building 500+ whp 98 gsx, suggestions

[elfroggo]

I would rethink that statement that the subaru 2.5L is crap. How did you come to that conclusion? STi's aren't to be underestimated and are very capable machines
Higher displacement will get you better boost response compared to a smaller displacement engine.

from http://www.rsportscars.com/eng/cars/impreza_wrx_sti.asp

300-Horsepower Turbo Engine

The 2.5-liter horizontally opposed (Boxer) 4-cylinder engine is based on a specially reinforced semiclosed deck engine block with forged aluminum-alloy pistons, forged high-carbon steel connecting rods and sodium-filled exhaust valves. The Subaru Active Valve Control System (AVCS) variable valve timing technology helps provide strong torque characteristics throughout the engine's operating range. The turbocharger produces 14.5 psi of maximum boost compared to 13.5 in the standard WRX. The large capacity intercooler uses a manually operated water spray feature to enhance intercooler efficiency during high-performance driving.

 

[Slippi84]

The Evo's are built for one reason rally racing. The WRC mandates a 2.0l engine.

Ahhh this is true I didn't take that into consideration. Good call.

 

[mirkoelek]

I've decided going with 2.4l.... NOw i need some info... where to get a block internals...any other parts ,, should i go with 7bolt 2.4 or 6bolt....should i build block myself or get it from the shop

 

[Turbocharged]

I've decided going with 2.4l.... NOw i need some info... where to get a block internals...any other parts ,, should i go with 7bolt 2.4 or 6bolt....should i build block myself or get it from the shop

http://www.dsmtuners.com/forums/showthread.php?t=100677&highlight=g4cs
http://www.dsmtalk.com/forums/showthread.php?t=31111&page=1&highlight=g4cs

 

[AL92]

You get a 2.4 6 bolt like i have from 89 to 91 hyundai sonatas.You use the block mains and crank and throw the rest away.
If you have a 2.0 6 bolt then would do a 2.3.
I would use the new eagle forged crank if you are going to do heavy track with the car. I got my crank polished only not turned. You don't really want to turn the cranks this can take off nitride hardening and make them more prone to failure.I also will be keeping my rpm limits at 7500 to 8000 tops.

I think the 7 bolt 4g64 or the 6 bolt g4cs or the 2.0 1gs engines would be ok. Just the 7 bolt 2g engines have the bad rep for crankwalk.I would still stay away from them.Far away!!

My 2.4 swap was a lot of work and did cost a bit since did use good parts.A 2g head is easier also .I went with the 1g head, 1g jm fab intake and 1g tb. I bought a spare 2.0 engine for 150 or so US and the 2.4 bottom end for 400 US.My 2.4 had 20,000 original miles on it car was rearended and sat in wrecker all these years.Well engine sat at wrecker.I foound some parts NIB or nearly new cheap. I got crower rods for price of eagles actually less.I used new pricey acl coated bearings .I used new wiseco forged pistons .020 over. Set them at .0035 piston to wall and opened the 1st and second rings to like .019 and second to like .023 as have big turbo and plan small shots of nitrous.
Ross uses much bigger piston to wall like .006 but they measure differently from wiseco.

I also don't believe in fancy headwork since the engine is interference and the heads seem fairly easy to warp from bad overheats.

I used manley stainless valves and manley keepers,got crower springs NIB cheap with the titanium retainers and used crower stage 3 cams very streetable in my 2.4 with not much lope at 1000 and a fair bit at 850 if you like to scare the honda boys.
I used 3g lifters.Reused my rockers . In my build used 2.4 cam gears and 2.4 timing belt.
6 bolt 2.0 oil pan, 6 bolt dipstick and 6 bolt dipstick tube. 6 bolt timing cover modified and you have to cut the 2g motor mount up to fit.

I used 2g water pump pulleys,6 bolt water pump.fluidampr works on 1g and 2g cars it seems.Used 2g power steering pump and air compression moved starter mounting plate over to the 6 bolt.Used 2g starter.



I saved money by getting the machining and bottom end assembly done at machine shop.I did the rest myself.

So far I like the 2.4 but have to fix my current pretty sure clogged cat problem and then car should rip. Right now my car is as fast as a hyundai sonata! Next day or so will unbolt and then cut off the factory cat and have new apexi gt downpipe and catback coming in a week or so. I have check engine lights for failed cat and I have all the symptoms.

If you have further questions about the build you can ask me ,turbocharged is very knowledgeable also. I took a lot of his advice but some things I did my own thing.

One thing I did was dont' believe in any fancy smancy stuff in building an engine.
I didn't balance the crank or any other parts,not flywheel or clutch either.I heard aftermarket parts are close and so is factory crank.
I took out balance shafts for sure,they are the devil,seen engines ruined by balance shaft belt breaking and wrapping around the timing belt. I also seen balance shaft bearings spun out and cause big problems. I used a fluidampr balancer as the factory balancers are garbage and fall apart at random miles. I had two of them fall apart on me causing various degrees of damage.
I have energy suspension rollstop front and back inserts. My car has no noticeable vibration at all zip.nada..The fluidampr really seems to do the job and it should never separate.Worth every penny.

Another thing I did since took out the balance shafts is port my oil pressure relief hole.
I don't like sky high oil pressure which you get from no balance shafts. My oil pressure seems close to normal range for a balance shaft engine.

I have only two regrets in my build that hopefully won't come back to bite me in the ass.
I would have used the new forged eagle crank for extra insurance but it just came out when I had my engine done already and didn't feel like messing around again.I will put one in if every have the engine out of the car and if the engine is ok. I would for sure use one in a 2.3 .They are not that expensive in the big picture. Around 800 US.

Also I would have used kevlar timing belt but they don't make one for the 2.4 yet.

I also was anal and used lots of new parts..new 6 bolt in my case timing tenisioner,tensioner pulley,new tensioner arm the 1g one was badly worn where tensioner pin hits it.,new idler pulley, new mits water pump, new mits front case and new bevelled oil pump gears.New mits therm and the first one I installed was defective and was sticking and car kept overheating but luckily think things are ok.I shut the car down each time right away. No overheating since changed the therm to another oem one.

So don't think oem parts are failure free .Factory is not god.
Also I used mostly topline gaskets for most of the engine from a set and think would have gone mits next time.I have some oil leaks have to fix and might be due to topline being cheap crap not sure. I used topline oil pan gasket rather than rtv for one thing.I may have leaking pan now.

 

[Slippi84]

You get a 2.4 6 bolt like i have from 89 to 91 hyundai sonatas.You use the block mains and crank and throw the rest away.
If you have a 2.0 6 bolt then would do a 2.3.
I would use the new eagle forged crank if you are going to do heavy track with the car. I got my crank polished only not turned. You don't really want to turn the cranks this can take off nitride hardening and make them more prone to failure.I also will be keeping my rpm limits at 7500 to 8000 tops.

I think the 7 bolt 4g64 or the 6 bolt g4cs or the 2.0 1gs engines would be ok. Just the 7 bolt 2g engines have the bad rep for crankwalk.I would still stay away from them.Far away!!

My 2.4 swap was a lot of work and did cost a bit since did use good parts.A 2g head is easier also .I went with the 1g head, 1g jm fab intake and 1g tb. I bought a spare 2.0 engine for 150 or so US and the 2.4 bottom end for 400 US.My 2.4 had 20,000 original miles on it car was rearended and sat in wrecker all these years.Well engine sat at wrecker.I foound some parts NIB or nearly new cheap. I got crower rods for price of eagles actually less.I used new pricey acl coated bearings .I used new wiseco forged pistons .020 over. Set them at .0035 piston to wall and opened the 1st and second rings to like .019 and second to like .023 as have big turbo and plan small shots of nitrous.
Ross uses much bigger piston to wall like .006 but they measure differently from wiseco.

I also don't believe in fancy headwork since the engine is interference and the heads seem fairly easy to warp from bad overheats.

I used manley stainless valves and manley keepers,got crower springs NIB cheap with the titanium retainers and used crower stage 3 cams very streetable in my 2.4 with not much lope at 1000 and a fair bit at 850 if you like to scare the honda boys.
I used 3g lifters.Reused my rockers . In my build used 2.4 cam gears and 2.4 timing belt.
6 bolt 2.0 oil pan, 6 bolt dipstick and 6 bolt dipstick tube. 6 bolt timing cover modified and you have to cut the 2g motor mount up to fit.

I used 2g water pump pulleys,6 bolt water pump.fluidampr works on 1g and 2g cars it seems.Used 2g power steering pump and air compression moved starter mounting plate over to the 6 bolt.Used 2g starter.



I saved money by getting the machining and bottom end assembly done at machine shop.I did the rest myself.

So far I like the 2.4 but have to fix my current pretty sure clogged cat problem and then car should rip. Right now my car is as fast as a hyundai sonata! Next day or so will unbolt and then cut off the factory cat and have new apexi gt downpipe and catback coming in a week or so. I have check engine lights for failed cat and I have all the symptoms.

If you have further questions about the build you can ask me ,turbocharged is very knowledgeable also. I took a lot of his advice but some things I did my own thing.

One thing I did was dont' believe in any fancy smancy stuff in building an engine.
I didn't balance the crank or any other parts,not flywheel or clutch either.I heard aftermarket parts are close and so is factory crank.
I took out balance shafts for sure,they are the devil,seen engines ruined by balance shaft belt breaking and wrapping around the timing belt. I also seen balance shaft bearings spun out and cause big problems. I used a fluidampr balancer as the factory balancers are garbage and fall apart at random miles. I had two of them fall apart on me causing various degrees of damage.
I have energy suspension rollstop front and back inserts. My car has no noticeable vibration at all zip.nada..The fluidampr really seems to do the job and it should never separate.Worth every penny.

Another thing I did since took out the balance shafts is port my oil pressure relief hole.
I don't like sky high oil pressure which you get from no balance shafts. My oil pressure seems close to normal range for a balance shaft engine.

I have only two regrets in my build that hopefully won't come back to bite me in the ass.
I would have used the new forged eagle crank for extra insurance but it just came out when I had my engine done already and didn't feel like messing around again.I will put one in if every have the engine out of the car and if the engine is ok. I would for sure use one in a 2.3 .They are not that expensive in the big picture. Around 800 US.

Also I would have used kevlar timing belt but they don't make one for the 2.4 yet.

I also was anal and used lots of new parts..new 6 bolt in my case timing tenisioner,tensioner pulley,new tensioner arm the 1g one was badly worn where tensioner pin hits it.,new idler pulley, new mits water pump, new mits front case and new bevelled oil pump gears.New mits therm and the first one I installed was defective and was sticking and car kept overheating but luckily think things are ok.I shut the car down each time right away. No overheating since changed the therm to another oem one.

So don't think oem parts are failure free .Factory is not god.
Also I used mostly topline gaskets for most of the engine from a set and think would have gone mits next time.I have some oil leaks have to fix and might be due to topline being cheap crap not sure. I used topline oil pan gasket rather than rtv for one thing.I may have leaking pan now.

It's obvious who doesn't work on saturday

Lots of good info though

 

[pboglio]

Simply put... Strokers are worthless for AWD guys for one reason. if you are really into drag you will have tons of drivetrain problems with 2.3l engines. They cause too much power down below. There are several guys who either are here or on newengdsm who have switched back because they were sick of blowing out axles and xfer cases.

The 2.5l engines are also crap from what I understand. There have been several people with blown blocks from upgraded turbos. Since 2.5l STi aren't using forged internals.

Edit: If that is true I retract my statement but I have heard about various STis blowing their blocks on upgrading to a bigger turbo. If you had an explaination for that that would be great.

As for 2.5l engines. If you can prove that there are 2.5l Stis that have run anything better than the 2.0l Japanese STi or any 2.0l turbo that would be great. Define capable? Capable compared to what we do or capable for that engine? There are tons of STi owners out there and very few that run compared to the EVOs or DSMs. Its another 2.0 vs 2.3. In drag its been proven that the 2.0 is more proven

Ahem, have a read:

http://linux.forcedperformance.net/merchant2/merchant.mv?Screen=CTGY&Store_Code=FP&Category_Code=WRX

Thats plenty capable in my book. I'd gladly swap pistons in my STi once, then have to replace my DSM transmission on an annual basis.