I've got an 83 Z28 5.0L HO 4bbl. I hear all kinds of talk about the qjet carbs, but they are all 81's and below. Is there anything on the 83-86's? Any help would be great.

 

What kind of talk do you want? Is there a specific question(s) you have?

The secondaries are the same on either type. There is no power valve on the CCC carbs, only a rich stop adjustment. There aren't a lot of differences.

 

The only real difference in the CCC Q-Jet made in the 80s is the fact that GM controlled the PART THROTTLE A/F mixture in order to clean up the emissions. That combined with computer timing control actually boosted the MPG of the cars somewhat.

 

Doug roe's Guide to Quadrejets, is more or less the bible on them :-)

Grab a copy , read up and tweak away.

All your hanger combos and metering rods are only a junkyard walk away.

I love QJ's, I love EFI too, but still cuss at my friends I'm gonna throw all that crap away and do a LS series swap with a QJ on top lol

later
Jeremy

 

My back up carb (a Rochester Quadra jet) came off a /74 GMC truck that had a 454 in it. The thing I like best about the old Rochester’s is they came with a divorced type Choke. The divorced type choke can be easily modified to become a manual type choke, just drill a pin-sized hole into the choke linkage and remove the left over choke parts. Much easier than converting the newer style choke’s and works better too.

The other thing is the older Rochester’s (and Carter’s as well) where designed from the factory with adjustable fuel air mixture screws. They look a lot better after you rebuild them, as you don’t have the broken corners with those ugly square screws. Also, if you use a Rochester off an older Truck you may end up with the larger CFM, larger jets etc.

If you choose the Edelbrock Performer Air Gap (idle –5500 rpm) you can still have the option of using a Quadra Jet. Unlike the RPM series that would require an adaptor plate.

I have also found large CFM Quadra Jets on Chrysler big blocks, but required some accelerator linkage modification to work on my S.B.C.

 

Ford used large CFM QuadraJets from Ford.

Edelbrock makes a Spreadbore RPM intake, I have one.

 

I assumed Ford would have them as well, but I only had one ford and I traded it for a case of beer.

The manifold I was referring to is the Air Gap series

I only know of the two Edelbrock Air Gap Manifolds:

1st the Performer Air Gap (idle –5500) both square bore and spread bore part # 2601 also comes in polished or Vortec.

Or

The Performer RPM Air Gap (1500-6500) that will only accept square bore carbs part #7501 (will not take a spread bore carb)also comes in polished and Vortec as well.

Do you have a part # for a Peformer RPM Air Gap that will take both a square bore and a spread bore?

 

I was talking about the standard Performer RPM, not the air-gap. IMHO, the air-gap is not the best streetable manifold, the RPM works great though, even in cooler weather.

 

IMHO ?
The Air Gap is very streetable, I know because I run one. Not sure what kind of cold temps ya’ll get down there it Texas, but up here in Canada with temps of zero degrees Fahrenheit the Performer spread bore Air Gap works fine.

With an O.E.M motor and O.E.M. torque converter the Performer is a better choice. Why use a 1500-6500 RPM manifold on a motor that has a max RPM of 5500? and a stock torque cnverter?

 

You must be about the only one that has any luck with the Air Gap and cooler weather. I had trouble with mine in the 20s. A/F would not vaporize correctly, carboned up my pistons, fouled my plugs, etc. The lack of a heated plenum floor also raised my HC emissions enough to cause me to fail the dyno smog test. I lost NO HP in even 105*F ambient temperatures by going to the Performer RPM non-air gap. I am running TBI, BTW.

The RPM outperformed a standard performer throughout the WHOLE powerband on a stock 305 chevy. It pulls much harder in the upper rpm band but does not give up ANY low-speed torque to speak of. The performer series=stock replacement, IMHO.

 

Still have no idea what IMHO means? And I have no idea how an Air Gap will work with a computer controlled T.B.I. set up. The carb recommendation, and later the manifold recommendation are/where to help the guy with the, “ /83 Z28 5.0L H.O.” Which is not a T.B.I.

For a stock 5.0L none T.B.I. car, I still think the best choice would be a Manual choke carb on a Performer Air Gap (idel-5500 RPM). If one chooses to use a spread bore carb I recommended the Rochester / Carter divorced type choke as they can be easily modified to manual choke.

The Air Gap has no EGR, and may not be the best choice in regard to emissions. But if the post was an emissions question, the best answer would have been fuel injection anyway.

A tuned H.E.I, with a none computer controlled carb, with a manual choke, on a Performer Air Gap would be the best choice on an older stock motor, with a stock stall torque converter. Remove the clutter, clean up the engine bay, and chances are the emissions will be better with all that 26-year-old worn out emissions system anyway.

 

"In My Humble Opinion".


(Let's keep the dialogue civil, please.)

 

TBI & Carb=roughly the same as far as manifold choices go. I have run a performer RPM spreadbore as well as squarebore. The spreadbore was run with a Q-Jet and TBI. The squarebore was run with a 1406 Edelbrock and a 670 Street Avenger. They both ran very hard. The air-gap got sold on Ebay after unsucessful results on both carb and TBI.

I don't know about the F-body and the AirGap fitting with a decent air cleaner and the stock hood though? It just barely tucked under my stock doghouse, which probably has more room than a stock F-body hood, (I can fit a 142 mini blower with no clearance issues).

I use IMHO as In My Honest Opinon some do Honest some Humble.

 

IMHO oh, I see.

Other than the cold climate issues, can you please give details on what running problems (Performance Issues) you had with your Air Gap.

 

I never really had any performance issues with one, just that it didn't like to stay running as the choke pulled off or the coolant temp came up on the TBI which caused it to start leaning out. If I kept it rich enough to run good and have good response, it killed my fuel mileage. If I leaned it out to keep my mileage, it would stumble, pop, backfire, etc on tip-in. The RPM has virtually the same performance (like within 5HP) and has NO cold natured tendencies due to the exhaust crossover in it. The best solution I could come up with was a stock heated air cleaner and it was marginal at best.

Grab a carb on a cool engine on a cool day that has just been started. It maybe 50* outside, but the carb will be freezing as in ICE on it. That is with the stock exhaust crossover. Now imagine taking the heat crossover out, isolating the carb and runners from nearly all engine heat with the air-gap, then take and put an open element on it. Dense air/fuel mixtures are of NO benifit, IF you can't keep the air/fuel mixture atomized and vaporized. The carb introduces the fuel as an atomized mist, and the intake, intake valve, and combustion chamber has to vaporize the fuel in order for it to burn. More liquid fuel=less power, less fuel mileage, dirtier emissions and more carbon build-up in the engine

 

My new motor (a 290hp/350 crate motor) has never run with anything other than my Performer Air Gap. It took me a long time to get it running good, (my own oversights) but it seems to be running quite well now, she starts fine, idles fine, but it does take a few extra minutes to warm it up (no big deal).

I am now quite interested in how it would run with an Edelbrock RPM (none Air Gap). I think once the weather warms up I will through one on just for fun to see the different for myself. I will be surprised if I get a better snap out of the hole, seeing as my motor is very mild, and my cam maxis out at 5500RPM. The stall speed on my converter is quite low also, but I enjoy messing around and trying different things on it, so I figure what the hell, I can always through the Air Gap back on.

Did you notice any differences in Manifold Vacuum between your Air Gap and you current RPM? Do you have the Vacuum numbers from both manifolds?