Thicker Head Gasket / cracked block??? :(
 

Managed to over-heat my '96 WRX STi version 3 import. (well played I know.. only trouble with those things unless you spot it immediately temp appears normal - course heaters don't work but unless you happen to be using them... grrr..) anyway..

It's non-standard (are any of them?? :D) running around 375 bhp on 1.4 bar VF35


Problem: had to skim the heads (8 thou / 0.21mm) they were fractionally out of shape.. pressure tested fine, excellent finish (surface ground) BUT keeps pushing water back out of the expansion tank. (starts under load then just continues..)

Anyone ever skimmed heads before? (I'm not 100% sure whether someone hasn't put a 22B (if they're any different?) power unit in there.. reason I say that is because bent a valve once, 22B valve, VF23 turbo on it originally (fitted to 1996/97 22B's) and snapped a gear linkage in gearbox and it matched a 22B close ratio box..

So.. does anyone know of skimming heads causing over-heating problems on STi version 3's? well, I suppose more accurately over-compression ratio problems? Anyone had similar problem? Does anyone know if thicker head gaskets would solve and where to buy them? (did cross my mind cracked block but I don't like to think about that to much lol)

And is the 22B different (I have seen adverts for 'decompression plates' for 22B heads (but even the suppliers don't know the reasons they're used!) There weren't any on my engine when it was stripped down..!

Any help would be HUGELY appreciated it's becoming a black hole for money!

Leigh

Leigh,
If you have a 22B engine,its marked on the block and would be a bit of a rarity :

http://img.photobucket.com/albums/v4...k24/EJ22-1.jpg

The max you can skim off a head is 0.012" ASSUMING it hasn't been skimmed before - the standard head height is 127.50mm.
Any more than this and you will start to run into Compression Ratio problems and getting the Inlet Manifold bolt holes to line up with the heads.
If the heads have been Hot Tank Pressure Tested, then IMO the problem points to head gasket failure/liner moving under boost/porous or cracked liner.
I have seen a 22B engine with "de-compression" plates fitted but that was due to the poor fuel available in the States when the engine was built.

Mick

Mick ...the Subaru encyclopedia strikes again :notworthy:

I had the heads skimmed on my STI V2,comitec gaskets and wossner forged pistons,no problems.sounds like your head gaskets have gone?

Stop Stalking Me :D :D

But seriously - if the cooling system is being pressurised that much, a Compression Test and Cylinder Leak Down Test would narrow the fault down.

Mick