Currently have a brand new V9 sti block, crank, rods, CP Forged pistons, acl bearings, 11mm arp studs and reconditioned newage wrx heads in my 1999 Type R. Alcatek+toucan+newage coilpack conversion are already on the car but I understand i'll need the ecu update which can be a pain to get done.

The engine had done 1000 miles run in and 2000 @ 414bhp in a bugeye wrx when I purchased it. Made the necessary changes to run in my 1999 and its been making similar power for the last 2000 miles BUT the engine was originally built in 2008.

I always said that if the engine came back out I would have the block pinned or closed deck inserts (I never plan to run over 500 on it so may go with pinning) and would add avcs + decent headers to improve torque, driveability and response.

Question is, 2.5 AVCS heads, what sort of price should I be paying and are they a must or can 2.0 be used on my Type R? Have a sneeky suspicion my headgaskets are toast after she ran low on coolant the other day (pierced rad, temperature went to a max of 108C) and I'm thinking of having the engine out so I'm going to start getting things together. I do have a set of 2.0 avcs heads here, but 1 camshaft is cracked and 2 of the 4 plug holes have the usual common cracks.

The engine has always smoked a little, especially on cold start which I put down to the CP pistons BUT I wouldnt rule out valve seals. Last compression test showed 160-165 psi on all cylinders cold so I'm going to compression test again tomorrow. I have all the build sheets for the engine/spec etc when it was purchased new, but the details on the heads are minimal.

I'm running millers cfs 10w50 and dont feel that this is too thick but i'd be interested to hear alternatives.

 

;tbh i think you may be over thinking the situation mate- what has the oil usage been like? a little smoke on start up is not unusual,is the car smoking on boost or on the overrun?
if the engine is fairly well built 415 brake and 4-5000 miles should,nt stress even a 2.5 overly...
the head gaskets could be a problem if you went a long way with no water but they usually run like a bag of spanners with sludgy oil and water and pressurising of the water system when there gone

 

Oil usage has never been great on it, probably a litre per 1500 miles. It smokes a bit when you rev it but doesnt chuck anything out when driving. The turbo was new 1000 miles ago so I believe the smoke/oil use is engine related.

I know I'm not overly stressing the engine currently, I just know theres more potential in it and room for improvement, the avcs being 1 of them.

As you say, maybe I should just stop spending and enjoy it as it is and re-evaluate next year once the cars had long term use.

I'll do a compression test tomorrow and go from there

 

Bigger head studs would help as you will get a better clamping force on the heads as they tend to lift on the 2.5 running good boost causing the gasket problems ,,, I wouldn't build a 2.5 without using 14mm head studs

Can't use 2.5 heads on a 2.0 , only works the other way around

 

regarding the HG, just watch out for any undue movement of coolant into the expansion bottle i.e. the level creeps up from where it normally is after driving on boost. The issue with the radiator may or may not be significant, I had similar, didn't pay enough attention and ended up with a totally wrecked engine due to HG failure.
The WRX heads benefit quite a bit from porting work to match up each side and improve gas flow. Paul Finch worked on mine, so that's an option.
My 2.5 is sleeved and pinned, 11mm headstuds, cosworth HG. It's fine at 1.6 bar but it would be nuts to run much more boost.
Trev