Ok, as everyone seems to do the "what power can i expect" even though its a bit of a mystery until its done anyway......what do you think to this spec?

2.5 short block w/cp pistons and eagle rods
UK WRX heads
Ported Headers
MD195 Turbo
Hybrid Frontmount IC
3.5" APS Turbo back exhaust
650cc Injectors

 

Not sure about the heads/cams.
Most use Sti V3 onwards for the cams and a better design.
These are comments purely on what I've read recently.

You really need to 'talk' to John Banks.

Graham.

 

i know the heads are one of the limiting factors along with the turbo, this car isnt going to make huge power compared with most. (by huge i mean 400+)

 

Depends on rollers, I'll take a guess at 340 BHP +-10%.

If you had a strong turbo, strong gearbox and could keep the headgasket seal it would be nice to run lots of boost low down to get peak power across a huge band Few ifs there though...

 

too true, i think what i was going for was strength in the block over out and out performance this time round. The turbo can always be swapped for something larger that will make the 2.5 work a bit.

 

i just hope its not the -10% of that figure john

 

I do not think there is much of a loss with UK heads , when either a smallish turbo or a standard block is used. you are also running ported headers which will also bring things down lower and save you revving the engine higher than it needs to.

since you have decent internals in the block and may consider a larger turbo at a later date , imo it makes sense to try and get some sti heads just now.

 

i just dont think that ive got the budget for it right now, and also if this turbo isnt really going to stress the UK heads i have then surely changing them could wait until a larger turbo was on the cards anyway?

that is the ultimate plan though, just swap the turbo at some point for something larger, i still have the nitrous system for any "fun" moments when i need a little extra grunt.

 

Might be worth pointing the coolant overflow at the windscreen whilst setting up the nitrous to see when/if the heads lift.

 

im confused ?? what do you mean john?

 

If the cylinder pressures go very high with the nitrous the pressure may help to separate the head from the block slightly, which will allow some combustion pressure from the cylinder into the water system. When this happens, the radiator cap's rating will be overcome and a jet of water will go into the overflow tank. If you instead point this hose at the windscreen rather than the overflow tank, you'll know if you are overdoing it whilst setting up. Once a headgasket starts to leak it degrades, so spotting it early may save you a lot of hassle.

A small shot should probably be OK, but consider that even a 50 BHP shot at 2600 RPM will add just over 100 lbft, and you could very easily have 450 lbft, which on my engine was too much for the headgaskets.

 

ahh thanks john i see what you mean. Thats a very good way of telling too

Ill be sure to use that method when setting up the system. Although id never use it before 3000rpm......as that seems to be the normal level to switch it on at.