Thanks for the explanation of dowels: I saw them on the pic, but never twigged that they weren't there on mine.

Should I have had that done? Mine runs 400/400.

 

No need at that level.

 

Thanks, that was what I wanted to hear.

 

Any comments about this solution for a 2.5 block?

http://www.outfrontmotorsports.com/engine_blocks.htm

 

solution looks good but I'd imagine its cost prohibitive...particularly when compared to the dowel option

 

I was advised when having my 2.5 built that it's best to just stick to the mid-late 400s and leave it at that. At this level you get a very, very capable road car.

If you want assured reliability with 500bhp + then the 2.5 doesn't seem to be the optimal solution.

Ns04

 

"Assured reliability" is not always an option for the 2.5 even at mid 400's! Headgaskets are the real concern at this type of level, and more likely than not they will let go at some point.

Depends on what you understand by the term "reliability" as it can all be relative.

 

If it don't break on me..... it's reliable!!

Crucially though, I'm kind to my cars; they are used, not abused and VERY well cared for.....a track

Seriously though: I believe in doing in right first time, so mine got the lot thrown at it, up to and including stuff that I'd probably get away without as I use the car exclusively on the road (e.g. oil cooler and baffled sump, parallel fuel lines, inlet manifold spacers) and when David said: call it quits there for the sake of the block... I said: "Yes sir!"

Beefier studs and headgaskets should be part of any 2.5 build at that level shouldn't they? My understanding is the frequency with which head gaskets go at that level is overstated. The big weakness in the 2.5s is the std pistons, and I don't know of anyone who has tried to get anymore than 400 out of them!

 

What head studs have you got then?

 

OP.
If you build a 2.5 scdb a "must have " is a cooler thermostat. Newage 2.5 motors run quite hot to pass eu emissions & this can't be a good thing on a tuned motor.

Dave

 

"must have" .... are you sure!

 

if replacing something that costs about £70 helps protect head gaskets , heat issues, personally i would say it would be a must have.

 

I managed 450 bhp on a standard 2.5 short motor a few years back, 8,000 miles without issue before I sold it on.


Why is it a "must have" over a standard one? I can think of more essential items which are must haves

 

Spanner Monkey,
I must of been "silly" then, as I ran with the OE thermostate on my Cosworth 2.5 with 500+bhp and cained the **** out of it for 16+k miles and never had a problem with water or oil temps.

Daz,
Why did you put that about your old motor.... this will now become a matter of fact and everyone will be stating the new limit has moved to 450bhp on an OE bottom end. Shame on you for starting the next ScoobyNet Myth!

 

LOL at Scoobynet myths.

 

Like the majority of us on here most of our knowledge comes from other people, what we've picked up / heard over the years. The company building my engine highly recommended a cooler thermostat due to potential heat problems with the 2.5 motor. When spending £????? on a build an extra £70 for a thermostat is in my mind a must have.

Ohh 450 on a std bottom end, could have saved myself a fortune

Dave

 

Dave,
I don't dispute how we gain our knowledge, but I trust you understand that when one person states a "must have" on these forums, before you know it..... it becomes gospel and everyone starts quoting it. Unfortunately that is simply not the case with regard to changing the OE thermostat. You clearly state above your engine builder "recommended" it and that is a whole world of difference to it being a "must have".

 

Shaun
I see your point, not my best choice of words, just the way i see it for added protection.
Although i believe a cooler thermostat is highly recommended on a 2.5 motor


Dave

 

lol

 

Is the coolant flow different through a EJ257 block?

 

Shaun, you're right. I only recommend pushing a standard EJ257 bottom end to 400. Mine was 450 as I picked the short motor up for £500 and deamed it dispensible. It never let go.

The coolant system is exactly the same just that th water jackets are smaller due to the bigger bore size. Standard thermostat is perfectly adequate for the job. it's good to have a cooler opening one but it certainly isn't a must have.

 

It's rare you get experts to agree on "necessary vs nice" mods to the car.

Good example, when I had my 2.5 build done, two ultra respected (and I do mean "ultra respected") subaruy tuners disagreed about whether an oil cooler was necessary for a non track car. I err'd on the side of caution and got one.

There is always more than one way to crack a nut......or a block! lol

Worth reflecting on the fact that not so long ago, 300bhp was regarded as "pushing it" on these cars lol.

Personally, I recokon there is no point having something unless you can use it properly and not spend 90% of your time watching guages or s*itting yourself that something is going to go pop. So, althogh I know that some people have run 2.5s above 400bhp there was no way I was going to do it.

It's getting a fit/forget/enjoy solution that costs!

Ns04