Piston and compression ratio
Turbo Mini Forums

Hi all I am a total newbie and I am glad I have now joined the forum..
My question I am going to build over the winter a turbo engine ..
I have bought an A Series block pretty old( Fitted to early gearbox) its bog standard 1275 this is going to be for road use, and to be used for a run around for the Sumer weekends only.. 2.4 family so no boy racer.. I built a turbo mini 20 years ago and the one thing I wished I done then was to modify the engine as it used to detonate like al Qaeda so I would like to do my best to not repeat that.
Right so I have bought a good morspeed booster head, 27cc chambers larger valves and ported, I was thinking 18cc dished pistons and 1293 bore size.
Will the compression ratio be too low and therefor be hard to start and run rough. I am taken back that it's going to cost me £500 for four pistons (Omega) I'm not putting this on a track do I have any cheaper options, could anyone suggest a suitable cam and any subtle mods that I will need to think about during the build.. Well that's war and peace and info would be appreciated..

compression ratio wise 8.5:1 is a good target, maybe a bit higher, then you'll be ok upto about a bar boost assuming a good intercooler ect

as you have the 27 cc head already your looking for pisons with about 10cc dishes.


cam wise, std works ok, mg metro is better, Kent 266 better still, avonbar phase 2 is generally regarded as the best for all out engines.

Edited by Joe C on 19th Sep, 2012.