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Old 06-02-2010, 02:43 PM   #1
Scooby Specialist
Member#: 106909
Join Date: Feb 2006
Location: Essex-England-United Kingdom
2002 V7 STi Prodrive
Edition... Black!

Default Limits of stock JDM v8 cams/valvetrain?

Currently have a 2.5 build underway to be fed by a GT3076R .82.
I am using JDM Sti 8 heads with modified combustion chambers to suit the 2.5 bottom end. The cams and valvetrain are currently stock.

Can anyone tell me where will i hit the wall with the cams/valvetrain on this setup?

And if i was to swap to a GT3582R would the cams/heads flow enough to make mid 500's?

Just interested to hear some experiance/opinions on where my next limits will be?


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Old 06-02-2010, 03:03 PM   #2
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Join Date: Feb 2001
Location: Dublin, CA
2002 WRX Sedan
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Flow limits are somewhere around 10% higher than a stock ej255 / 257 head. I say this because you can find a fair amount of stock ej255 / 257 charts in proven power bragging to use as a guide that you will be capable of at least as good as that.

For example, This is a plot from a stock location GT35 with a billet wheel on a car with stock heads (460 WHP):

So, you'll probably be real close to 500 WHP with some better heads. the time attack cars running the GT35 or billet GT35 are all with headwork and intake manifold work and they show 550+ WHP. I'd expect you to end up somewhere right around the 500 WHP area. UK tends to use BHP, which I think ends up higher than the WHP you'll see from US graphs, so your baseline may be different from the numbers here.

I think those heads would be a real nice match for a GT3076R. On a GT35, they will be some restriction, but I don't think it's a terrible restriction. you'll still get some good power from a GT35.
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Old 06-03-2010, 09:44 AM   #3
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2000 Outback Limited


the stock heads aren't good enough by themselves. need at least cams, but proper head work and a proper tune would be helpful.
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Old 10-11-2010, 04:45 PM   #4
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Reviving an old thread but the big port V8 heads are excellent, both with flow and valve train.
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Old 10-12-2010, 12:50 PM   #5
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The stock cams don't offer nearly enough lift to support a true 500WHP setup. Heads are OK with only a little bit of work but JDM V8 cams are less than 9 mm lift! You can rev the hell out of it but you need a better lift profile with a 3582.

I would suggest modest duration and big lift, >10.5 mm, custom cams if you are going to keep it a DD. Go all out on duration if you have an off-road application in mind.

You're also going to need valves, springs and retainers with high lift cams...

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