Tuning the quadrajet on our 1969 Impala
 

Hey guys, new to the forum but not to cars. We are in the gradual process of restoring a 1969 Chevy Impala Custom. Two door, hard vinyl top, 350 V8 (quadrajet four barrel) and a TH350 Tranny. 44000 original miles. Doesn't burn a drop of oil.

We have rebuilt the carb, put valve cover and intake manifold gaskets on it, had a new exhaust custom fabbed for it (true dual 2 1/4" setup with glasspack mufflers), and given it a good overall cleaning. It needs some body work and suspension work, but on the problem I'm asking is how the heck to get this quadrajet to run right.

The problems are, when I first start it on a cold startup, when I have to tap the gas to choke it, it runs extremely rich, 'lopes' like it has a cam and blares out black smoke. If I rev it up a few times it clears up and idles fast like it should. The other problem, is sometimes from a dead stop, or from say a 30 mph roll, I will put my foot to the floor, and it will totally hesitate, backfire, and then rev up.

Also, if I were to go WOT from a stop, it will wind through 1st gear, shift at about 4500 rpm, go halfway through second, and then just sputter like it has no more fuel.

Any ideas? If you guys don't know, do you know anywhere you'd suggest I look to find tuning help on this? Thanks!

George

RE: Tuning the quadrajet on our 1969 Impala
 

The Q-jet is a tricky beast... first with the cold start up, check and make sure the vacuum pull off is working. it opens the choke about 3/32 to 5/32 of an inch after the engine starts... as for the hesitation and backfire sounds like the accelerator pump is not working properly either a dried up or tornseal or clogged passage. now for the fuel starvation on WOT in second gear there are vacuum controlled primary needles that close off the fuel to the primary jets sometimes they stick down. or there is junk in the fuel passages. the only cure is a good rebuilding by someone that is good withQ-jet carbs. Ihope some of this is a help...

RE: Tuning the quadrajet on our 1969 Impala
 

Thanks, that does help. I mean when it's warmed up and you drive it gentle, it works smooth as silk. Just on the startup and anytime I like to give it heck.

Can you reccomend any books on the carb? Websites? Any sources? All my neighbors run Holley's on their cars and they are all race oriented cars. Not anyone to my knowledge around here knows anything about quadrajets. Most people tell me they suck and to buy a Holley. One guy I work with says they work excellent if you know how to set them up.

Thanks!

RE: Tuning the quadrajet on our 1969 Impala
 

they're both correct they do suck... and they do work excellent if you know how to set them up... however the only knowledge i have on them is years of handson workwith them. a good one like the one you have is hard to come by, but if you have one with serious problems it's hard to get them to work properly. it may be a problem with wear or warpage... witch I'm pretty sure yours has neither... more then likely it is because the last time that thing was apart was in 1969. 40 years is a long time for a Q-jet, I'm surprised it works as good as it does! if you want to keep the car original get that thing rebuilt. look around for some older Chevy car forum I'm sure there are people that know a lot more about where you can find books or websites or even a place to get it rebuilt.

http://www.superchevy.com/technical/...ild/index.html

this is a link to a super chevy site the company that rebuilds the q-jets that is featured in this article does a damn good job we have only used their 2bbl carbs for racing but they work well!

http://www.customcarbs.com/CarbShopContact.htm

http://www.thecarbshop.com/

a couple more i found doing a quick search!

RE: Tuning the quadrajet on our 1969 Impala
 

Hey thanks! Like I said my dad and I did a basic rebuild of seals and gaskets and such to it last year. I think it's really a tuning/adjustment issue.

The only 'problem' is the fuel nut on the fuel line going to the carb is a bit rough, but the carburetor itself looks almost mint. I ordered a choke pull off for it, found one on a carburetor website for $15 shipping included.

I will look into those sites and try to find some other forums.

The car isn't far from being in excellent condition. I'm going to get it running right, then drive right, then looking great.

Thanks again, God bless!

George