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School me on intake manifolds and headers

Discussion in 'Engine & Performance' started by bigcountry78, Aug 19, 2019.

  1. Frankenchevy

    Frankenchevy . Supporting Member

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    Also consider the vehicle when reading anecdotal evidence pertaining to open air element filters on forums.

    A Corvette or Camaro doing in town driving will have much higher under hood temps than a 4x4 pickup with a large grill and no inner fender skirts circulating air around an engine bay that could fit 3 small blocks on a 55mph commute with 2 stop signs.

    There are many variables to each combo. I am looking around for a cold air intake, but I’ve read about certain downsides on that side, too. I may get a oem type dual snorkel here, but I’m not expecting miracles.
     
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  2. bucket

    bucket Super Moderator Staff Member

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    It depends on the power needs. A higher HP engine will do much better with plenty of hot air rather than a limited supply of slightly cooler air.

    As was pointed out, an old truck is going to have relatively low under hood temps. And if it does get cooking hot, it's because is very hot outside the truck too, so an intake tube wouldn't be pulling in very cool air anyway.
     
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  3. bigcountry78

    bigcountry78 Full Access Member

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    These are the headers. I have no idea what brand, but they seem well made.

    42B931D5-FDE2-43B0-BE63-0A7080EB7006.jpeg
     
  4. legopnuematic

    legopnuematic Supporting Member Supporting Member

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  5. Dooley

    Dooley Full Access Member

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    Spend a little time and you might locate a cast iron high rise version of Chevrolet's aluminum high rise that was in the original Z28.
    It's heavier but, also is flanged for both carbs, Rochester and Holley. GM # 14096011
    If you are wanting an aluminum intake and not a high rise intake the one from an L82 engine has everything you would need for moderate street performance.
    GM #14004377 or a GM3458520.
    View attachment 124705

    IMG_2578a.JPG

    oe%20highrise%203.jpg
     
    Last edited: Aug 22, 2019
  6. bigcountry78

    bigcountry78 Full Access Member

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    I’ll keep that one in mind.
     
  7. bigcountry78

    bigcountry78 Full Access Member

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    I really don’t think I’d lose anything by going to an open element air filter.

    83F6396F-AC50-4637-8118-C3BC1060C470.jpeg
     
  8. trukman1

    trukman1 Full Access Member

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    Easy way to find out is to turn the air cleaner lid upside down. That will give you enough additional air to see if you can tell the difference. If so, you may want to go open element. If not, no reason to waste the money, IMO.
     
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  9. MikeB

    MikeB Full Access Member

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    Don't forget to check the ignition advance curve. Not sure about your 78, but in order to keep emissions in check, many engines back then had little to zero advance at idle, and vacuum advance didn't kick in until part throttle. It might be necessary to mess with springs, weights, and even vacuum canister. I suggest Googling "high performance ignition advance" to learn about optimal timing. You'll be surprised at what some minor mods can do for performance and fuel mileage.
     
  10. ali_c20

    ali_c20 Full Access Member

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    This video contains some good information... the difference in hp and torque is not that big and they have 450+ hp engine.
     
  11. bucket

    bucket Super Moderator Staff Member

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    But in that test, they used a pretty decent set of manifolds. The average 70's and 80's manifolds were the log type.
     
  12. ali_c20

    ali_c20 Full Access Member

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    That's true, The truck logs are surely worse than the hooker logs. Here is an article from hotrod magazin with a stock log type manifold ( which appears to be better than the 70 truck ones too.). https://www.hotrod.com/articles/hppp-0312-headers-vs-manifolds/ If you really want to know what is the best for your application you would have to mount and dyno the parts you want to use.
    Tests like this just give you a rough idea of the difference the parts make.
     
  13. Backfoot100

    Backfoot100 Full Access Member

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    I wouldn't say the results are that close.

    The difference between the manifolds and long tube headers was something like 15HP!!! On a 400+ HP engine that's still pretty significant.
    Figure that a set of cheap headers runs $200 on the high side for a 15HP increase. I'll take those numbers all day long. You have to consider the HP/dollar ROI. By far the cheapest HP increase you ever spend money on.

    As stated, the manifold for this engine is almost a shorty header already. Even the guy pulling the dyno stated that 20 years ago the long tubes would be the way to go, hands down. No questions asked.

    Its been proven for decades that the easiest and cheapest upgrade to increase HP on a factory engine is with a set of long tube headers. This test still proves that. The advanced design of the manifolds in this particular case just makes that increase less than what is normally anticipated.
     
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  14. KS2506

    KS2506 Junior Member

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    I had a '73 3/4 ton 4WD, 410 gears, limited slip rear, 12:50/ 16.5's, mud and snow tires, Hedman headers, Corvette fuel injection cam, Offy manifold, Holley 650 cfm carb. Best truck I ever had. Real mud and snow goer, Lots of pulling power. Get rid of the Quadra Jet and get a Holley spread bore, much better and easier to tune. Good Luck with your project.
     

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