HO manifolds vs Shorty Headers
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Car: 89 Firebird
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HO manifolds vs Shorty Headers
So..I have a set of the better TPI manifolds and a set of 2460 Hooker headers. Would be going with a Magnaflow Y-pipe or Doug's D901 for the hookers. Car already has 3in exhaust system cat-delete that will butt up to which ever one I choose. So how much power would i lose staying with the manifolds vs the headers? Pretty much stock L98 350 running TBI. If it's not a lot of difference id like to stay with manifolds for obvious reasons. What do you guys think or what are your experiences. In the past I've always went with headers but I'm not racing this one.
Last edited by dmccain; 07-21-2019 at 01:58 AM.
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Car: '90 Trans Am-12.45@110.71
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Re: HO manifolds vs Shorty Headers
Regardless of the outlet, the inside of the manifold is still less than 2" for all 4 cylinders.
#4
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Re: HO manifolds vs Shorty Headers
Not to hi-jack your thread Dustin but can some one elaborate on the tpi manifolds? There are different options? The reason I ask is I have a spare 88 parts car with a complete tpi. Other than my 87 not having the same emissions crap the 88 has I didn't know there was a better set of manifolds, of course I was just assuming.
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Car: '83 Firebird (T/A Clone)
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Re: HO manifolds vs Shorty Headers
Headers will always out-flow exhaust manifolds. You'd probably gain around 15 horsepower with headers.
Of course there are drawbacks as well. Headers dissapate a lot more heat into the engine compartment, are notorious for leaking, and don't tend to last as long as exhaust manifolds. I have the '84 HO exhaust manifolds, but I'm not going drag racing with this car...
Of course there are drawbacks as well. Headers dissapate a lot more heat into the engine compartment, are notorious for leaking, and don't tend to last as long as exhaust manifolds. I have the '84 HO exhaust manifolds, but I'm not going drag racing with this car...
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Car: 1989 Firebird GTA
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Re: HO manifolds vs Shorty Headers
Nothing wrong with manifolds on a street car, especially if you want stock stealth. With the right kind of work, they will support a surprising amount of power, especially on "torque" engines like "stock" 350's. I ran a race car with manifolds, and - trust me - they flowed. Now, you may not want to do a lot of work to them, I had to, but it is possible. If you are not racing, and don't want to mess with header bolts, gasket leaks...… just wanna drive, stick with them. Header power is most noticeable at higher rpm, and a shorty header has a relatively small range of power advantage....
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T.L. (07-22-2019)
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Car: 1986 trans am
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Re: HO manifolds vs Shorty Headers
there are two styles ,one is about 1 and 7/8 to 2" (usually on lb9 automatic cars) and the ones on the hotter LB9 5 speed and L98 cars are closer to 2 1/4" ,
there are exceptions and specifics on years applicable,search deeper for the exact definitive answers,many on here know the exact information you need.
there are exceptions and specifics on years applicable,search deeper for the exact definitive answers,many on here know the exact information you need.
Last edited by 1986BANDIT; 08-17-2019 at 04:46 PM.
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Re: HO manifolds vs Shorty Headers
Nothing wrong with manifolds on a street car, especially if you want stock stealth. With the right kind of work, they will support a surprising amount of power, especially on "torque" engines like "stock" 350's. I ran a race car with manifolds, and - trust me - they flowed. Now, you may not want to do a lot of work to them, I had to, but it is possible. If you are not racing, and don't want to mess with header bolts, gasket leaks...… just wanna drive, stick with them. Header power is most noticeable at higher rpm, and a shorty header has a relatively small range of power advantage....
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1986BANDIT (09-14-2019)
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Car: 1989 Firebird GTA
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Re: HO manifolds vs Shorty Headers
There are models that are prone to poor performance and breakage due to the design needed to make them fit, but the 3rd gen f body manifolds are not known for such problems....
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Car: 1991 Z28
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Re: HO manifolds vs Shorty Headers
Nothing wrong with manifolds on a street car, especially if you want stock stealth. With the right kind of work, they will support a surprising amount of power, especially on "torque" engines like "stock" 350's. I ran a race car with manifolds, and - trust me - they flowed. Now, you may not want to do a lot of work to them, I had to, but it is possible. If you are not racing, and don't want to mess with header bolts, gasket leaks...… just wanna drive, stick with them. Header power is most noticeable at higher rpm, and a shorty header has a relatively small range of power advantage....
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T.L. (09-14-2019)
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Re: HO manifolds vs Shorty Headers
if anyone can find a good place that does the extrude honing process,some very serious flow gains could be had and be virtually undetectable from the outside.
the same benefit applies to tpi runners,tpi base etc.the extrude honing pumps an abrasive slurry through the ports and removes material evenly and smoothly.
the same benefit applies to tpi runners,tpi base etc.the extrude honing pumps an abrasive slurry through the ports and removes material evenly and smoothly.
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Re: HO manifolds vs Shorty Headers
Bonehead performance quoted me $910 to extrude hone my 3 piece mpfi intake manifold plus shipping. just to get an idea of the cost. I decided I could do enough with my Dremel.
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Re: HO manifolds vs Shorty Headers
The Elcamino was a LG4 and had the same manifolds as a mid 80s F-car. I replaced them with F-car shorty headers in that car. Plug access was 10x better and it had a definate power increase. Worked really well when the Q-jet/Performer intake swapped 85 LB9 long block went into it too.
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Re: HO manifolds vs Shorty Headers
Given the option headers over manifolds any day. The last car I helped setup for a friend has shorties. Just swapping the shorties even made the car sound better.
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