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ProStock Jackstand Winner
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Discussion Starter #1
I assume you want a different duration split on a nitrous stick versus an automatic, question is would you want more duration split or less split?
 

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Gigity
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3,140 Posts
I think engine combo will dictate what it wants, and a cam guru will take your gear ratios and whatnot into consideration when deciding on the valve events for your setup.
That said I was in dis belief when I got the cam specs for my LS for my setup - 26* of split. But I beleive this was mainly because of the cylinder heads details more than anything.
Barrett
 

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ProStock Jackstand Winner
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Discussion Starter #3
I have cam here with 16 degrees of duration split and was told i need 14:1+ and/or hit it with at least 450 to really make use of it
 

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Gigity
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3,140 Posts
mine made 648hp @ 7500 N/A at 364CI( 6.0L).
Some will say a big split is to crutch a poor exhaust, but it really comes down to pressure differentials, you need to blow the exhaust out completely to breath the fresh stuff in. A really wicked intake port with an average exhaust port will need a big split to carry power high into the rpm range, at high rpm - thats what i am dealing with running a carb on LS3 heads on a 6.0
What is your engine combo Damon?
 

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ProStock Jackstand Winner
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Discussion Starter #5 (Edited)
358" 23* sbc. 13:1 compression. ported 225cc heads, Brodix Sp1 intake, hp950 carb. 3.500stroke, 4.030 bore. 300hp plate.

the old combo was same shortblock with unported 200cc heads and a holley strip dominator.hp750 carb, 300hp plate. cam was 246/254 @.050, .562/.580 lift with 1.52's 110lobe
 

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Gigity
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3,140 Posts
I have cam here with 16 degrees of duration split and was told i need 14:1+ and/or hit it with at least 450 to really make use of it
well , I'm not a cam guru, but from a purely theoretical standpoint I would think a LOWER compression engine would benefit more than a highCR engine, from greater exhaust duration created by more "split", as it would have a lower expansion ratio on the power stroke, and therfor have more residual pressure in the cylinder.
regarding the nitrous, I can see greater volume of spray needing more exhaust duration as well, simply because there is more exhaust to get out.
The way I see it is you gotta blow the cylinder pressure down enough on the exhaust stroke so that it can make use of the overlap to get the most possible intake charge in.

I'm sure if you posted this question in the Naturally Aspirated section some guys who actually know what they are talking about will chime in, lol
Barrett
 

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SBF TTFMF
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It all depends on the combo, is the short answer...

But I have spoken to quite a few cam guys and I've been told you can run more duration in general with a stickshift opposed to an automatic.
 
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