WRX 2.5 STi short block hybrid swap

K

Killerbumblebee

New member
hey all,

I blew on of the rod bearings in my engine last week...I don't know if I'm going to just get a used 2.0 and drop it in, or try for the 2.5 short block. couple questions:

1. will the stock WRX wiring harness work with the 2.5 STi short block

2. does anyone know where to get one at a good price

3. has anyone done this swap? if so, please PM me, I have a lot of questions conserning what if anything makes it difficult. I'm not planing on running a ton of power through it, I just want the 2.5 for faster spool and better torque, sense I have to fix it anyway.

thanks a ton guys...I'm hoping to get my yellow monster back up by september
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Check out http://www.eastcoastswappers.com They do all kinds of swaps and speciality job.

As far as putting in a 2.5 in a rex, I THINK you don't need a new harness. Don't quote me on that.

If I was you I'd just build a bomb proof 2.0 with all sorts of forged internals and other goodies.

You're best bet is do a bunch of searching on forums like NASIOC.com

P.S. are you the yellow rex in Biddeford?

 
recently faced same choice when rod brgs went on my 02 bugeye wagon.

considered the 2.5 shortblock, but opted for stock shortblock because the larger motor would require a bigger turbo to run right, plus custom wiring, plus who knows what all else.

so unless you want to convert your daily driver into a "daily tuner" stick to stock block.

I got a good price on 2.0 shortblock from Belknap Subaru in NH, their website is subaruxtras.com

used 2.0 is probably simplest/cheapest option, I went with new block to be sure I didn't swap one problem for another. LOTS of work to rebuild the motor, even w/fresh shortblock. car was down a month.

Dave G

PS--even with factory shortblock, you are looking at a BIG job here, good luck. would you be doing work yourself or having it done for you?

PPS--factory shortblock requires re-use of your old oil pump and oil filter/cooler ass'y....make double-triple-quattro sure you get these parts cleaned out well, or you'll just introduce burnt bearing bits into your nice new motor. ALL oil passages need to be cleaned in heads, too.

 
my friends dad is a mechanic, and the three of us are going to be doing the block swap. I'm going to get a new oil pump for the car, I don't want to play around with that. I think the water pump should be fine with some clean up. while the motors off, I'm going to put a new clutch in, and put a rebuilt ported and polished TD04 in (I like the fast spool up of the TD04...does anyone have any sugjestions in a ball bearing turbo with similar spool chararistecs...that is the only upgrade I'd actually consider). and probably high flow headers as well. I'd like to put forged internals in, but I am not that mechanically inclinged (not to rip apart the actual block that is). the only other possibility is if anyone knows someone who would privatly tear down my engine and rebuild it. the second it started making bad noises I turned it off, and the engine never stoped functioning...but it made a bad knocking sound from between 2500-2800 RPM's. the engine only has 39K on it...but before I think about that I'm planing on draining out the oil, seeing if there is anything bad and icky in it, and having it tested. hopfully that will give me some idea how badly damaged my engine is. oh, and I live in portland, my car is yellow, with a dark greay hood and rear spoiler. thanks guys, any more sugjestions would be awsome

 
dont worry about the mechanical aspect of the sti block, its the tuning that's the bigger issue.

the sti block is the same dimensions/bolt pattern etc of your 2.0 block. swapping one instead of the other is no different.

using the sti heads woulld be a pain, but just the block requires nothing special.

not even a turbo. yes the td04 will be far too small for the displacement, but it will still work. it will probably need to be set a differnet boost level and will probably trail off in boost even faster than it does now, but you'll have the extra power of displacement to make up for that.

one concern about a used sti block is buying one that's not blown. if you do get a used one, bring it to a engine builder to get checked over. the bearings, and most commonly the pistons/rings (on cyl 3 usually) are the biggest problems. you can get a brand new sti shortblock from subaru for somewhere around $1600

once the motors in there, you would need to have engine managment of some sort. something totally tunable like utec would be good, but an safc or something to bump up fuel across the board might suffice. dave at http://www.f1dyno.com in portland would know. this is because you have more displacement pulling air in, you need more fuel as well.

silverbqqst on here or dave would probably know the most about IHI series turbo selection, bqqst's been through a couple differnet ones on his sti.

p.s., i've got 2 td04's for sale in that forum if you need an extra one to port.

 
the second it started making bad noises I turned it off, and the engine never stoped functioning...but it made a bad knocking sound from between 2500-2800 RPM's. the engine only has 39K on it...but before I think about that I'm planing on draining out the oil, seeing if there is anything bad and icky in it, and having it tested.

any more sugjestions would be awsome
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suggestions? get your friend's mechanic dad to give the car a good compression/leakdown test so you KNOW what you are up against. that knock could be half a dozen issues...rod bearing, bent valve, dropped valve guide, piece of busted plug in cylinder, etc etc. Is there oil in the coolant, or coolant in the oil, brass bits in the sump, yada yada yada. you basically have no idea at this stage what is really the problem.

you'd be nutz to tear down a motor without having at least an informed idea of what problem you are chasing. until you have a better idea, "suggestions" are not much more useful than blowing smoke.

final suggestion is, "keep it stock" unless you want to spend lots more time and $$$ troubleshooting half-baked mods. mods to a WRX are not as 'simple' as ppl on scooby boards would like you to beleive, do you REALLY want to experiment on your own car with your own money when somebody else is doing the work???!!!

if you want mods, go to F1Dyno. you want stock, have your friends' dad do it.

Dave G

 
the good thing about the sti block swap is that half a million people have done it. there are a number of proven setups out there, with dyno numbers and such to give you an idea of what you're looking for. the tunes will be different for each car, as always, but you should leave f1 dyno to that.

 
I already have a fully adjusable Turbo XS utec in the car (and dave from F1 was the guy who put it in :-) I'm going over to my friends house today, and we are going to drain the oil out of it. I'll also check the spark plugs while I'm at it to see...but I would think that if one of those had broken off, the engine wouldn't still be running pretty normally after it happened ( - the noises ). Thanks for all the help guys. If I do do the 2.5 swap, I plan on putting it in myself, and then having D1 set it all up...I don't play around with that stuff...I just can't afford the 1500-2000 instalation on the engine. the only other thing I will mention is that I had just put on the performance perrin pully (lightened, but not underdriven). could a timing error have caused this at all? thanks guys, all the help is much appriciated.

 
the only other thing I will mention is that I had just put on the performance perrin pully (lightened, but not underdriven). could a timing error have caused this at all?
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The pulley you put on doesn't change the timing, it only drives the Alternator, AC and power steering.

 
If I do do the 2.5 swap, I plan on putting it in myself, and then having D1 set it all up...I don't play around with that stuff...I just can't afford the 1500-2000 instalation on the engine. the only other thing I will mention is that I had just put on the performance perrin pully (lightened, but not underdriven). could a timing error have caused this at all? thanks guys, all the help is much appriciated.
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KBB--your last question raises a big red flag. not about if the pulley caused the problem (unlikely) but if you don't know the answer to that already, how can you expect to handle installing a swap yourself? A short block swap requires complete dissasembly of your old block and transferring every part except for pistons and crank to the new motor. Unless you've done major motor work before, the complexity of this task will blow your mind. You need to get everything taken off the old motor in precise proper sequence, tagged, organized and stored, then reassembled in sequence, torqued and adjusted right--first time--or you are likely to cause big problems with poor running or even significant damage to parts not installed/tuned/interconnected properly.

you mention doing the mech work and then having F1 "set it all up". Well, they often get cars in to "set it all up" after owner mods or mech repairs or swap installs. The news there is almost universally bad--grounds hooked up wrong so ECUs and senders are cooked, bad vacuum connex so the cars barely run, botched turbo upgrades, exhaust nightmares, clutches/AC/other ancillaries installed wrong or maladjusted...etc etc. all of this stuff costs cubic money to rectify after these badly installed parts cause problems further down the line. If you can't afford the couple grand to pay a pro to do your swap, you sure as sheet can't afford to pay F1 to straighten out a major mess either.

you CAN learn as you go, but expect to spend probably 3x the time you think it will take, and be prepared for significant expense to put things right after you THINK you're "done"

DG

PS--what did you find with initial engine condition checks?

 
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