assembly. Unless you source out a high flow needle/seat assembly rebuild kits will NOT have on in it, so you are shot down before you get started. I put the high flow N/S assemblies in all my kits, if you want larger ones they are an upgrade at no additional charge. Standard is .135", options are .140", .145", and .149".

I recommend to run at least a .135" for all "high performance" applications. When you get to about 450hp and up you may need to go bigger, or upgrade fuel delivery or both. Even so a Q-jet can EASILY support big HP if you take the steps to keep them full. At this point I'd also recommend to stay off the Forums and Youtube for advice on fuel pressure (and other things including using a Q-jet for high performance work. A high percentage of the videos I've tried to watch and threads the "guru's" are giving advice on contain old/outdated/inaccurate information, so tread softly with some of the resources out there when it comes to this topic. Early models (and Olds/Caddy to 1974 plus all Marine) have a poorly located hinge pin for the float. They required a large float and still can suffer flooding issues with higher fuel pressure. Later models are NOT in that catagory and you can run high fuel pressure and high volume fuel pumps w/o issues.

Anyhow, the Chevy Truck carburetors made in and after 1979 are EXCELLENT units. They have all the latest features needed to build a really nice high performance carb. Edelbrock patterned their "850" cfm model 1910's from 1980 SMAB truck carburetors, part numbers 17080212 adnd 17080213. All they did was install huge idle tubes, a Marine length accl pump, .149" N/S assembly and increase the full open angle of the secondary throttle plates. They are also front pull-off models (prefered over rear pull-offs) so easier to modify for a quicker opening rate.

All are either hot-air or already electric choke, and they have APT for fine control of the part throttle A/F.

1976-79 Pontiac 350 and 400 carbs are also excellent units (the 301 carbs can be equally as good with some addtional effort) and as good as or even better than the later SMAB truck carbs, IMHO. However they have a HUGE front vent tube to deal with so plan accordingly. Their Oldsmobile counterparts are twins to them and have the standard front vent location so equally as good everyplace once correctly set-up and you don't have to poke a hole thru the air cleaner base and worry about how you are going to keep it sealed up.

For more info there is a chapter in my book on carburetor selection. The chapter on how they work also explains the SMAB vs other models that were made thru the years of production.......

https://cliffshighperformance.com/pr...et-carburetors

[redhawk44]

Thanks for the info Cliff, I have been looking but was guessing at the right numbers.

[tom s]

FYI,Bowtie overdrives wanted the throttle shaft changed on a fresh restored 76 TA carb.Something about the linkage.Tom

[locomotivebreath]

Cliff , what amount of fuel pressure will the early units take ?

[Cliff R]

The Q-jets with the short hinge pin will be fine with about 5-6 psi using a .135" fuel inlet seat. You MUST use the large factory float, both variety of brass floats made for them are WAY too small for effective fuel control with larger fuel in let seats.

You can get away with a little more fuel pressure and flow with the early units if you use an electric fuel pump and bypass system. Hammering on them with a high flow mechanical fuel pump w/o a bypass can be a lesson in humity.

Those early units gave Q-jets a BAD reputation as a good street/strip performance carburetor and the main reason was the poor leverage the float has on the fuel inlet needle.......