Hi guys, I've had a hunt around but can't seem to find much on it (probably just me i know) but if i was wanting to put a 2.5 bottom end in my Sti Type R is it possible to use the existing heads and ancillaries, inlet,turbo etc?
would it be a case of literally swapping the block for a 2.5 then remap?
Or is there far more to it?
I presume there is a lot more to it than just a straight swap so any info/links much appreciated!

many thanks

Si

 

you could just get your block bored out to a 2.5 .

 

Mmm, not quite mate...LOL,..... bit more to it than that...

Si, yes, in short you can of you wish simply bolt everything from the 2 litre onto the 2.5 block and get a remap and away you go..... but you can also go silly at the same time....

Ron...

 

It's not quite that simple mate, the crank is a different stroke for a start.

The 2.0 crank is 75mm while the 2.5 has a 79mm crank.

Pistons are different as well obviously, 2.0ltr pistons are 92.5mm while the 2.5's are 99.5.

I'm not sure that the 2.0 block will take a rebore of +7mm? I doubt it very much tbh although i stand to be corrected if anyone knows different

You would be better to start with an EJ257 block, don't use the EJ25 block as the main bearing journals are smaller than the EJ257, 48mm vs 52mm iirc and you will not be able to use the EJ257 crank which has the 52mm main bearings.

As an alternative to an EJ257 block, you could reliner the 2.0 block with thicker, stronger and bigger liners - better for longer life according to some (me included as i have done this to try to build a rock solid 2.5 last forever forged build! over engineering is not a dirty phrase )

Everything else will bolt on, some modify the heads so that the combustion chambers match the larger bore better but this is not essential as many just fit and forget.
You will need a remap to cope with the extra capacity, by going to 2.5 you are increasing by 25% so you need to manage that extra flow as it were

 

yes everything swaps no probs.

just done an ej257 conv on my 97 wrx. everything bolts on. just make sure you have a pretty good clutch as more torque will shread it.

existing parts will restrict it but put good internals in and your laughing cause you will have a solid bottom end. everything else after that is easy eg turbo injectors etc etc they can come once the bank balance recovers.

only thing is the comp ratios with 2 litre heads. i put in 1.6mm metal 3 layer cometic head gaskets to compensate it.

just running it in just now and all seems well. getting ecu and set up 10th dec and can't wait

 

oh yeah and no you can't re bore 2litre to 2.5

 

dazdavies has done it with one i think, i could be wromg though.

 

Thanks for all the replies guys, by the looks of things i should be alright to just use existing parts with the new block which is excellent news!



So your running around in it without it being remapped?

 

you can run it in yes, just stay off boost until mapped

 

As an alternative to an EJ257 block, you could reliner the 2.0 block with thicker, stronger and bigger liners

 

ok its official im thick lol , i pretty sure you can rebore the closed deck block to a2.5 and obviousley change the crank etc etc ?

 

I wouldn't say thick mate, not as well informed about the complexity of Subaru engine building maybe

The CDB will have the same size liner thickness as a semi cdb and open deck, Daz D used a CDB and relinered iirc, there will just not be enough "spare metal" to remove through the full length of the liner to bore out another 7mm

 

nope, he's being thick.
the 2.0 cdb can be relinered to 2.33 or 2.5 or whatever displacement you choose.
There are 2.6L and even 2.8L options although that seems a step too far.

 

missed smiliesa from my above post sorry

 

well there is no way im letting a mapper loose with a 4 grand engine until i put some miles on it. so yes you can drive it off boost which is very boring but these things have to be done i suppose.