350 vs. 340 exhaust manifold layout

Discussion in 'Small Block Tech' started by Dano, Mar 8, 2021.

  1. Dano

    Dano Platinum Level Contributor

    Are the exhaust bolt patterns &/or port layout the same on a 350 vs. 340?

    I saw a place that sold shorty headers for 340's and was wondering if they'd fit or could be modified for a 350 unless someone makes them for 350's, which I've never seen.
  2. Jim Nichols

    Jim Nichols Well-Known Member

    Nope, 300 and 340 have the same port layout as the 215 and Rover.
    philbquick likes this.
  3. Dano

    Dano Platinum Level Contributor

  4. sean Buick 76

    sean Buick 76 Buick Nut

    I do have 10 sets of 350 flanges so if a person wanted to they could buy a set of Chevy short headers to modify to fit the buick flanges.
  5. Dano

    Dano Platinum Level Contributor

    Thanks - May take you up on that offer. Was going to post at some point as my builds get closer to see if there would be any interest in 350 shorty headers. I don't know if the performance gain would be worth it but not sure that I want to run long tube headers (does this mean I'm getting old, lol?). Also been thinking about building one of my GS 350's as a stock appearing (F.A.S.T.) 350 car as well and seeing what could be done there with respect to performance.
  6. Jim Nichols

    Jim Nichols Well-Known Member

  7. 12lives

    12lives If it runs, it's done!

    TA has them: http://www.taperformance.com/products.asp?cat=385

    Not shorty's though, but I don't believe there is much gain in shorty's over stock.

    Also, I don't think FAST rules allow headers:

    "4.01 Cast iron exhaust manifolds are mandatory and must be correct*, have correct* casting numbers and be of correct* material.

    Under no circumstances will headers be allowed, including those cars that had headers delivered in the trunk.

    Internal modifications are OK. Correct* appearing exhaust manifold paint or coatings are OK. Casting date codes are not looked at and are not part of the tech process."
    Last edited: Mar 9, 2021
  8. 12lives

    12lives If it runs, it's done!

    Last edited: Mar 10, 2021
  9. sean Buick 76

    sean Buick 76 Buick Nut

    Tom miller did a 11:1 engine with a TA 212 cam and stock manifolds for a FAST setup and it worked really well. I can’t remember the 1/4 times but it was very good.

    yes Ta has the headers flanges but mine are $40
    Last edited: Mar 9, 2021
    12lives likes this.
  10. sean Buick 76

    sean Buick 76 Buick Nut

  11. Dano

    Dano Platinum Level Contributor

    That's the real question here - Would be shorty headers provide any increase in performance & if so how much. We might need to find out.

    Thanks - I was aware of that. I have two (2) 350 GS's & was thinking of maybe making one stock appearing.
    IIRC @Tom Miller ran high 12's with a 4.?? (.56 or .88 I think) rear & said the car wasn't really streetable - Maybe he'll chime in here with some details of what it ran & what he did to get it to that level.

    I should probably get a pair of your flanges. I have a set of TA headers and planning on dialing in a couple of m/l stock (#'s matching) engines for the the GS's in a Skylark test mule (have 2 other engines to subsequently build for the cars) and could maybe experiment between std. iron, ported iron, shorty, and long tube headers. Maybe it won't make much difference on a stock engine. Idk.
    Last edited: Mar 11, 2021
  12. Jim Blackwood

    Jim Blackwood Well-Known Member

    The reason long tube headers have a tube length of around 32" is because that's what it takes to have suction at the port the next time the valve opens. So you should see a significant boost over shorties. It also makes a difference if they are equal length tubes. Many production headers can have deviations of up to +_ 2" in tube length. Since shorties cannot generate port suction they are only a little better than cast manifolds, based completely on flow smoothing.

    sean Buick 76 and Dano like this.
  13. Keith Harman

    Keith Harman New Member

    Hi. Does anyone know if 350 skylark manifolds are the same for a 350 GS ? Thanks Keith
  14. Dano

    Dano Platinum Level Contributor

  15. Mark Demko

    Mark Demko Well-Known Member

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