3 replies to this topic

[Tupers]

I'm sticking with the small bore engine for my estate but looking to do something different and do a big overbore + blow through supercharger, maybe efi. I've got an engine that's with a friend in Wales at the moment that's been fitted with 67.95MM Hillman Imp pistons pushing the engine to 1214CC but as of yet I don't know what condition they're in or if they're useable. I've been looking for other pistons and thought I'd stuck lucky with Mini Sport AU's +120tho 998 ones but it seems that the gudgeon pin on a 1098 piston is high than on a 998 and fitting 998 pistons would cause them to protrude from the block.

Now getting another set of Imp pistons (if I do need them) is going to be expensive so before I potentially go and spend a hard earned has any one else got an suggestions on what might work? A Yamaha YZ250 pistons is the same size but I have doubts about using a mega long skirt 2 stock piston on a high torque car engine.

[bmcecosse]

If you are supercharging the engine - you don't NEED to go big bore! Just use the next standard size up - the s/charger will make all the power you dare push through the weak 1098 crank anyway.

[ace01]

I am sure that Swiftune sell Omegas in 1098 plus various overbores. Expensive at around £460, but a really good piston.

[Wil_h]

If you are supercharging the engine - you don't NEED to go big bore! Just use the next standard size up - the s/charger will make all the power you dare push through the weak 1098 crank anyway.

You're missing the point on how 'charged engines make power. The don't increase the peak stress (td exhaust stroke) this is governed by rpm. What they do is create a faster hotter burn which increases torque mid stroke (a low stress point). So any inherant weakness in a 1098 crank will not show up if you stick to the general rule of thumb of 6k rpm limit.

As it goes though, what SC are you planning on using, the M45 is a bit crap, well all superchargers are a bit crap.