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STI blocks vs non STI blocks, whats the difference?


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I have a '96 GC8D WRX STI and its run a bearing and destroyed a piston and rod.

I have priced another engine for it and the cheapest i can find one is 3k because its an STI.

The heads are still good, as are the turbos and everything else so all i need is a replacement block.

Obviously STI's have forged pistons and other wrxs dont, but is there any other difference like forged rods, forged crank or stronger block?

If i bought a legacy/wrx short block and put forged rods and pistons in it and used my heads etc would it be as good as a factory sti engine?

I have been offered a set of eagle rods and wiseco pistons for $900 and can buy a legacy turbo short block for about $300 which would make a far cheaper rebuild.

Anyone have an opinion about doing this?

Thanks.

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Being a 96 STI the pistons are a semi forged type, so theory would be that if you bought even a semi or open deck block and put forged rods and pistons using the stock crank (no need to upgrade) and bolted on your heads you would have a stronger engine than your OE one.

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Ok great, so if i get a 1991 legacy GT closed deck block and put my forged pistons/rods in it and all my sti heads/manifolds/turbos etc it should end up a pretty good engine right?

I like this idea as it will be half the cost of buying another sti engine :)

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Your heads will bolt up to a closed deck block no problem.

Your STI is a 96 so should be a version 3, put it thus way;

A good strong basic engine would be a closed deck with forged rods/pistons and V3 STI heads which are considered to have the most aggressive cam profiles.

All single turbo generation 1 Legacys will have closed decks from factory theres a couple of tell tale physicality's of a closed deck block, externally speaking.

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 BC5RA said:

Early BC5 RS and GT Legacys all had closed deck blocks, they varie but most JDM WRX engines were closed deck until 94 however V3 STI RA had closed deck and standard STI had open.

word.

from the information i have:

V2 WRX RA closed

V2 WRX STI RA closed

V3 WRX RA ???

V3 WRX STI RA closed

v2 is EJ20G and was 95/96 so depends.. angled intercooler is v2

v3 is EJ20K and has different pistons, they have a shorter skirt than the V2's

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 kamineko']

[quote name='BC5RA said:

Early BC5 RS and GT Legacys all had closed deck blocks, they varie but most JDM WRX engines were closed deck until 94 however V3 STI RA had closed deck and standard STI had open.

/quote]

word.

from the information i have:

V2 WRX RA closed

V2 WRX STI RA closed

V3 WRX RA ???

V3 WRX STI RA closed

v2 is EJ20G and was 95/96 so depends.. angled intercooler is v2

v3 is EJ20K and has different pistons, they have a shorter skirt than the V2's

V3 WRX STI RA closed

I ve seen some that are open on RA's

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so is it really a big deal having an open block if your not chasing big power?

for that matter, do forged rods and pistons even matter in a factory engine thats only putting out 200kw?

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It's a matter of debate, but in my opinion you don't need an open closed deck block until very high outputs.

As far as 200kw at the crank is concerned factory internals (for the application) will be fine.

is that what you meant? Yes that is what i meant, Thanks.

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 kamineko']

[quote name='Qwerty said:

V3 WRX STI RA closed

I ve seen some that are open on RA's

/quote]

yeah what years? ra, ra-sti or ra-ltd? i believe v4+ all open until the later semi-closed

Rickys 96 v3 Sti RA was definitely open - as it was opened up for its rebuild lol.

Some v3 type R's have closed but others not. Maybe they ran out at some stage in the factory !

You don't need a CDB but since they cost so little out of the total rebuild cost and give you piece of mind why not ?

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from what ive found (and im doing it my self now) you dont need to get a closed deck block unless you're building a full on race car...

get another STI block, bore it, hone it, then get pistons to sute, use factory rods and crank, im using forged JE postons and race bearings, if youve run a bearing you NEED to replace the oil cooler as there is no way of garenteeing you have all the shards of metal out of it. with a few other bits ane pieces its costing me around 8K.

all my info comes from Bruce Saxton, he use to build engines for Possum Bourne so personally i take this info on good authority, people will tell you different and thats their progitive (spelling).

MY2C

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Just a question in here, what constitutes a full on race car though ? Is that in relation to the amount of power you are trying to put out, or maybe the reliability you'd expect ? If it's power, what can a open deck go up to ( or does it not work like that ?? )

After having my car for a couple of months I'm looking at what the next stage for an engine transplant might be.

And, I've been looking at those 2.5l shortblocks. I'd expect that it would be a good idea to change out all the pistons, bearings (<--insert other engine related stuff that may need to be replaced that I have no idea what they're called )

i do have a 2.5l block thingie in the garage with no other bits, but I don't know anything more about it.

Have a v5 sti ra btw.

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 caspros said:

Just a question in here, what constitutes a full on race car though ? Is that in relation to the amount of power you are trying to put out, or maybe the reliability you'd expect ? If it's power, what can a open deck go up to ( or does it not work like that ?? )

After having my car for a couple of months I'm looking at what the next stage for an engine transplant might be.

And, I've been looking at those 2.5l shortblocks. I'd expect that it would be a good idea to change out all the pistons, bearings (<--insert other engine related stuff that may need to be replaced that I have no idea what they're called )

i do have a 2.5l block thingie in the garage with no other bits, but I don't know anything more about it.

Have a v5 sti ra btw.

I would say you wouldn't need a closed deck block until your pushing boost levels of over 24psi, or [email protected]

Basically closed decking stops the bores moving around at the top which prematurely wears head gaskets.

So if your building a motor to support big boost then start with a CD block, think of it in the same lines as uprating your fasteners and bearings for greater load.

From what I've seen good reliable power for EJ subaru race cars would be around [email protected]

Why would you want to upgrade? EJ207's are great engines.

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ok so what other things need to be upgraded in an ej20 when going for big power?

EJ20's have a bit of a bad reputation for running bearings...would using ACL race series bearings be enough to fix this or are there other issues?

I'm rebuilding my V3 STi engine with a closed deck block, eagle rods and wiseco pistons so it should be able to make pretty good power....what would be the next weak link of the engine that is likely to fail?

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