quadrajet jets

[luxeryvic]

i have a quadrajet carb from a 77 chev pickup i was thinkin of changing the jets to jet it to flow more, what size of jets would you recommend if this is a good idea.

any other suggestions?

the carb is going onto either a 305 or a 350 witha summit cam SUM-K1102

[Fresno 126]

Hi I am not familary with the jet sizes in a quadrajet, i do know that most of the time it meet your modifyed needs in stock trim. If your cam has a big lift and duration i could maybe see the point, but if it is just one or two steps above stock, run the carb as is and see how she runs. Those carbs can flow quite a bit of fuel. As a note if you could help with this question i would appreciate it.

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[silicon212]

If you feel you need to ask, you need to take it to someone who knows.

Not trying to knock your skills, but there are so many variables - is it off a 305 or a 350? Is it going on a 305 or a 350? What jet sizes are on it now? Is it a computer feedback carb? What cylinder heads? What C/R? Stock or aftermarket exhaust? There are way too many variables.

Why do you want it richer? Just because of the cam? Is the cam streetable? There are too many factors here, sorry - I wish I could help more.

[luxeryvic]

sorry, im only 16 and have lots to learn lol

the cam specs are Basic Operating RPM Range:1,500-4,000Intake Duration at 050 inch Lift:204Exhaust Duration at 050 inch Lift:214Duration at 050 inch Lift:204 int./214 exh.Advertised Intake Duration:262Advertised Exhaust Duration:272Advertised Duration:262 int./272 exh.Intake Valve Lift with Factory Rocker Arm Ratio:0.420 in.Exhaust Valve Lift with Factory Rocker Arm Ratio:0.442 in.Valve Lift with Factory Rocker Arm Ratio:0.420 int./0.442 exh. liftLobe Separation (degrees):112the carb is off of a 350 going onto a 305
(but maybe a 350 if i can find one, could you recommend jets for both engines)

the heads are 354434 off of a 305 with a compression ratio of 8.5:1 if it goes on to a 305

i might use these heads on a 350 for a higher compression ratio

it is not a computer controlled carb
after market exhaust long tube headers through turbo mufflers

i want to match the carb to the cam for its full potential

hopefully all this info helps

[MrPbody]

Q-Jets only use "jets" in the primary. For improved performance at higher revs, the secondary metering rods need to be changed. Unles you're experiencing idle and off-idle problems, leave the primary side alone...

If the carb is a stock '77 unit, chances are the tips are in the .060" diameter range. There will be a two-letter code stamped into the metering rod. The "CC" and "AX" are the "richer" rods used, and are probably a bit much for the torque cam you describe. But a 305 with that cam will act more like a 350 with a cam with more duration. It MAY be that the AX rods (about .041" tip diameter) would be just right.

Also, setting the tension on the secondary air valve will make a HUGE difference in how the engine performs under wide open throttle. Trial-and-error is the best way to set that. Cliff's High Performance in Mt. Vernon, Ohio, sells a great "how to" Q-Jet book. he's a Pontiac guy, but don't let that fool you. He has NHRA SS customers that run Q-Jets deep into the 9s.

Jim

[comp]

I agree you need to get the books and read up