What is the better route to go?
I could order a JDM FXT motor and have Wiseco forged pistons put in it or I could get a USDM STI block and have Wiseco forged pistons put in and combine that w/ V8 heads.
From what I've found, both options will be comparably priced.

you can find the usdm sti motor for 1650 and cp pistons for like 430 and if they are drop ins for a new motor 130 to install the pistons or 300-350 for some for a hone ,and install :D worldone sells the sti motors with the forged pistons in them for 2450 :)

you can find the usdm sti motor for 1650 and cp pistons for like 430 and if they are drop ins for a new motor 130 to install the pistons or 300-350 for some for a hone ,and install :D worldone sells the sti motors with the forged pistons in them for 2450 :)
Thanks for the info. I am aware that many vendors are selling built blocks. Andrew @ Gearboxtech and his machinist will be doing all of my work.
Both options will have Wiseco pistons in them. (I'm not going CP for various reasons).
The question is, will the JDM V8 heads on a built 2.5 be a better choice than a JDM FXT motor with a built bottom end?
Thanks for the help.

So the shortblock on either 2.5 will be getting forged pistons, so they are going to be equal.

The heads on the V8 should flow better than the stock 2.5 heads from what people have reported on here (never flowbenched any personally).

If it is true that the 2.0 V8 heads > USDM/JDM 2.5 Heads then it should be an easy choice :)

Yeah... if the 2.5 w/V8 JDM heads is going to have pistons then that's the way to go. Those heads are big port.... and will give you all the loven sweetness.

If you can get some Jun 274 in it you'll be ready to really crack open the boost. I would just check into the inspection in MD.... it may or may not be an issue.

Yeah... if the 2.5 w/V8 JDM heads is going to have pistons then that's the way to go. Those heads are big port.... and will give you all the loven sweetness.

If you can get some Jun 274 in it you'll be ready to really crack open the boost. I would just check into the inspection in MD.... it may or may not be an issue.
Thanks for the input. The cams sound sweet for the high end but I'm looking for low end grunt and will not be running AVCS, at least initially.

To bad Perrin doesn't have there H6 project matured yet. http://forums.nasioc.com/forums/showthread.php?t=959768

That thing is going to be a torque beast.

I have this Set-up Ver 8 heads, 2.5 block, Billet rods, Knife edged crank shaft, Weisco pistons. Compression 8.5-1

I haven't had this engine tuned to its full potential as it has been broken in. One thing i can tell you that you will need to keep the compression 8.5-1 or lower on pump gas so i believe you will need custom pistons for that.

Any more info i will gladly help :)

Oh and the AVCS is a no brainer if you have the ECU too.

I'm thinking that the only detractor now is if your still running the stock 02 tranny in that car.

I'm thinking that the only detractor now is if your still running the stock 02 tranny in that car.
Not quite :)
PPG Straight Cut 1-2 Helical Cut 3-4
STI Helical front diff
Kaaz 1.5 way rear

I would go with the JDM FXT engine.. more low end torque can be had because of the added compression. And the heads flow slightly more up top.

I would go with the JDM FXT engine.. more low end torque can be had because of the added compression. And the heads flow slightly more up top.
Are you saying the JDM FXT heads outflow the V8 heads? I thought it was just the opposite.

No the FXT heads flow more up top but flow a little less during midrange lift.

Thanks for all the help guys!
I'm going V8 heads with a built 2.5 bottom end.
WRX intake manifold and TGV deletes.
GT30R .63 A/R.
I hope to get 250whp on race ;)

make sure you get RA Spec C v8 heads. those are the ones with the big port. those heads are totally bitchin', best heads ever. finally something that can stand up to the 4g63 heads. haha.

What is the better route to go?
I could order a JDM FXT motor and have Wiseco forged pistons put in it or I could get a USDM STI block and have Wiseco forged pistons put in and combine that w/ V8 heads.
From what I've found, both options will be comparably priced.

It appears that you've already made your decision but you might be interested to know that the JDM FXT motor and USDM STI motor are internally identical. The JDM ver. 8 heads do outflow the USDM STi / JDM FXT heads at points but they are closely matched. As has already been pointed out, many companies sell prebuilt shortblocks w/ forged pistons. Ours uses Wisecos and also replaces the bearings w/ coated race bearings because we feel these are nearly as important to replace as the pistons. The price is still very close to other companies built blocks with only forged pistons.

Thanks for the input. The cams sound sweet for the high end but I'm looking for low end grunt and will not be running AVCS, at least initially.

If you want low end grunt then you should run the AVCS. The AVCS really fattens up the midrange torque band. Running without AVCS will leave the cams in high-lift mode which is good for upper end power but no for mid-range and low-end power.

Thanks for all the help guys!
I'm going V8 heads with a built 2.5 bottom end.
WRX intake manifold and TGV deletes.
GT30R .63 A/R.
I hope to get 250whp on race ;)

That's an excellent combination. I think you'll be very happy with the results; good spool up and good power. You should be able to hit about 475 CHP (well over 250 WHP on any dyno) on 100 octane with that setup.

-Geoff

Thanks for the info Geoff.
Yeah...I was joking around about the 250 whp figure. TurboXS will be taking care of the tuning.
93 Pump Map (hoping 375 whp)
93 Pump Map w/ alky (hoping 425+ whp)
C16 (hoping 450+ whp)
We'll see. The car should be up and running in late May.

Any reason why the 30r instead of the 35r?.

Thanks for all the help guys!
I'm going V8 heads with a built 2.5 bottom end.
WRX intake manifold and TGV deletes.
GT30R .63 A/R.
I hope to get 250whp on race ;)

:lol:

250whp @ 3500rpms!!! If your tuner doesn't get at least 100whp more on pump gas, get a new tuner.

Any reason why the 30r instead of the 35r?.
Useable power. (Street and AutoX use).
I don't want a violent surge in power at 4000 rpm.
I don't want to break axles.
I don't want to break the R160 rear end (although it has a Kaaz 1.5 way in it).
I want to use an ACT street/strip clutch and not a 6 puck.
Something different.
Just a few of the reasons.

:lol:

250whp @ 3500rpms!!! If your tuner doesn't get at least 100whp more on pump gas, get a new tuner.
Yeah...I live 25 minutes from TXS in Gaithersburg MD. I think they should know what to do by way of tuning ;).

Just so you know, the tuning tools:
UTEC
Tuna PRO
DTEC BC w/ Knocklite
EGT Gauge

Is this combo running now? I would be very interested in it!

We have two full V8 STI big port heads coming back to us by monday, and we have the JDM EJ257 heads in stock. The EJ257 heads ultimately have more potential as they flow more, have larger compression areas, and coupled with some good porting, valves, valvetrain, and cams will make more power (but are pricier)

Cheers,

Gary
Gruppe-S

Is this combo running now? I would be very interested in it!

http://forums.nasioc.com/forums/showthread.php?t=1087350

I haven't had this engine tuned to its full potential as it has been broken in. One thing i can tell you that you will need to keep the compression 8.5-1 or lower on pump gas so i believe you will need custom pistons for that.

why is that?...nevermind forgot you are on 91...
I was going to say a properly done 9.0-9.2 @ 20psi on 93 isn't a problem...you guys need to look at quench height and pad a bit more ;)

edit: thought the thread looked familiar...so old