7 replies to this topic

[who_loves_the_mini?]

Im rebuilding a 1275 at the moment and will be reboring it to 1293, I am going to be ordering a 7 port head in the summer and will also be looking into turbo's at a later date, my question is are there any pistons I can use which would enable me to run the engine standard at the mo, then with the 7 port and then maybe with the turbo? I dont really want to buy new pistons every time I upgrade

thanks

[TimS]

You could use a faily low compression piston, but that would'nt be very efficient or goive very much power without the turbo. The other posibility is to find a piston that the crown could be machined down on, for when you upgrade to a turbo.

You can get way with running a turbo with a higher compression but you will be limited to low bost.

The head will also need to be modified again to get the best out of the 7 port.

[who_loves_the_mini?]

I would only be running around 7psi of boost, nothing crazy. Im going to get the bare head so i can get the valves custom done rather than being done by minisport

[Sprocket]

Asking a bit much from a piston, but then it all depends how you want the car to run Normaly aspirated and how much boost you wish to run, it also then depends on the size of the combution chambers in the head.

I would aim for a set of pistons for Normaly Aspirated and combustion chamber to give a compression ratio of around 10:1 on normal unleaded

Then when you go turbo, fit the best pistons you can buy with as big a dish as you can get so as not to be enlarging the combustion chamber in the head (all depends on how much boost you run). I personaly would leave the chanbers almost the standard 21.4cc so it can be run Normaly aspirated, relying on the piston dish to get the CR down. JE pistons do som whapping 18cc dish pistons and are tough as nails, but you will pay for them

Building one engine that will happily run NA or turbo and give good results is going to be some what of a comprimise in every way.

[who_loves_the_mini?]

so id be better sorting the NA engine out first and then looking into it more when or if I turbo and changing pistons over when I rebuild

[Sprocket]

You got it

[Tarks]

Omega forged pistons can be ordered blanks high comp FLAT topped
so your innitial dish could be set about 5-6 cc as the piston has the option you can then redish to more like from 12cc to 21.4cc later to suit the tubbie you choose and boost you intend on running ! oh you'll always up it bare that in mind !!!


if anyone is in doutb call MED or MSPD they will back up my info .
hope this helps !


EDIT: id go offset on dish too;) this will help when you need to increase dish is it could then be recentered when enlarging dish to correct cc you require ! again MED or MSPD will work out your dish required when you tell them the demand you require from your engine.

Tarks.

[Guess-Works.com]

personally I'd build the engine using 21251's which will only cost 80 odd quid and will good enough. and then when you come to do the 7 port/turbo conversion get some decent pistons designed for the application.

And if you're lucky enough to actually get the old pistons off the rods without deforming them, then you can sell them on.. and if you don't you aint lost much.