Rochester carb jetting?

Discussion in 'The Venerable Q-Jet' started by 69gs400, Mar 20, 2024.

  1. 69gs400

    69gs400 Well-Known Member

    Hey all, looking for a little guidance. The original carb for my '68 Riv is currently being rebuilt. At the same time I'm building a new engine. Engine is a .030 over 455 with TA forged production pistons, notched version advertised at 10:1. Block has been decked .010 and the same taken off the factory iron heads, Felpro head gaskets. Cam is a TA 290-94H , 287/303 and 514/530 at 1.60 according to the cam card but I'll be running 1.55 rockers for now. Edelbrock Performer and shorty headers.

    Do you think I'll be okay with the stock jetting? Is this even something that can be figured out based on the info above?
  2. knucklebusted

    knucklebusted Well-Known Member

    Edelbrocks will generally run on about anything, but they are often on the rich side. With headers and cam, you'll probably be close enough to enjoy it but tuning it would make it better.
  3. 436'd Skylark

    436'd Skylark Sweet Fancy Moses!!!!!

    You'll need to re-jet the carb. The 430 carb will be too lean. I believe the 430 will have 71 jets and the 455s used 75s. I cant remember the rods though, which might make them net closer. You'll need to do some work.
  4. 69gs400

    69gs400 Well-Known Member

    Rochester carb, original to the 430. Edelbrock intake.
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    So 1968 Q-jet for a 430? 7028240? Stock jetting is .070 jets and 43B primary rods. BG secondary rods.

    Rule of thumb is if you go up over 3 primary jet sizes, go up one rod size.

    Or, you could send the carburetor over to Ken Gies (techg8) and let him jet it for you.

  6. 69gs400

    69gs400 Well-Known Member

    Thanks for that, do you by chance have that same chart for a 70 455?
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member


  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  9. 69gs400

    69gs400 Well-Known Member

    Thanks, I do have the chassis manuals, didn't even think to look for carb specs.

    I am confused though, based on those charts it looks like the '68 430 had bigger jets than even the '70 Stage 1.
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    There is A LOT more to carburetor calibrations than jets and rods. There are air bleeds and restrictions that play into it. The Quadrajet was individually calibrated for the exact engine it was designed for. That is why you can't just throw ANY Quadrajet on ANY engine and expect it to perform perfectly. That's why the Quadrajet is maligned the way it is. You can't compare 2 Quadrajets like that.

    Read Cliff Ruggle's book if you want to play with them.

    Or, send your carburetor to Ken Gies (techg8) and ask him to calibrate it for your application.
    Lucy Fair and 69gs400 like this.
  11. Canadian GS 350

    Canadian GS 350 Well-Known Member

    If the carb is unmolested, just up one size on the primary jet with the stock primary rods. On the secondary side, make sure choke pull off is not releasing too quickly, have some tension on the air door. I used to run richer rods on the secondary because more fuel must be better? Not always so. A good place to start is a set of CV’s. They have 0.053 tips. Good luck. When Qjet is set up well, they sure perform great. Get your distributor set up to complement your combo as well. You’ll be glad you did.
    69gs400 likes this.

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