Has anyone ever tried something like this with the stock log exhaust manifolds?

Engine, Transmission & Driveline

  1. WissaMan

    WissaMan Member

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    This was just a quick mock-up of an idea I had of taking two sets of manifolds, cutting them and welding them into a dual-outlet setup. Why? Better flow than stock w/o the headaches and noise of headers...maybe. And to be unique and different :) Would require some custom piping of course. Could neck them down to one pipe right off the manifold, run them back to a y-pipe to combine them or run two 2" pipes per side all the way back. I have to wonder what that would even sound like, might be interesting!

    I realize because of the firing order the flow out each of the 4 outlets wouldn't be perfectly balanced. I also wonder what the pros/cons are of leaving the passage between the pairs open vs. welding it shut.

    Just another one of hair-brained ideas that popped into my head...


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  2. WissaMan

    WissaMan Member

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    sorry for the 3 duplicate images. I tried to edit and delete two of them but could not for some reason...
     
  3. Davea Lux

    Davea Lux Senior Member FCBO Gold Member

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    It will be really tricky to get the forward dump on the driver's side to clear the steering gear. We used to do a dual dump like this on 235 cid Chevy six cylinders to convert them to dual exhaust and they actually sounded pretty mellow with cherry bomb glass packs. (Blocked of the original center line port) A constant problem with welding cast iron is getting a good weld without any cracks. Really should be forge welded. Log manifolds were not noted for their high flow characteristics because the exhaust comes hot out of the port and pushes straight out into the side of the manifold causing back pressure. This will still be an issue with a dual dump but I suspect the a considerable flow gain might be possible. If you have the requisite equipment and welding skills, it would be fun to experiment with it. You will probably go thru a bunch of log manifolds before you get it right. Good luck.

    Dave
     
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  4. The Goose

    The Goose Senior Member

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    Even more exhaust pipes to burn myself on LoL!!!

    Diabolically sacrilicious...
     
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  5. The Goose

    The Goose Senior Member

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    Yah maybe join em w pipe inside. We used to go thru head pipes and thermal reactors on our 76 Rotary pickup. They just were impossible to weld after they cracked in half.
     
  6. cbarge

    cbarge Senior Member FCBO Gold Member

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    HP logs or headers..
    The logs were designed by Chrysler engineers whom were the best among the industry at that time.
    Good idea but as mentioned difficult to execute.
     
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  7. stubs300

    stubs300 Senior Member

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    If it ain't broke, why fix it?
     
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  8. 70bigblockdodge

    70bigblockdodge Old Man with a Hat FCBO Gold Member

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    They will only help marginally. The trick is to get the ports to dump at the same place and in the same direction. As the pulse from any given cylinder enters the collection point (usually a larger diameter section than individual cylinder ports/tubes) it flows into a larger volume (as we know from our physics lessons) as volume increases the pressure and temperature go down causing a scavenging effect on the other ports/tubes. This why headers work even the shorty ones, HP exhaust manifold are not much better than the logs because they don't collect in the same area although they do point the flow in the right direction it still crosses other ports on its way to the outlet/exhaust flange.
     
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  9. CBODY67

    CBODY67 Senior Member

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    The idea of having ore exit port area is valid. But the pressure pulses in the manifold might get "confused" and result in more internal turbulence in the manifold itself. Just my theory.

    Perhaps taking one of the '74-era normal exhaust manifolds and extrude honing it would be a better alternative? Should be a bit more flow without all of the fitment/clearance/piping issues?

    I remember the "split manifold" kits for the inline Chevy 6 cyls of the 1950s. Our high school band director had a '53 Chevy coupe with that set-up on it. Sounded different. A bit out of character for the man, though. I thought, at the time, "Why bother with a 6 cyl Chevy?" At the time, I was driving out '51 GMC 1/2 228 4-speed pickup to school. It ran better than the Chevy 6s did, from what I could tell.

    "Hair-brained ideas" CAN lead to real innovations!
    CBODY67
     
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  10. WissaMan

    WissaMan Member

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    Yeah, I'm sure it wouldn't be optimal in terms of turbulence, scavenging, etc. as compared to headers. It'd be more of a thing to try "just because" and to be unique. I did read that welding cast iron takes some extra care to prevent cracking. Mainly that you have to preheat the piece to operating temperature, weld, then very slowly cool it. I would be curious to hear the sound of a 440 through a 4 pipe exhaust too. Might sound like crap. Might be cool.

    It's interesting you mentioned the term "split manifold". I remember when I was in elementary school, our bus had dual tailpipes while every other bus just had the 1 big tailpipe. It sounded pretty cool too and especially when the driver would shift there'd be some crackle and popping. I remember I was told it had a split manifold. I had no idea what that meant at the time but it was told to me in such a way that I knew it must be something cool. Unless maybe that was just one of those stories kids tell other kids. But it did have dual exhaust, that much was obvious, and it was the only bus in the district with duals. Made me feel kind of special riding on it :)
     
  11. Mr onetwo

    Mr onetwo Active Member

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    Instead of trying this in cast iron(iffy at best) why not fabricate it out of steel tubing and sheet.

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