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Headers vs. stock manifolds

Discussion in 'The Garage' started by Ressurection, Feb 7, 2007.

  1. Ressurection

    Ressurection 1/2 ton status

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    Got a very negative opinion of headers from an exhaust shop recently. His issues are the finish (unless you spend a boatload of $), and cracking at the collector, etc.

    He also said the performance gains are nominal.

    What are your thoughts?
     
  2. RootBreaker

    RootBreaker 3/4 ton status Premium Member

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    i am running autozone cheapos.... $75 and yeah they are rusted bigtime already.... but they dont leak... my next ones will be shorties....

    cant tell you the differece between my truck without them and with them as my truck went major surgery when it went on the road... when that happened.... well it got tons of stuff... motor, exhaust parts... lift to lower the truck... new tires... rims... d60... gears... detroits.... cross over steer.... and tons of others....


    I do notice that on all the trucks, xtreme 4x4, powerblock tv.. when they put headers on they gain... but gotta remember.... the more air you allow in the more that has to exit... so maybe on a stock motor there may not be much of a difference....

    also I remember someone saying... 2 /14" exhaust will give you better torque over headers and full 3" exhaust.... so not too sure... sorry not much informative but hopefully it helps a bit....:crazy:
     
  3. 1977k5

    1977k5 3/4 ton status Vendor

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    I made this post in another thread, but I will continue to throw this kind of stuff up until people stop with the misconception that smaller exhaust makes better low end torque. Here it is:


    Headers that all have the same length primaries actually scavenge the exhaust from the pipes. As the engine runs, it makes pulses through each primary. If all of the primaries are the same length, they move through the collector one after the other. This creates an effect (I believe called the venturi effect) that actually creates negative pressure behind the pulse. This "sucks" exhaust out of the other 3 primaries and hence makes more power.

    This only happens if the primaries are all the same size. Practically no one with our trucks runs them because they are expensive and can be difficult to fit with front driveshafts etc. If you have these headers, then it is important to fit the primary/collector/exhaust pipe size to the size of the motor and the intended RPM.

    If you are not running headers that have equal length primaries, the bigger exhaust the better. Period. Less backpressure means less work to push the exhaust out, less exhaust left in the combustion chamber and hence more air/fuel that gets drawn back in.
     
  4. Ressurection

    Ressurection 1/2 ton status

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    so far so good....keep up the input! While you're at it, how bout thoughts on stainless steel?
     
  5. 1977k5

    1977k5 3/4 ton status Vendor

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    On topic, I run flowtech (the cheapest, ~$70 I think) headers. I had one primary break all the way around such that that cylinder was basically running open exhaust shortly after the head. They have a lifetime warranty and the company I bought them from replaced both headers without a hassle, I had them about 4 years before it cracked.

    I have pretty much always had at least a small exhaust leak with these. That is because they have cheap (thin) flanges. I'm still glad I have them rather than my stock manifolds, but maybe I am willing to put up with the quirks more than most :wink1:
     
  6. 76zimmer

    76zimmer Flyin Rat Premium Member GMOTM Winner

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    I have run the ceramic coated Dynomax headers, and they were rusting with 3 years, and not driven in the salt. I definitely agree that the performance is there if you tune for it.
     
  7. cybrfire

    cybrfire 1 ton status Vendor GMOTM Winner

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    As far as finish is concerned, I've never seen a exhaust manifold that wasn't rusty.

    They do improve performance. Most times just bolt them on and there is a difference. Noticeable difference, probably not. You do need to tune for them in my opinion. I'm no engine guru, I leave that stuff to superwrench!

    I've never had one crack either. Luck maybe??

    I also never use the 3 bolt collector flange. Cut that lip off and slide a reducer over the header and weld it on. From there use the standard exhaust clamps. Much simpler!
     
  8. pauly383

    pauly383 Daddy383 Staff Member Moderator

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    All I can say is spend the money on a good set , spend some more on good gaskets , and spend even more on good locking fasteners .

    If you do have cheapies , take the time to get the exhaust pipes situated , and then tack weld them , pull them off and fully weld that 3 bolt flange all the way around , on both collector and pipes .

    Hooker , Percy's , and Stage 8 are going on my Chevelle .
     
  9. SlicksInRain

    SlicksInRain 1/2 ton status

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    I currently have Hooker Headers and their great. I had Dynamax for about 2 years and one cracked. When I bolted them onto my then stock engine I noticed a little difference off the line and a cool roar.
     
  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Basically....you'll only really feel a set of long tubes if you add them to a built motor making some power that had manifolds before. Also, you have to have the rest of the exhaust free flowing to match.

    I wouldn't bother with a stock engine and/or exhaust. You likely won't feel anything due to a stocker not flowing a lot of air like a built up engine.

    I felt some power gain when I put Hooker long tubes on my 406, but it was the perfect conditions for a gain to be seen. 325HP motor, big cubes for a small block, and stock manifolds on before.

    I wouldn't of done it to an old 350.

    Spend some money on a set of headers and more importantly buy good aluminum gaskets.
     
  11. blazin_blazer

    blazin_blazer 1/2 ton status

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    i like to run factory exhaust manifolds...i'm lucky enuff to have a company locally that does extrude honeing and i've had a couple sets smoothed and bored out....

    the cast manifold is designed to keep the exhaust gases hot because the hotter the gases the faster it is moving...i had a set extruded and then smoothed them and had them chromed(chrome is supposed to retain heat , so it looks good pluss it helps hold in the heat also)...that and it won't fade your hood near as bad.

    i pick up everyset that i find that has the cast bar across the top of the outlets. i've had them spring on me and the bolts not line back up, so i look for the manifolds that have that heavy bar cast across the top of them. any1 have those?
     
  12. TheAustrian

    TheAustrian 1/2 ton status

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    I run Flowtech headers. I got a set of high quality gaskets since I was told to better spend more money on them. I also added a 500 Edelbrock carb, Edelbrock air intake manifold and a Edelbrock performer camshaft and after the header a true 2 1/4" dual exhaust system. The headers and dual exhaust system came later then the other modifications. I could feel two times an increase of power. First the performer package was installed (no headers and no dual exhaust), very noticeable increase. And when I installed the headers with the dual exhaust system, again much more power recognizeable. So it is true that headers, in connection with bigger exhaust gains a lot of power. And the more you change on the motor, the more they bring benefit.

    I also red an article in an older 4-wheel or 4x4 magazine. They took a standard 350 gm sb motor, added headers (Flowtech I think) and some flowmaster mufflers. The test run showed a gain of about 20hp and more than 16lbs torque. Just by adding headers and mufflers with lower backpressure. So, I believe it is worth to add headers and a bigger dual exhaust system and also improving something on the motor side.
     
  13. Ressurection

    Ressurection 1/2 ton status

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    Thanks for the input, I'm keeping the engine mostly stock (may do a mild cam...again thoughts?), but am planning on dual exhaust. W/ dual, what do you guys think about a crossover?
     
  14. mogulmasher

    mogulmasher Registered Member

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    I have a set of those manifolds. Found them thrown out on the side of a trail years ago! I've only seen one other set at a swap meet and they wanted big money for them! Any idea what gm vehicles these came from the factory on?
     
  15. scooter122983

    scooter122983 1/2 ton status

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    Crossover? Like a H pipe or X pipe? In one of our trucks i believe it would be a pain to do a X pipe but a universal H pipe would be the easiest.
     
  16. TheAustrian

    TheAustrian 1/2 ton status

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    what for is a X or H pipe?
     
  17. gmc4cw

    gmc4cw 1/2 ton status GMOTM Winner

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    :doah: why didn't I think to do this. every set of headers I have owned had the collector flange hit the shackle bolt. you are one smart fellow.

    if you just put headers on a stock motor you probably will not notice much if anything. When I had my motor built the guy who built it told me that I needed to run headers to get everything out of it.
     
  18. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Well how about shorties? I plan on buying the Edelbroc ones that are a direct bolt on installation. They come in either the Ti-tec coating or stainless steel, which is better as far as rust prevention?
     
  19. bajaviking

    bajaviking 1/2 ton status

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    As far as I have been told shorties does not improve torque so why even bother.
     
  20. twodollars

    twodollars Registered Member

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    The shorties would be better than a small outlet, restrictive factory manifold, but I wouldn't bother unless the engine was pretty well warmed over - and if anything I would use long tubes. Another good exhaust manifold choice would be the later (relatively) L98 cast manifolds from the camaro / firebirds. They had 2 1/4 outlets, and were not too bad of a design. The cast manifolds are usually much more durable and leak free. Don't get me wrong, if you had a cam and carb on a stock engine, perhaps you could get a few horsepower out of the headers - but I doubt you could feel even 15 hp - especially in a 6000lb truck. A good set of dual pipes on manifolds provides a good balance of cost and performance, in my humble opinion. Of course, headers are just cool to have. Who doesn't like that?
     

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