1969 GS 350 Q-Jet

I am new to this so a little slack please! I have a bone stock 69 GS 350. The Carb needs rebuilding or replacing. I checked the numbers and it is the stock carb.

My Q? What CFM was the stock carb on the 69 350 motor? I was thinking about a Stage 1 intake from TA performance (rest of motor will be kept stock) and they tell me to put a 750 CFM carb on the motor?

Any help? I just want a stock driver that runs great!

Thanks
Mark

 

While Rochester did not post actual CFM ratings for this carburetor, it is commonly referred to as a 750 CFM.

Be careful of comparing apples and oranges. While this carb and a 750 CFM square-bore have the same CFM at wide open throttle, the spread-bore design (quadrajet) is MUCH friendlier on the street; especially with an engine of 350 CID.

My suggestion: rebuild your original. Very easy carb to work on.

Jon.

 

YES ! !

I was very suprised when I did the simple math. Supposedly, a Q Jet has 150 CFM primaries and huge 600 CFM secondaries. a square bore 750 holley, like my 04779 has 750 / 2 = 375 CFM primaries!! Holy crap, no wonder the damn car is so touchy around town!! With the Q Jet, the car seems down on power, but the driveablity is great. The power comes in when you get the secondaries into play.

 

Andrew - if your power was down with the Q-Jet, it probably wanted some attention.

Secondary bog or hesitation is often caused by a fatigued airvalve spring. This is an item often overlooked, and should be replaced at any major overhaul of the carb.

Secondary power being off is often a function of the plastic cam that causes lifting of the secondary metering rods being worn. Another overlooked part that should be replaced at any major overhaul of the carb.

While some of the "Holley lovers" may disagree, the only area in which a 750 Holley should outperform a 750 Q-Jet is in professional road racing, or possibly off-road or marine use. Sometimes difficult to make the Q-Jet go around corners. It can be done, but it is difficult. On most street vehicles, the Q-Jet will have much better driveability, better fuel economy, and equivilent or better power.

Jon.

 

Thanks for the Info

I am shocked that it is a 750, I was thinking 600 - 650. My brother in-law has a new Edelbrock 600 in the box and tells me to try it. Again this is a STOCK 350!?! I just want a good driver that will go if it has to. Any comments on the TA Stage 1 intake?

Mark

 

Mark - unless you increase your airflow capacity greatly (wild cam, big headers, more compression, etc.), the other intake would be of little or no benefit. There is nothing wrong with a 350. A good tuneup, rebuild the stock carburetor, and enjoy. No, your 350 won't use all of the 750 CFM available, but that simply points out the flexibility of the spread-bore design. Small enough primary bores to support excellent low-end velocity, yet large enough secondaries to feed the engine sufficiently under wide-open throttle conditions.

Jon.