scoobchrissy

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How cheap could i get a 2.5 short motor for and would 2002 WRX heads go straight on with 2.5 gaskets any info appreciated thanks

chrissy

scoobchrissy

iTrader: (1)

pat

EJ257 short motor is relatively cheap, and it will fit with the WRX heads, but it's not a combination that I would recommend, most people that I know who have gone down that road have been disappointed. There are other better ways of building a 2.5 litre engine.

Cheers,

Pat.

TopBanana

What would you recommend Pat? Head-wise, specifically.

scoobchrissy

iTrader: (1)

Cheers for the reply Pat i know it's not a good combination but i was trying to do it as cheap as possible i've just spent a fair amount on my engine to correct one thing and now there's another prob, plus i was thinking of upgrading it at a later stage (after hols) so when you say cheap how cheap thanks again..

chrissy

pat

TB,

For simplicity and future parts availability I would recommend large port Phase II heads and cams with a profile designed to drop the dynamic compression ratio in the area of peak volumetric efficiency so that you get the benefit of high mechanical compression where you need it without incurring the penalty of poor thermal efficiency resulting from excessively high dynamic compression. It will also help the longevity of the valves if the system as a whole was designed to work together, rather than just a cobbled together assortment of standard parts. Some combinations of standard parts work well, most do not. Do not be fooled into thinking that you can improve the situation by fitting thicker head gaskets to lower the mechanical compression ratio, if it isn't right, it isn't right, and no amount of band aids will make it right; only the proper selection of components designed for the purpose at the outset will stand a chance of working well.

Don't dwell too much on the mechanical compression ratio, it is purely incidental if everything else is correctly specced..... but therein lies the challege

Cheers,

Pat.

pat

Scoobychrissy,

I haven't had occasion to buy an EJ257 lately so am not sure of current pricing, but others seem to be suggesting something in the UKP 1200 ball park.

I appreciate your dilemma, but I would suggest that you'de be throwing good money after bad if you were to simply swap the short motor, you'de get far better results and enjoyment from the car if you take your time about it and do it right.

As I understand it, your existing engine problem is not acute, and you have the opportunity to take the time to choose the right parts for the job. Unless the existing problem is more severe than I think it is, it should be quick and easy to fix, so I would recommend doing that and then thinking about future plans separately from existing issues. There's no point in doing half a job now when you can get it sorted now and do it right in few months.

Cheers,

Pat.

scoobchrissy

iTrader: (1)

Thanks for that Pat and like you said i'm in no immediate rush so i'll start by sorceing the right parts that i will need and when the engine does go bang at least i'll be there or nearly

cheers chrissy

Pavlo

Sorry pat, but that is an oxymoron.

Paul

pat

Paul,

you can't categorically state that it's an oxymoron, because I didn't state specifically what the drop was and what it was referenced against. The only sensible comparison in the context above would be to compare the new profile to the standard profile, and it is entirely possible that a more effective profile would yield a lower DCR at the point of maximum VE of the original profile. It is also entirely possible that the new profile never achieves the same DCR, and taking this one step further, it is also possible that the new profile will have a lower DCR at its maximum VE than the original did at the same point.

I will happily agree that for a single cam profile in isolation, DCR and VE are linked and that the highest DCR will occur at the VE peak, therefore the DCR cannot be lower at the max VE point than anywhere else.

Cheers,

Pat.

DuncanG

Interesting stuff.
So do these cams exist or who can design them?

pat

Duncan,

from my comment "Some combinations of standard parts work well" you can infer that there are some standard Subaru camshafts that do work quite well, and I'm sure that as time progresses there will be more after market profiles which are specifically targeted at the requirements of the 2.5 litre motor I would suggest that if you don't want to get too involved in the theory etc, then just use a set of STi5 / P1 heads, the profile seems to work somewhat better than the UK profile.

Cheers,

Pat.

scoobchrissy

iTrader: (1)

So STI5 or P1 head's is what i need then Cheers Pat and of course a short motor

scooby-si

want about 2.33ltr and v3 heads and cams??

scoobchrissy

iTrader: (1)