5 replies to this topic

[hmshood11]

Hi,

I am looking at rebuilding my 1275 engine and I thought that I while the engine was out I would upgrade/replace the pistons but I'm not too sure on what to look for. Can anyone please shed some light on the different types of pistons?

Thanks

[sirweste]

An unusual "upgrade" option this one.
Any reason why your thinking of new pistons?
ECU engines are a bit of a pain when it comes to pistons as you must try to keep the CR correct i.e. as close to standard as possible - unless your going down the programmable ECU route too

[hmshood11]

To be honest I'm in a unknown area for me with regards to pistons, I don't know a lot about them, I have made other mods to the engine an I have heard about people changing the pistons but I am unsure whether A. I need to or B. to what.
It is my plan that at somepoint I will go down the road of a programmable ECU but not yet.

[sirweste]

For advice on upgrades you'll need to post up what state the engine is currently in. Pistons that increase CR will have to be done at the same time as prorammable ecu

[Sprocket]

AE 21253 +0.50mm (+0.020") will be more than up to the job and will give a compression ratio close to what you have. You would have to build the engine up without rings first to measure how much to skim the block, if at all to get the compression ratio back to the standard 10:1 of a Cooper, if that is what you have or just flash off the top of the block to freshen it up fr a 9.5:1 for the non Cooper. then take the block back to the machine shop. You need to physicaly measure things to see what you have and decide where to go.

All after market pistons are designed in such a way to allow a skim of the block to freshen it up, and for ease of selecting a desired compression ratio.

Minispares do the Mega pistons which are a higher performance piston, then there is Omega which are a higher performance piston still. Then you have the Forged pistons. All of these are not needed on any of the injection engines. The extra cost of these pistons would be better spent else where

Injection engines will take a slight increase in compression ratio.

Edited by Sprocket, 24 January 2010 - 11:30 PM.

[sirweste]

My compression went up slightly since doing my engine. Doesnt run as happy now, though there were afew things that changed so I can't pin it on the compression for sure.