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Gill exhaust hp
I have gill exhaust with 4" od dry pipes and looking to upgrade my motors to 650 hp will they handle it or is it time for headers?
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Staying NA your power will be better with a sweeper style header or the thunder and lightning manifolds. The longer equal length runner helps for NA |
I posted this same question in a slightly different way earlier in the week on my build thread. I too am curious to know at what point a NA build is limited by manifold style exhaust.
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It has a lot to do with rpm. If you’re gonna turn 4500 rpm you’d be fine. If you’re gonna turn 550+ you will be limited. Even the 525 uses a sweeper style header and it’s a 5200 rpm motor |
Mark rinda did a dyno test on a mild 509. Going from open manifold to thunder n lightning which is a full length runner manifold and the power was around 35+ with the full runners |
So let's look at a 500 efi with an E-top style header. Works well with a header that is only a slight improvement over a good manifold. I would say it would be safe to say that a NA 500" with cam similar to 500efi wouldn't give up much power utilizing a good manifold and riser. Then you look at a 525 with full length sweeper headers. Can it be determined that somewhere between a 500EFI and 525EFI is where we draw the line for making good power with a good flowing manifold? To the OP I believe for you it is time for headers of some sort whether that be thunder and lightnings or cmi whatever something full length divided runner. Stainless marine has some options as well that support big power.
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Vortec 8100 / 8.1L / 496MAG Mercury Marine Performance Parts Upgrade - Raylar Big Power
One of the best non bias tests out there. Later on bobl tested a set of 496 CMI sport tubes on the same dyno and they picked up a few hp over the dana's. The stock 496 manifolds are a individual runner Gill design and dump into a riser. The Dana setup is a much longer internal runner design that carries into the riser. As power levels rise, the difference between the two types of exhaust will only grow. Your current setup will work fine. Are you leaving power on the table vs a long runner header? Absolutely! Hard to beat the price vs performance of these.... https://cimg6.ibsrv.net/gimg/www.off...624e3ebbc5.jpg |
The gils work fine in his app but he will need to make more power to reach his goal. 650 with a gil would be closer to 700 with a true header. Now if it’s all about making 650 on a dyno with no accessories and dyno headers than that’s a different ballgame. When I think power numbers I think fully dressed in marine trim. |
[QUOTE=Crude Intentions;4641019]
The gils work fine in his app but he will need to make more power to reach his goal. 650 with a gil would be closer to 700 with a true header. Now if it’s all about making 650 on a dyno with no accessories and dyno headers than that’s a different ballgame. When I think power numbers I think fully dressed in marine trim. TE]yes dyno rating undressed. |
Oh well it won’t be close to that in the boat so use whatever you want. Lol. 650 undressed through dyno headers is loellyncloser to 570 in the boat anyhow. |
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