Anyone ported 440 hp exhaust manifolds for racing class requirements and your findings!
Porting hp 440 manifolds
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Challenger340
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This will be interesting.
There was much hype round "extrude honing" Exh Manifolds years back.... but I dunno if anyone ever documented testing therein ?
There was much hype round "extrude honing" Exh Manifolds years back.... but I dunno if anyone ever documented testing therein ?
The builder on my wedge suggested I get my MW ex manifolds extrude honed. I just couldn't justify the extra $$ for the gain in power. We were already at 600+ for HP & Trq, and it's not a race motor...
steve340
Well-Known Member
I have hand ported a few sets years ago but have no dyno results. I saw a magazine article on extrude honing a number of years ago and I am sure it would help but it was fairly expensive then. Are they still in business?
There is a fellow named Bresinsky (spelling??) who does a lot of porting of Chevy stock intake manifolds and exhaust manifolds. He is very clever and goes to great lengths but I am certain it is not cheap to do what he does. Have a look for him he does videos on You Tube.
I am guessing but the exhaust manifold porting might be worth 3 to maybe 10 HP.
More likely the lower end of my guess. The gain won't be huge unless the manifold is way off.
The torque gain could be more than that if you are lucky. This increase is really what you need. Focus on more torque production not horsepower for stock class drag racing.
The correct cam timing numbers will be critical for what you are planning.
There is a fellow named Bresinsky (spelling??) who does a lot of porting of Chevy stock intake manifolds and exhaust manifolds. He is very clever and goes to great lengths but I am certain it is not cheap to do what he does. Have a look for him he does videos on You Tube.
I am guessing but the exhaust manifold porting might be worth 3 to maybe 10 HP.
More likely the lower end of my guess. The gain won't be huge unless the manifold is way off.
The torque gain could be more than that if you are lucky. This increase is really what you need. Focus on more torque production not horsepower for stock class drag racing.
The correct cam timing numbers will be critical for what you are planning.
66Satellite47
Well-Known Member
As I recall the stocker guys did get something out of it. Seems like a lot of time & effort for not much. But that's the NHRA stocker world.
Raymond Murray
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Randy Brzezinski
66Satellite47
Well-Known Member
I must be livin' in the past. LOL
69SportSatellite
Well-Known Member
Regarding the results of extrude honing on a near stock build, as part of the well known "440 Resto to Rad" article, they had their HP manifolds extrude honed. This is from the article:
"The HP exhaust manifolds on the test 440 were a respectable design. As an upgrade, they were swapped for a set that had been Extrude Honed. For those unfamiliar with the process, the Extrude Hone system forces a thick slurry of abrasive paste through a passage under high pressure, which removes material, enlarging the passage and laving a smooth surface.
With the Extrude-Honed manifolds in place, the 440 made 367.1 hp @ 5,100 rpm and 481.7 lb-ft, a gain of 0.9 hp and 7 ft-lb. Interestingly, the biggest gains were in torque at lower rpm and predominately below with less power added by peak horsepower and beyond."
"The HP exhaust manifolds on the test 440 were a respectable design. As an upgrade, they were swapped for a set that had been Extrude Honed. For those unfamiliar with the process, the Extrude Hone system forces a thick slurry of abrasive paste through a passage under high pressure, which removes material, enlarging the passage and laving a smooth surface.
With the Extrude-Honed manifolds in place, the 440 made 367.1 hp @ 5,100 rpm and 481.7 lb-ft, a gain of 0.9 hp and 7 ft-lb. Interestingly, the biggest gains were in torque at lower rpm and predominately below with less power added by peak horsepower and beyond."
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In the far, far reaches of my memory, I recall someone in our car "circle" getting their modified engine exhaust manifolds extrude honed. Dyno'd hp increase was only in single digits, don't recall any clearer.
Yes , I’m familiar with the extude honing , expensive and nothing more than cleaning rough edges ! Ok thanks guys for the comments! Just curious! Thanks
steve340
Well-Known Member
I have no idea about your budget.
Good cylinder head work and a custom ground camshaft is likely to bring the most gain and not be super pricey.
You can hog a fair bit out of a stock intake manifold as well.
You may have already done this I suppose.
Good cylinder head work and a custom ground camshaft is likely to bring the most gain and not be super pricey.
You can hog a fair bit out of a stock intake manifold as well.
You may have already done this I suppose.
Ask on the F A S T Facebook page. These guys run manifolds.
https://www.facebook.com/fast.races.7
Doug
https://www.facebook.com/fast.races.7
Doug
Runcharger
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B manifolds are fairly thin and are known to crack. I wouldn't do it for 1HP.
PRHeads
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I know someone who did the test on a chassis dyno....... back to back.
It was basically zero gain.
It was basically zero gain.
Yes , ok thanks
steve340
Well-Known Member
I agree there is not much to be gained but it is not going to hurt to give them a little buzz to get rid of any obvious lumps and to make sure they do not block off any of the exhaust port.
Every little bit of power/torque is going to help.
Every little bit of power/torque is going to help.
Agreed
Can you use any cast exhaust manifold? If yes, and you have the wallet, then the Max Wedge manifolds flow almost as good as headers. Look up Nick's Garage on youtube he has done a comparison between HP manifolds, Max Wedge manifolds and 1 7/8 headers on his dyno.
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