Help please 2.5 sti block with 2.0 wrx heads
 

Hi All quick one if I may.


Thanks in advance, any help is very much appreciated.:wonder:

Really keen on buying this 55 plate wrx turbo saloon with a 2007 sti bottom end. The car obviously came with the 2.0 litre engine from new which had covered about 93,000 miles when the engine started chattering with big end bearing failure. The engine was then removed & the heads split from the block. The owner put the car into to Scooby Technics Fleetwood Blackpool where a short motor from a hatchback 2007 STI which had only covered 15k from new was fitted to the car along with the original heads from the 2005 2.0 litre WRX. Also the following modifications/upgrades were made at the time of the short motor change out. This is a cut & paste directly from sales add detailing the specs as follows.


2005 subaru impreza wrx with 2.5 sti engine

Svf35 turbo

Sti intercooler

Sti blue injectors

Uprated walbro fuel pump

Sti decatdown and up pipe

Miltekcat back exhaust system (left 1 cat in for mot purposes)

New engine has only done 15500 miles. It still looks new.

All fitted and invoiced by scooby technics only 500 miles ago. Timing belt, full service, auxiliary belts, head gasket. All done at same time. All invoices present and service history.

Dual map with anti lag and launch control done by Andrew Carr. Although there is no lag there at all because of the 2.5l engine instead of the 2.0l

Very veryquick with 2 map settings it can be tamed down to 300bhp for economy and turned up to 350bhp for a bit more fun.

It's has a standard clutch so is on its limit at 350bhp. When being remapped Andrew said it would easily go to 380bhp. But needs a stage 1 clutch for that. Personally I don't think it needs to be any more powerful than it is.

Back to me

My worries are (thinking out loud here).:cuckoo: I would assume that this 2.5 sti motor when paired with it’s original heads came with AVCS?

Again I assume the reason they used the old 2.0 litre heads was so there was no need to change out the wiring harness & ecu – Would this be a correct assumption?

Could there be possible problems running these 2.0 ltr heads (non avcs type) that have covered 93K with the newer 2.5 ltr sti bottom end? & the original ecu?

Is the higher 350 bhp safe to be running through the old 2.0 litre gear box which has covered 93 k? Are there any problems with running the sti flywheel, friction plate, pressure plate & thrust bearing with the 2.0 ltr gearbox? Basically do the 2 mesh together harmoniously as if it was the original 2.0 litre motor that was paired with the gearbox & can it handle that power safely as the standard 2.0 ltr wrx was running about 225 bhp ?

Is the 350 bhp safe through the 2.0 ltr drive train? diffs, propshaft, driveshafts etc?

Has Scooby technics in Fleetwood, Blackpool a good reputation as they :top:carried out the work of bring the 2 engines together? I can’t find any info on them.

Note that Andrew Carr carried out the mapping & on the due diligence I have done he has a very good name so no worries there.

Really want to buy the car but just a little unsure because of all of the aforesaid.Again a little point in the right direction would be greatly appreciated.

Cheers Paul :thumb:

that's a well trodden path for a WRX, done that myself.
It would be good to find some feedback on Scooby Technics as that would give reassurance on the build.
Whilst the clutch might be on it's limit BHP wise, the torque would really test it as I suspect it must be in the 360-380lbs/ft and it will probably slip under full load. Not a deal breaker but you may have to upgrade eventually.
Trev

As above plenty of people have put 2.0 wrx heads onto a 2.5 block with excellent results. Won't do 380bhp on vf35 tho
U will find that the torque of the 2.5 will wear out the standard clutch fairly quick so just budget for another clutch in near future .

Thanks for the info Trev much appreciated. Have run my old faithful 1999 V5 uk turbo since it was 6 months old (long time :luvlove:) & had the engine out & in a good few times including full engine rebuild ( 131 K big ends on #3 cyl) & on an other occasion to change clutch friction plate, pressure plate, thrust bearing & flywheel pilot bearing so that wouldn't be a problem for me to do the work. It would just cost me the price of the uprated clutch kit.


So I am assuming that the gearbox & drive train that accompanied the original 2.0 ltr motor in the 55 plate wrx can handle the 350 bhp safely then?:cuckoo:


Cheers Paul:thumb:

Thanks for the info B9SLJ much appreciated.


So would it be a stage 1clutch kit that I would need to purchase then?


Do you know if the gearbox & drive train that accompanied the original 2.0 ltr motor in the 55 plate wrx can handle the 350 bhp safely then?:cuckoo:


Cheers Paul:thumb:

Yeh ty754vn6aa or might be 7aa gearbox is at its limit at 350bhp,the early boxes before 2002 tended to strip the teeth off wen launched hard. I ran approx 340ish bhp for a while no problems on my car was still perfect wen I changed gearbox for 6 speed.
I'm on 6 speed now as I'm running 400ish but still have wrx rear diff hubs and shafts which have coped fine in last 12 months with launch control and some harsh driving to go with it.
Stage 1 clutch such as exedy pink box should be more than enough to handle the torque from the vf35 in your car

Thanks for the info B9SLJ much appreciated.


Cheers Paul:thumb:

As above, 2.5 block onto 2.0 heads is fine as long as its done correctly. My only concern would be it still has the sh!te pistons in from what you've put.

As far as power claims, 350bhp on a 2.5 should be heading toward 380-400ftlb, that will easily see off the 5 speed. Torque breaks gearbox's, not power.

Personally i wouldn't bother unless your prepared for sorting the engine out and a new gearbox, given the costs i wouldn't bother

Got a mate that did the same with my first Blob WRX 360/370 was the end result, he's run it like that for a few years, only problem is that you do have to be mindful of the gearbox limitations and as such he does tend to take it easy...

I've driven it and it does go well but it kind of lacks the sense of urgency of the 2.0L ... he was sat in the passenger seat $h!tting himself... and I was worried that I'd end up forking out for a new gearbox for him... so in the end... not much point or fun really when you're constantly waiting for something to break.

If the car is like £3k then ok worth a punt... but if they're asking much more than that... which I suspect they are... with that milage and engine combo I'd give it a miss.

Thank you for the very considered logical advice Ditchmyster through actual experience in this situation. The car is at the £4.5 K mark. I am going to take your advice & give this a miss. The straw that broke the camel’s back is what you say about always worrying about the gearbox when you are giving it the wind that shook the barley!!!! I would be buying the car for fun as I use my old girl of 16 years (v5 uk classic) as my daily runner so what is the point if you’re constantly worrying/waiting for the box to go bang!!!! :freak3:


Couple that with the sound logic & advice kindly provided by the other guys too then definitely not going to bother.


Thanks again All for the sound advice.


Cheers Paul :thumb:

speaking from personal experience, 350hp/380lbs torque would not easily see off an 05 5speed box unless you were doing lots of 1/4 mile sprints with launched starts.
Trev

As much as I love the 5 speed box I'd have to disagree... it's a gamble that some get away with, but... there are many that have lost that gamble over the years as has been very well documented on here and why the 6 speed exists, newer TY54 5 speeds are better than the classic TY52 boxes but they just can't handle that kind of torque when used in anger.

Personally I like to drive without having to worry when I stamp the loud pedal.

dont forget the VBAAA 5 speed box :).

im running this box at 390/390 on my super duper kinugawa turbo ! lol ! :D

but we're talking about the OP's power level on a standard clutch and a possible step up from that. Shouldn't be a problem on spirited road use, track/strip due to the car's mileage, probably yes.
My 5 speed gave out at 400hp/440lbs after being damaged by a breaking clutch at Santa Pod but for me the box was never the weak point.
Trev

well it broke didnt it?

Like I said previously "some get away with it"... there are always going to be exceptions to the rule... but it's widely accepted and proven on numerous occasions that the 5 speeds don't fare well with higher than around 350/350 and many have broken with a fair bit less.

As I said I love the 5 speeds, so I'm not coming from a haters perspective... but they do have their limitations and even at 350lbs I would still be mindful of those limitations and waiting for it all to go badly wrong one day.

And don't forget... the better clutch will just increase the strain... as a slipping clutch is effectively damping the torque.

hawk 5 speed is considerably stronger than all the other to be fair

I was in the same situation as you a few years ago, with the same setup, bug wrx with 2.5 bottom end but with 2ltr heads on a vf35 my 5 speed gave in for the 4th time 3 times with previous owner I discovered I went 6 speed, then rebuilt the engine put matching 2.5 avcs ported and polished heads on as it went into a hawk with dbw, upgraded various other parts and now have 500/500 plus.
All done by Scoobyspares and mapped by Andy Carr

Hi all,


Just had a look back & read all the updates. Great discussion & some good info.


Thanks to all for input, very much appreciated.


Cheers Paul:thumb: