twin turbo heads

[azn2nr]

looking at these http://forums.nasioc.com/forums/showthread.php?t=859945

and am wondering if it would work. that manifold is the same that my friend noah has on his car and he is running it on a ss ecu. the only problem is what about the rest of the heads. other than the fabricationg on oil suply and coolant return i dont think it should be a porblem, maybe oil return needs fixing but hopefully not.

[BAC5.2]

You can use those, sure. But I wouldn't.

Shim over bucket = bad news bears. At high RPM, the shims like to shoot out and when that happens, kiss your motor goodnight. The worst part is, that there is no warning or anything. Just POP. And there isn't even an RPM threshold. It could happen at any time really. If a valve spring isn't in 100% great shape, BAM, goodbye.

You could convert them to shimless buckets, but you'll tack $800 onto the price of the heads to do so. Each shimless bucket costs $50 from the dealer, and you'll have to measure to the thousand of an inch to make sure you get the right one. It's tedious.

For coolant return, you could just interupt any of the coolant lines from one side of the motor to the other, as long as it is a pressurized line, you can stick the turbo between it.

Oil, you could probably use the stock supply line, and have it dump to the stock return spot, and block off that port on the other head.

Possum Bourne is a good shop though. They ported and polished and rebuilt my turbo.

[555BCTurbo]

I saw Possum drive at Rally New Zealand before he got killed...man...he kicked ass!

Sorry to hijack

[Matt Monson]

I wouldn't be so quick to disregard those heads because of the shim over bucket design. That is the same design that was used on all WRX heads from '97 up until '03. It is an excellent design. Shims are not known for spitting at anything below 7500rpm. It happens, but it is rare. If it was a major issue, Subaru wouldn't have produced them for so many years.

If you can get those heads for $300-400 with manifold, I would consider it a good deal...

[azn2nr]

ohhhhh so tempting. does anyone know the flow rate of these heads

[BAC5.2]

I wouldn't be so quick to disregard those heads because of the shim over bucket design. That is the same design that was used on all WRX heads from '97 up until '03. It is an excellent design. Shims are not known for spitting at anything below 7500rpm. It happens, but it is rare. If it was a major issue, Subaru wouldn't have produced them for so many years.

If you can get those heads for $300-400 with manifold, I would consider it a good deal...

They stopped them mid-02. We have the heads from a late production 02 going on a built 2.5L shortblock, and they are of the shimless bucket design.

One customer had one of the first WRX's in the country and now has 145,000 miles. Shot a shim out and destroyed the motor. Stock for its entire life, blew one transmission and popped the motor. And it was purely a daily driver.

If I was leaving it stock, fine, leave the shims. Any modding, and I'd hate to worry about something that COULD, but doesn't mean it WILL happen. Espically something that is easy to fix (though expensive). You can eliminate all issues with this, by using shimless buckets, but that adds money.

It could be a good deal. But I still wouldn't run anything with shims if I was going for lots of power. Just my .02.

[Matt Monson]

Well,
To me, one example of a high mileage car doesn't suddenly make it an issue. Who is to say that his didn't spit the shim because he never serviced his heads in 145k mi and didn't bother to check the spec. That's why people are supposed to adjust their valve lash at service intervals.

I know a lot of guys here in Colorado, Xephyr included, who have run shimmed heads with silly amounts of horsepower and boost with ZERO problems. These are cars that make double or triple the power than a stock WRX. From everything I have ever seen, shims spitting on performance builds are about rpms and not a result of any inherent design flaw. It is a pretty well known fact that if you rev to 7500 rpms or beyond, they will spit. But the guys around here that run to 7200rpm on 20+psi of boost have zero issues with them. Is the shimless design better? Sure. Is the shim design bad? absolutely not!

[azn2nr]

doesnt dzx have shims in his heads???

[Matt Monson]

doesnt dzx have shims in his heads???

Those are different. Those are shims you place under the HLA's with the reground cams. It is impossible to spit those shims, and the HLA's still provide the valve lash.

The shim over bucket heads are using the shims to adjust the lash for you...

[BAC5.2]

They stopped using them for a reason, right?

All I'm saying, is that if I'm going to invest money into a built motor, I'd rather start with something that already has the shimless buckets, or convert a shim-over-bucket to a shimless bucket.

But then again, I want a higher redline.

[evolutionmovement]

Not familiar with the Subaru heads, but it sounds like the spitting issue is really down to the springs. If it's a problem with higher (than recommended?) rpm or age it would be down to valve float. This is a big reason why older exotics needed very frequent valve lash adjustments and checks - high rpm/high cost motors.

Steve

[BAC5.2]

Factory US-Spec WRX redlines at 7000.

[irishsetter]

Can you fit these heads in a 91 ss with ease?