rochester q-jet tuning help

[monza-tc350]

hey guys i got a rochester q-jet out of a 83 trans am and i need help on how to tune it properly the carb number is 17083278 if that helps at all. if sombody could get me a guide that would be great

[gotmud7]

I would recommend the Rochester Quarajet book. I piocked it up a few years ago because it talked a little about the 2 bbl in my Vega. Try amazon.com for it.

[marco_1978_spyder]

Yep, I agree, get that book, its by Doug Roe.

There should be some helpful sites out there if you just plug "quadrajet tuning" into google

[monza-tc350]

ok i will keep an eye out for the book

[gotmud7]

You might evven want to try an autozone or advance auto. It's probably $19.99 They sometimes have a good book or two. I once heard it was discontinued, but I still see it in paarts catalogs.

[monza-tc350]

we have lordco or mopac in canada

[marco_1978_spyder]

I'm sure there's some Q jet experts here, who might be willing to help ... What engine is it going on, and what kind of driving will the car see? More track? More daily driving and cruising? The Q jet is great for a cruiser.

If it's going back on the engine it was made for, a stock rebuild kit should get it working great.

Its good that its off of a T/A. Better chances that you have the desireable rods, and hangers, than say if it came off of a Van or something

[monza-tc350]

its on my 262 and the car will be seeing allot of crusing

[cjbiagi]

I know the Q-jet on my 84 Monte SS had some electronic controls on it, does this carb have the same? Some of those need a computer to work right.

[marco_1978_spyder]

A Qjet from a 4.1 buick V6 would probably have the best rod/hanger combo for your 4.3 V8.

Did a later 267 V8 ever come with a Qjet??

[monza-tc350]

no the guy i bought the car from put an edllebrock performer and a rochester Q-jet on it they are suposed to have a 2bbl even the 350 monza's had a 2bbl

[Len]

Question ??? are you tuning for air care or are you tuning for performance ??
Len

[monza-tc350]

air scare

[ratio411]

I am not going to get into detail, mainly because I haven't worked on a Quadraflood in a great many years...
But I will give you a couple pointers...

1: Accel pump tuning... Like any other carb, the accel pump needs to be tuned such that it delivers fuel into the venturis at the slightest movement of the throttle.
If there is any delay at all, between the movement of the linkage and the squirting of fuel into the carb throat, there will be a bog or at very least soft throttle response.

2: A Quadrabog is not a typical mechanical secondary carb, nor is it a vacuum secondary. The Quadrajunk is a hybrid of the two designs.
The secondary throttle plates open mechanically with progressive linkage, just like a double pumper Holley. However, like the vacuum Holley, it has no accel pump shot upon the opening of the secondaries. It relies on the upper 'butterflies' to keep the secondaries out of play until the engine is TRULY ready for the extra air flow. There is a spring and weight system in the upper butterflies that keeps them closed until the engine reaches a point where it can open them itself as needed. This is where my 'tip' comes in.... This carb design is EXTREMELY sensitive to the adjustment of the upper butterflies. You want them adjusted just a bit on the tight side. If you have them adjusted to open too freely, the engine will pull them open before it is ready for the extra air, and create a bog. If you have ever heard of someone claiming they can "feel" the secondaries kicking in, what they are actually feeling is a bog created by the secondaries opening too soon. A properly adjusted secondary should NEVER be "felt". It should be a smooth transfer of the butterflies opening only when the engine has suffecient flow built up in the secondary circuit to both overcome the butterfly springs AND flow fuel through the secondary sytem. There is no second accel pump, so fuel/air MUST be moving within the secondary system when the butterflies open, or you just have a momentary vacuum leak, aka bog, until the engine gets the circuit flowing.

Make sense?
Sorry so wordy, but if you understand what is going on in full, it helps make carb tuning less of a mystery.

[Lespaul59]

When my 69 4-speed gto Judge secondaries open up , You hear the bog and it throws you back in your seat. So much for that assumption.You guys are just stuck with cars with low compression that's all.