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Old 10-26-2009, 09:16 PM   #1
mlangejan
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Lightbulb 2.5 sohc na heads

just wondering if anybody has actually flow benched a set of these heads and has numbers to go with them. i've heard claims of them out flowing dohc STI heads and flowing as much as the chevy LS1. i ported mine and i noticed a little difference but i also did a bunch of other things to the engine as well. i never had them flow benched so i do not know if it actually did anything.

this is all i figure that the claims are based on is that a na motor relies on volume metric efficiency of the engine as a boosted motor relies on the force of the incoming air to enter the engine so the ports in a na motor would be bigger to get the most out of the engines ability to suck and blow
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Old 10-26-2009, 09:18 PM   #2
Matt Monson
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Nope. Never been done. Not once.

I've never posted my numbers either.
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Old 10-26-2009, 09:23 PM   #3
Burnout
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Old 10-26-2009, 11:34 PM   #4
VIsubi
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more than a LS1 motor..hmm doubt that but yeahthey flow more than the DOHC's personally built SOHC heads are wicked with boost..port and polish with angle job good be a beast of heads.
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Old 10-27-2009, 12:13 AM   #5
williaty
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Mine are out for flowbenching now. When they come back, the porter and I are going to work out a plan for making the heads work with the cams I've finally settled on. Hopefully, within Q1 2010, I'll have PnP'd heads with cams, valves, the works.
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Old 10-27-2009, 10:07 AM   #6
Matt Monson
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Quote:
Originally Posted by VIsubi View Post
more than a LS1 motor..hmm doubt that but yeahthey flow more than the DOHC's personally built SOHC heads are wicked with boost..port and polish with angle job good be a beast of heads.
It was Cobb who published that information. They used to work with Chapman and used to have a graph on their website that showed LS1, Ej22t, Ej25D and Ej251 all side by side. So you can doubt it, but I'll take Trey Cobb's word over yours on this subject.
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Old 10-27-2009, 11:07 PM   #7
VIsubi
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so ur saying two n/a motors and our heads flow better and more air that makes no sense then why dont more wrx's install sohc heads with boosted applications then anways whatever.
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Old 10-27-2009, 11:13 PM   #8
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Cobb like a billion years ago posted flow numbers.

It can be found through the Way Back Machine ala www.archive.org

I made it easier by actually copying both the SOHC and DOHC articles into a Word doc and uploading it.

http://www.gigafiles.co.uk/files/185....5L%20SOHC.doc
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Old 10-28-2009, 12:09 AM   #9
williaty
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Quote:
Originally Posted by VIsubi View Post
so ur saying two n/a motors and our heads flow better and more air that makes no sense then why dont more wrx's install sohc heads with boosted applications then anways whatever.
Because it's a pain in the ass to get the SOHC heads to work with an ECU that's expecting a DOHC setup. Then, with the advent of AVCS, it became and even bigger PITA. Frankenmotors are rarely simple.
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Old 10-28-2009, 10:28 AM   #10
Matt Monson
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Quote:
Originally Posted by VIsubi View Post
so ur saying two n/a motors and our heads flow better and more air that makes no sense then why dont more wrx's install sohc heads with boosted applications then anways whatever.
Do a search for Wedge's build. Also look for Xephyr's build. Both cars in the 400whp realm running SOHC Ej25 heads. But they were both done on the GC chassis.

I suspect that over time you will see more and more new age 2.5i's slapping their stock SOHC heads onto Ej257 bottom ends and boosting them. With the option to OS tune them now, boosting is a viable option on the modern cars in a way that it wasn't before. You just won't see it on many WRX's or STi's. They'll stay DOHC.
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