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Discussion Starter #1
I've seen them mentioned several times. Which would everyone suggest. I plan to put them on my stock '74 260. I already have the 2 1/2 pipes, just haven't bought the header yet. It's going on the E88, but will either one fit the P79, P90, P90a? Which would be better for this application? I don't care to much right now about the performance until I get the new motor which will eventually have turbo. It will be a daily driver for this winter, just because I love to drive it. Then it will go in the garage to be broke down. Thanks everyone in advance.
 

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Square port vs. round

The E88 head is a square port, the P79, 90 etc are round port heads with exhaust sleeves. You will have to go with the early model square port header. As far as performance is concerned, that is truly subjective. I don't believe I have seen any dyno specs that lean one way or another as to a 3 into 2 into 1 configuration versus the 6 into 1. The 6 into 1 looks like it would be a pain in the butt to put on a car though. Hope this helps.

> I've seen them mentioned several times.
> Which would everyone suggest. I plan to put
> them on my stock '74 260. I already have the
> 2 1/2 pipes, just haven't bought the
> header yet. It's going on the E88, but will
> either one fit the P79, P90, P90a? Which
> would be better for this application? I
> don't care to much right now about the
> performance until I get the new motor which
> will eventually have turbo. It will be a
> daily driver for this winter, just because I
> love to drive it. Then it will go in the
> garage to be broke down. Thanks everyone in
> advance.
 

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Re: Square port vs. round

> The E88 head is a square port, the P79, 90
> etc are round port heads with exhaust
> sleeves. You will have to go with the early
> model square port header. As far as
> performance is concerned, that is truly
> subjective. I don't believe I have seen any
> dyno specs that lean one way or another as
> to a 3 into 2 into 1 configuration versus
> the 6 into 1. The 6 into 1 looks like it
> would be a pain in the butt to put on a car
> though. Hope this helps.

actually, the p-90 series heads have a square exhaust port. here is the break down.
E-31, E-88, N-42, P-90, P-90A all have round intake, square exhaust ports.
The N-47, P-79 have round exhaust ports with the metal liner.
Stay away from the 6-1 header. look carefully at the collector, all 6 pipes come together in about 2-4 inches. not best for performance, even though motorsport touts it as their performance header. you will not see a competitive ITS car,(stock class for road racing 240's), with the 6-1 header. The nissan motorsports 3-2 header is one of the best out there, but costs nearly 300. So you need to carefully evaluate what you are doing. and actually, for a stock motor, ie no cam, head porting work, etc... the stock manifold works great, matching many aftermarket exhausts. an ITS racer did some extensive testing on the 240 motor in ITS configuration with several headers and the stock manifolds. What he found was rather enlightining. All tests were run against a baseline of the stock 240 motor, stock manifold, 2 1/2 exhaust. they were run on a dynojet chasis dyno with the baseline done each day at the end of the runs.
what he found was the stock manifold was within 2.5 peak hp of the best header. the best header, which was the nissmo one,(with it close to another, out of production header), did have a 5 hp advantage in some of the lower ranges,(this was the large diameter header).
Anyways, for a mostly stock motor, the stock exhaust manifold is excellent, just port match it to the head and gasket, and you will be very pleased. when you start getting cams, and larger carbs,(ie triples), then you need some form of header.
if you really want a header, stick with a 3-2. there are lots out there, and unless you spend the big bucks for the nissmo, they will all net you about the same.
-hope this helps. if you have more questions on heads or compression ratios, check out my P-90 page and compression page, on the link below.
-bob hanvey
 

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Discussion Starter #4
Re: Square port vs. round

Thanks Bob. I have your site as one of my favorites and read it on a normal bases, over and over again. I'll probably stick with the stock manifold for the time being, until the big mod(the works) I still getting the whole scoop on all the applications and modifications that are out there. Thanks for all the help and future help that I will need. Z ya
 
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