Looking at upgrading a couple of engine parts seeing as the engine going to sitting on my tool bench at the end of the week. So after driving with the 2.5 litre for the last 6 months I've enjoyed the extra torque but I've been missing the high revs of the original 2.0 litre. So I've decided to stick with the open deck 2.5l STi block but fit some Crower 4340 extreme billet rods with ACL race series bearings and ARP rod bolts. Weisco 99.5mm racing forged pistons and keeping the original EJ257 crankshaft. All in the hope of increasing strength with the ultimate goal of making the car good for 7000 rpm. But my main problem is with deciding what cylinder heads to use. Originally I was considering using STi V3 heads with under bucket shims as they were fitted with higher profile cams than the V2 and V4 and where supposedly a stronger cast. But all V3 heads I've managed to find have a common crack problem around the spark plug threads and as I'm looking towards raising the boost pressure to 1.6 bar I'm a little worried of the cylinder heads cracking. So contemplating purchasing Cosworth cylinder heads from powerstation as I'm sure the flow rates and cam profiles would allow for the increased power band I'm after. Does anyone else have any other suggestions with regards to what other alternatives with regards to what cylinder heads and camshafts I could use. As 2.5 k for Cosworth heads seems alot but secondhand STi V3 are fetching up to 700 pounds and would most likely require new valves and retainers and reflowing. I'm looking at carring out the engine rebulid myself over the next 3 months so any suggestions with regards what parts to use would be much appreciated.

 

Another question, Does anyone have first had experience of using DH22 Kent cams and what the extra 268deg total duration with 9.65mm lift amounts to in maximum rpm output?. Sti4 cams have less than 9mm lift and total duration 256deg. I'm under impression Sti3 cams have a little over 9mm of lift from memory and would really like to know the difference in the sense of maximum rpm output?. I know the sti3/4 platforms are the same and are supposedly stronger than the earlier models so looking into a Sti3/4 head with kent DH22 cams all reported and flowed to suit my 2.5l block. Or even better does anyone have a set of kent cams fitted which I would be able to experience?.

 

IIRC you can buy complete JDM heads from Gruppe S, haven't got time to check as I'm in work right now.

I know you've said your sticking with the OE crank but why not consider an uprated steel billet item from RCM??

It's much lighter and stronger and it would be easier to achieve those revs your craving

Whatever you decide, good luck with the project and keep us informed.

 

I believe the Cosworth heads from Powerstation and the heads from Gruppe-s are for Newage cars so have AVCS, not sure if this would work with your ECU/wiring loom.

 

Thanks Dean, I completly over the fact these are indeed AVCS. I'm now looking towards going down the route of reworking my original heads depending on condition. RCM do a cylinder head port and polish and I'm going to speak to olly and RCM with regards to cams.

 

I've read that opening the chambers up to suit the bore of the 2.5's make the head gasket failures less likely.

 

I got lost in the detail half way through the first post

Let me throw a suggestion in and say what about a new age jap spec engine transplant ? e.g. sammy was selling his spec c engine not long back maybe Litcho could source one from another T25 conversion ?
Mind you how big's the cheque book would be the next comment.

 

Maybe even worth dropping Ron at Axis Racing an email and seeing what he could for you. Sourcing a built engine from him can work out cheaper than cracking your existing block open.

 

Axis Racing stage 6 capable of handling 600 bhp for 3000 pounds!. Wow thats some motor and a 2.65L, I can only dream of the torque this puppy must throw out . Match this up to a stage 2 valve train capable of 9500 rpm and this would be a car even I'd even be scared to enter. How much do you think delivery plus duty would be?.

 

These are worth a look aswell, Gruppe-s race spec engines:
Subaru Built Motors / Race Engines

Stage 1 is pretty much what your planning on building at $2800 (about £1450), Bargin.

 

Thanks Dean, I've now entered a whole new world, full sleeved liners seems to be the way forward. I've sent a e-mail the Axsis questioning the reliablity with regards to liner flexing at 2 bar boost pressure. I've also questioned choice of crankshaft with regards to inertia weight over lighter speced crankshafts and how this effects the balance of rotation. Awaiting response so I'll keep you all posted once received.

 

blimey, thats some good prices, I know what I'm going to do when the old girl's engine bites the dust

 

And me , Gruppe-s stage 1 for sure. Price's are very good at the mo due to the high exchange rate. Wonder what the shipping and tax would work out as???

 

Interesting thread. So which is the best/strongest standard cylinder heads for modifying with?

And dont forget the VAT on the cosworth heads ( which will take it to 3k )

 

I think delivery is stated on the Axis Racing site. I know that if you ask Ron nicely he'll change the description of the contents so that the import duty isn't as heavy as it could be

 

On engines not requiring cylinder heads with valve trains which are variable valve timing compatable. The STi V3/4 heads are supposedly made with stronger platforms and are less prone to cracking. But all the cylinder heads in which I've enquired about have cracking around the spark plug gaps. So it's a matter of a waiting for the right set to come along. As for power I've been told standard STi V3/4 heads are good for 450 bhp, for engines with increased displacement some further head work is required to increase flow rates. STi V3 heads are the most sort after due to the cams having slightly more lift than V4's, all in which I've yet to find evidence to support this claim.

 

Ron at Axis Racing has emailed me back with regards to reliablity with the sleeves used in the stage 5 & 6 blocks. He has yet to have one fail and has customers running 2.6 bar . This is more than Simon Norris who is running 927 bhp at 2.2 bar

 

Think its time to call it a day, my car is slowly droping down the ladder, and to put it back where it should be is stupid money, a change of car post xmas is calling me thinks, good luck to all those with there plans/mods in 2007.
Subaru 3dr hatch, BFG shod, post Mexico WRC, now theres a thought.!!!!

John

 

have a chat with simb, He might want to take the gear box off your hands???

 

John Take yourself outside and give yourself a good slap!!!!

What are you up to !!!!!!!!

 

Decided to go ahead with the rebuild instead of buying another engine as only looking towards running the engine at 440 bhp max. So purchased my first goodies and awaiting delivery on Wiseco pistons, Eagle rods, ARP stud bolts and Tufnol Carp insulting inlet manifold gaskets. So that covers all my crimbo presents just need to buy all my families now.

 

Slowly shifting my way thru the long list of upgrades for my car, the engine is currently under assembly with the STi v3 cylinders being rebored to to suit the 2.5 L block. By only using a dremel and digital calipers, the over all bore width is accurate to Subaru specs. Next step is to use a metal polisher to reduce surface friction and to start on the other head and reground every valve.

The bottom cylinder head showing increase inlet side diameter.
Also whilst the engine is removed I've decided to remove unnecessary engine parts such a mechanical boost soleniod to further reduce weight and tidy the engine bay. Also primering the entire engine bay and repainting pure white and along with rocker covers and strut brace top mounts


Also my spec C 6 speed gearbox arrived today along with automatic proshaft and rear diff. Also fitting Brembo rear brakes onto newage STi hubs so no need to purchase a conversion kit. With a 2 week hoilday in three weeks time I should be ready for fitting the rebuilt engine and gearbox into it's newly painted engine ready for Andy forrest to work his magic.

 

looking good, If you don't mind me asking how much for the box?? and where from??

 

I bought the box from Glenburgie Cars (breaker in Scotland). It's only covered
22,000 miles and with the additional parts I'd paid 1055 pounds delivered. With drive shalfs you will be looking at paying between 1200 - 1400 pounds depending on age miles etc. Many places still ask 2000 pounds which is complete rip off when considering the amount of Subaru parts available on the market.

 

Nice one Jon. Now your engines out of the way i shall be around next weekend to pinch your speedo cable to see if that fixes my problem. Also my arms are still aching from manhandling your engine . When r u planning to put it back in so i can arrange to be unavailable lol. Anyway while yours is out of action i though we could use mine as a donor car for some of your mods,Don't want those brakes seizing

James

 

No worries Bev, I'm removing the mechanical speed sender from original box to replace the electrical sender in the 6 speed today. So I'll remove the speedo cable ready to test on your gearbox, maybe worth while running both clocksets off your gearbox as to find route cause. I know of a place where we will be able find a cable and sender if necessary.

 

Damm thats not bad at all, fitting a new clutch and flywheel at the end of the month, may be worth chucking a 6 speed box in at the same time .

 

Just phoned Glenburgie for a quote for a UK spec STi box with just the prop shaft and linkage, but they haven't got any in stock anyway.