Alternative Pistons For A 1098 Overbore
Turbo Mini Forums

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.

Change the block? Or liner it?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

i thought the only difference in the block between 998 & 1098 was the crank?

It is. Rods and crank are different.

If something is worth doing, it's worth doing half of.

and pistons obviously

If something is worth doing, it's worth doing half of.

You are correct, all a-series engines use the same length rods with different pin heights to compensate for the change in stroke. The only the 970 used different length rods

It sems you have two choices:

1) renew the pistons with the imp ones.
2) use the 998 pistons, but you'll need to use a 998 crank (block and rods are the same).

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

www.twin-turbo.co.uk

Ah appears one is wrong. I thought the 1100's used different rods. Live & Learn

If something is worth doing, it's worth doing half of.

I think that to use the imp pistons the block has to be decked a fair bit even on an 1100 so you may be stuck with them...

but they are available if you know where to look

http://www.hillmanimpspecialists.com/pricelist2.htm

http://www.swiftune.com/Product/459/omega-...a-flat-top.aspx

Thanks Joe C, I knew about Reg Patten anyway as my mate who's restoring an Imp put me onto them. I was more looking to see if anyone knew of any other models of pistons that where around the same size as the Imp ones.


I believe you can go up to +40 on an Imp piston before going through oil ways becomes an issue so I guess I'll start stock and leave myself some room for an over bore.