10 replies to this topic

[snowy653]

Hi ya folks, hope you are all well.

I am looking at rebuilding my 1275 engine and was wondering what the best pistons to use are? Am looking at rebore to +60 and was gonna use flat tops but have read a few forums that have said to use the 21253's as these are a better piston. Something about the compression ratio to high for todays fuel!!!!

Am gonna use the SW5 as by all accounts this is the dogs dangly bits, Have got a 3.1 diff in the box for a bit more top end. 

Dont want a track monster just something for every day use to have some fun in, if you know what i mean.

Many thanks in anticipation to your replays.

Berty.

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P21253 are a good all round piston, fine for every day use. Running flat tops is really for out and out performance, and to obtain a higher compression ratio. The std ratio of the P21253 is 9.75 which is plenty high enough for an everyday car.

[MrBounce]

I am building a 1293 and I have 21253s to go in - I took the advice of Cooperman on here and there's very little he doesn't know about Mini engines

 

As Simon says, a very good piston for a road engine.

[minilee94]

The piston shown I think is a hepolite piston I'm not sure I have looked but if it is as said before is a good piston they were used as standard I think well my engine one I stripped it down I found to have hepolite pistons and that was a standard 1275 spi

[MrBounce]

The 21253s are indeed from the same company (AE) but they're now called AE Nural rather than AE Hepolite

[minilee94]

Ohh right okay was a close guess

[ACDodd]

Ok the first thing you need to do is plan your build. You need to work out what piston and head combination will give the cr required to work with your cam. So what head chamber volume have you got?


Ac

[snowy653]

Have got the 12g940 head to fit, its standard at the mo but am thinking of fitting some rimflo valves in and getting the valves seats done.

[snowy653]

The head is the 12g940 standard at the minute but looking at some rimflo valves and new valve seats. Probably leave the rest as is.

[ACDodd]

Is it and unleaded factory head?

 

AC

[snowy653]

Not sure at the mo but workin on the assumption its leaded so have to get the valve seats changed I think. Something sbout the seats burning out or somet like that.