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Thread: 3400 vs 3500 exhaust manifolds

  1. #1

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    Question 3400 vs 3500 exhaust manifolds

    I am going to be running a 3500 in my currently 3400 swapped Fiero and I need clarification regarding the exhuast manifolds.

    The 3500 is out of a g6 and I am not planning on using the dual manifolds that came with it, I simply do not want to redesign my exhaust (or is this worthwhile?

    Anyway, I have been looking at using manifold with a crossover like the 3500 equipped vans came with. I looked some up on car-part and 3400 manifolds keep on popping up, are they exactly the same or will I have to do some porting to match them up to the heads? Do they flow the same as the simial (or is it same?) 3500 manifold?

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  3. #2
    Been there, Built that. Superdave's Avatar
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    Quote Originally Posted by FieroLuke View Post
    I am going to be running a 3500 in my currently 3400 swapped Fiero and I need clarification regarding the exhuast manifolds.

    The 3500 is out of a g6 and I am not planning on using the dual manifolds that came with it, I simply do not want to redesign my exhaust (or is this worthwhile?

    Anyway, I have been looking at using manifold with a crossover like the 3500 equipped vans came with. I looked some up on car-part and 3400 manifolds keep on popping up, are they exactly the same or will I have to do some porting to match them up to the heads? Do they flow the same as the simial (or is it same?) 3500 manifold?
    the 3400 manifolds will fit and work fine altho they do not flow as much as the 3500 ones.

    here is a 3400 gasket on a stock 3500 head...

    http://www.3500z.com/3500/Copy%20of%...3500%20027.jpg

    you can kinda see how big the 3500 ones are VS the gen2 aluminium head ones here...

    http://www.3500z.com/3500/mini-3500%20019.jpg

  4. #3

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    The crappy part is that this is all due to budgeting, if I had the 3500 to begin with it would have actually been easier to build an exhaust using the g6 manifolds (barring the huge downpipe flange that is on one of them getting in the way)

    Now the question that remains for me is do the 3500 Van manifolds w/ the crossover differ any from the 3400 manifolds I have?

    "Ponders redoing exhaust anyway"

    PS. off topic, are those dyno'd numbers off your car? If so, wow, impressive.
    Last edited by FieroLuke; 03-29-2007 at 12:18 PM. Reason: added some thoughts

  5. #4
    Been there, Built that. Superdave's Avatar
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    no real numbers yet, they'll be coming in the next few months...

    that's just an estimate from a sym program.

    I didn't think the 3500 LX9 made it into any vans..

  6. #5
    Mr. Orange. IsaacHayes's Avatar
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    I would say it's worth using the dual 3500 manifolds. Why not do it right than re-do it again down the road? Or do custom
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  7. #6

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    Yup we had a bunch of '05-'06 chevy uplanders and pontiac montanas with the 3500, up in Canada anyway, the new 07's though have the 3900 in them.

    I'll probably just do the 3400 manifolds for now to save money, having just bought a house I dont know if I will drive the fiero this year, only one toy allowed and the v8 volvo wagon is a lot more practical for my wife and two dogs to come along in.

    The 3500 manifolds will be stashed away though because they look to have a nice flow and the only money loss of doing 3400's for now is the gaskets, I already have the exhuast setup in the car to run 3400 manifolds.
    Last edited by FieroLuke; 03-30-2007 at 01:18 PM. Reason: wanted email notification of posts

  8. #7
    The Pink Car 3400-95-Modified's Avatar
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    I'm using 05 3400 Impala exhaust manifolds.

    The are larger than 01 3400 ones... I'm not sure when they started making these but they may be the 04-05 3500 crossover style that they just slapped on a 3400.

    Pics to show what I took off of the 3400 Impala.

    Well guess what, A 05 Impala 3400 comes with cross over style exhaust manifolds with the 3500 sized ports... It also had the 3500 manifold gaskets on it.

    This is a big find for anyone who needs this style manifold and is using a 3500 top end.

    I found this out when I took apart my 05 3400.







    Against the dinky 3400 port on the head.




    Comparison to a 01 3400 manifold gasket I had lying around


    I guess I know what manifolds I'll be using when I do my swap.

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  9. #8

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    Wow that is a pretty big difference in port size, definately have to keep my eye out for a set of those. I still dont know why car-part would list them as the same thing, just because it bolts on doesnt mean it interchanges *grumble*

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