Jna_1991

So I am planing to rebuild and hopefully improve upon the 1981 Quadrajet. I have done quite a bit of research and so far my plans are: 1. Drill out air bleed screws to 3/32. 2. Drill out the idle down tubes to .034 and discharge holes in the lid to 0.29. 3. Switch to perforated tubes. 4. Open up choke pull-off diaphragm restrictor to .016. 5. Look for perforated tubes. 6. Go one size down on secondary rods (mine are ch now, so maybe CK or something similar?) 7. Lightly mill surfaces to ensure a flush fit. 8. epoxy the wells. 9. fiddle with all the other adjustments until i get a perfect as possible 14:1 ratio at idle. (power spring, primary rods/jets, rich and lean mixture screws.(I know that I need a dwell meter). 10. Replace bushings in the base plate. 11. If I am feeling really ambitious I will polish all inside the wells and primary's with a dremel.

So basically I would like to know from people with more experience then me if this sounds right before I ruin my carb or if there is anything I should add. Thanks for your time.

JayRay

I have been studying these Qjets a lot lately but have yet to see anything with drilling. From what I understand you can bend the needles to deliver more fuel without the need to drill them.

What is your end goal? The Qjet will deliver up to 750cfm on its own if your engine desires it. Most 350's will not even use all of it. Not sure what your engine spec is though.

Big2Bird

Your still talking a stock E4ME? With mixture control solenoid?

Jna_1991

Jayray I got the info from an article on SMI the idea behind drilling what the first two things I mentioned is it will open up the idle circuit for more flow fuel and air flow no necessarily CFM. What I understand is that will help with the transition to WOT. I am not sure of this because I know very little. But I would think there is some in between spot where power is transitioning and the flow will help there also. I guess I also want it to be ready for my future 383 dreams lol.

Jna_1991

Yes Big2Bird its the stock computer controlled carb.

Jna_1991

JayRay here is that article. I hope its not against any rules to link things. http://www.hotrod.com/articles/ccrp-...retor-rebuild/

Big2Bird

I wouldn't do any of those BS mods. A stock unit works just fine with the ECM. Playing with those secondaries will just make it bog. IMHO.

Antz81

Best person to talk to about this would be a1sensei. Not sure if he's still here though.

GUSTO14

You could also send a PM to Lars, he is without a doubt a Forum, Quadrajet guru and would give your plan a sanity check for you.
https://www.corvetteforum.com/forums...2251-lars.html

Good luck... GUSTO

Big2Bird

Last time I talked to him, his car was stolen/totaled. Maybe 5 years ago?

Antz81

lars doesn't work with the E4ME quadrajets, but may still have some ideas.

Yes, very sad. I just checked his profile, and he was last on earlier this year.

JayRay

You might also pick up a used carb, they arent but $40-$50 to experiment on, that way if you mess it up you will still have your origional carb to put back on.

Jna_1991

Thanks guys for all your advice. I will pm lars before I do anything. I am sure he can advise me as what I want to do is almost all the same as I would do to a non cc carb. Then once I decide on what to do ill post about it and how it works out.

7T1vette

Making all of those orifice changes would certainly screw up the calibration of the electronic carb. If you want the CCC system to work as intended, just rebuild the carb back to stock specs and replace the electronic fuel module in the carb. The computer will regulate the fuel/air flow to be correct with whatever engine configuration you have.

Big2Bird

The what?

Antz81

I think he means the solenoid

7T1vette

OK...Fuel Mixture Control Solenoid. Is that better?

Kid Vette

I have a1sensei's differential in my Vette. He ended up parting it out after it was stolen.

David Mc

After had rebuilt over 100 of those carbs, I think modifying the passageways would make it difficult to tune. It would render the factory tools for setting the mixture stops useless.

Jna_1991

Well I message Lars and this is what he said.

"Don't over-complicate it. Bump the jetting up 2 sizes and richen up the secondaries to the DA rods (the CKs are not enough of a change from the CH rods to make any noticable difference). Raise float level to .300. Open up the idle down to .039 and call it good - it will run well."

I cannot get the computer switch between open/closed loop no matter how much I drive it or heat it up. I think the TPS and o2 sensor are bad. Cant afford to throw parts at it right now. I might just stay with the non-cc carb for now and hold on to the CC for later. I will try to go with what Lars said on one of my extra carbs I have a non-cc off a 81-86. Not sure what its off of as carb id say its a 283 and that doesn't make any sense for 81-86. Either way ill post back with the results of whatever mods I do. Thanks everybody for all your input on this topic!