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Old 07-08-2008, 12:27 AM   #1
methaddict
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2004 WRB STi
Full Race TS, BW 8374 EFR

Default Supertech valves choices

black nitrided or inconel? standard, .5mm larger or 1mm larger.

Supertech recommends inconel valves for turbo applications. The inconel uses a 751 nickel alloy for high heat. This must be good for nitrous, forced induction applications.
I know black nitride gives the valves a better hardess and also reduces valve guide friction. So this must be for higher reving applications.
Which one? With all the oiling issues I don't know if I want to raise the rev limit. I won't be using nitrous either but it is definitely turbo. I'll have a gt3076r, which would be the best choice.


Will going larger .5 or 1mm valves lose velocity which will inturn lose torque?

My builder recommends doing a 3 angle valve job, any input on this. I've read some like to do a dual radius for less swirl.
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Last edited by methaddict; 07-08-2008 at 01:11 AM.
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Old 07-08-2008, 11:10 AM   #2
fobiawrx
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i went with the inconel valves and 1mm over. im looking to flow more air threw my heads so went with bigger valves. just because you can rev higher doesn't mean you have to too.
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Old 07-08-2008, 11:14 AM   #3
jaxscuby
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0.5 for intake
1.0 for exhaust
inconel
valve jobs
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Old 07-08-2008, 12:09 PM   #4
charliew
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If the build of the motor only makes the power at high rpms, thats where you will be using it.
Larger valves are for higher rpms as are higher lift cams.

If you are happy with 350-375whp then the stock valve sizes will work and give better low rpm torque, I'm not sure exactally where that hp number falls, depending on the boost.

Most stock size valve motors even with better cams giveup the power at below 7k.

Multiple angle valve jobs always help flow, usually the low lift area shows the most improvement, at least that's what I have read. As someone already posted the valve spends twice as much time in low lift as high lift.

We flowed some ported heads before and after a performance valve job and really didn't see much improvement but will still go for a multiangle job every time.

I would buy the best valves I can afford. As in: iconel, backcut, and coated, these things all help the valves live longer in a turbo application.

Last edited by charliew; 07-08-2008 at 12:23 PM.
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Old 07-10-2008, 12:29 AM   #5
methaddict
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I'm not doing any port work so as to not shift the power band to the right. I am installing BC 272 cams and Supertech dual valve springs, ti retainers and alloy seats to keep from floating a valve. They will be doing a 3 angle valve job.

A couple options I'm considering. For the heat cycles the exhaust valves may endure I may just get the inconel standard size exhaust valves and keep the stock intake valves. I'm close to my build budget limit so if I can do both inconel exhaust valves and the black nitrided intake valves I will. But if I can only do one side would the stock intake valves be ok. Staying stock size to keep power band from shifting to far to the right.

I'll either be going with the AVO twinscroll garrett hyrbrid gt3076r cartridge or the ATP stock location gt35r so you'll know what the characteristics of the turbos will be.
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Old 07-10-2008, 10:53 AM   #6
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Hogging out the runners will shift power to the right, but basic blending and smoothing typically yields power accross the whole RPM range.

I'm porting my heads myself and I'm going pretty mild. I plan on putting some time into the doglegs to even out the exhaust flow, but most of my work will be in the chambers. I'm opening up the 2.0 heads to the 2.5 bore and I'm unshrouding the valves. Unshrouding the valves makes a big difference at low lift and typically adds low RPM power. I'm also knife edging the intake dividers and blending the bowls, but mostly it'll just be smoothing.

As far as valves go, I went with stainless .5mm oversized for intake and exhaust. I run E85, so Inconel would be a waste of money for me. If I were running gas and on a budget, I would keep the stock intakes and upgrade the exhaust to stock or .5mm over Inconel. The cams are going to affect your power band much more than mild porting or valve sizing will.
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Old 07-10-2008, 01:28 PM   #7
kellygnsd
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By how much does E85 lower your EGT's by blue?
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Old 07-10-2008, 02:09 PM   #8
bluescoobywagon
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With lean mixtures and tons of timing, I never saw over 1550 measured where the runners come together on the driver's manifold. I was really pushing the limits of the high RPM power on my TD04/2.0L and had 250 hp+ from 4700-7000 rpm.



When I first switched over, my EGT's were 100-200 cooler than gas at redline. I actually had problems building enough exhaust energy to maintain high boost pressures from 5000-6000 rpm and had to do quite a bit of tuning to get the lost power back.
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Old 07-12-2008, 03:08 PM   #9
methaddict
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Well I'm ready to order both black nitride intake valves and inconel exhaust valves. For an 04 sti block, no port and polish, bc 272 cams, Supertech dual springs ti retainers and alloy seats, 3 angle valve job, should I go std, .5 over, or 1mm over? How much more will 1mm over shift to the right.
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Old 07-30-2008, 01:39 AM   #10
methaddict
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Well, I just ordered standard sized Supertech black nitrided intake valves and std size inconel valves. Portflow will be doing my valve job which will have a 45 degree closer to the edge then will go into a radius. I just don't want to move the power band more to the right than the BC 272 avcs cams will do already.
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Old 07-30-2008, 10:21 AM   #11
bluescoobywagon
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That should be a great setup.

Since I autocross, I'm always worried about loosing too much low end. My 2.0 made 200lbs of torque at 3,000 rpm and my goal is to beat that by 25-50 lbs with the 2.5 hybrid. As long as I don't go under, I'll be happy.
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Old 07-30-2008, 12:44 PM   #12
kellygnsd
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You should crush that goal Blue with the 2.5L. I'm making 260 ft-lbs at 3100 rpm on a mustang dyno with Cosworth 275 cams, +1mm valves, and an 8cm^2 18G
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