20 replies to this topic

[lyesryan]

I am currently having an engine built and have now decided to have it converted into a 1380cc instead of a 1320cc, it has now come to the time where I need to choose the pistons that I want so what pistons would be best for this build I am  looking at spending up to £350 for a set  of pistons so what would be the best choice within my budget.

 

Thanks Ryan

[fwdracer]

Up to 7K rpm in a road engine? Omega.

[lyesryan]

what omega pistons how much dish ?

[Guess-Works.com]

dish size will all depend upon the compression ratio you want to run...

Your budget will only stretch to cast Omega pistons, an alternative is the minispares powermax pistons slightly cheaper than the omega cast

[mossy2a]

I agree, I would say the powermax pistons.

[Cooperman]

Slightly off topic, but why would you want to go to 1380, which involves more expensive pistons and much more expensive 'offset' boring for no real gain? The difference in power and torque is really minimal between those 2 sizes.

It leaves a block which it would be difficult to re-life and if looking for absolute ultimate power the wear rate will be high.

1320 is not a standard size, the standard sizes being 1310 cc then 1330 cc.

Why not just go to 1330 cc, that is +0.060" and use 21253-60 pistons which are a good quality piston capable of 7000 rpm and which have an 8.4 cc dish.

[lyesryan]

oh right ok I just want a good quality piston that will offer higher performance values.

[Cooperman]

The key to a good engine is in the build quality. I would recommend P21253-60 pistons giving 1330 cc, with a Kent 266 cam, a head with 35.6 mm inlet valves, all well gas-flowed and with a compression ratio of around 10.2:1 for road use. The induction system needs an HIF44 carb or twin HS4's and the exhaust needs to be a 1.75" diameter system with either an LCB manifold or the later Cooper ex. manifold.

Properly set up with a matched distributor you could expect between 78 and 85 bhp, maybe slightly more, but the most important thing will be the really good mid-range torque. Peak power will be at about 5700 rpm and peak torque at c.4000 rpm.

[jaydee]

On this forum omega are quite popular

I'd say much better if you talk in person to a few proper engine builders and get your conclusion.

[Guess-Works.com]

On this forum omega are quite popular

I'd say much better if you talk in person to a few proper engine builders and get your conclusion.

 

I'm not sure what you are trying to infer ?

[Cooperman]

Before advising in detail it is necessary to know for what the car will be used. Is it for racing, hill-climbing, sprints, rallies or is it just a road car? Is it governed by any series regulations (e.g. Endurance rallying, Miglia Racing, etc)?

That will determine the optimum engine specification and from that the best pistons for the application.

Is engine life an issue or will it be re-built every year?

[jaydee]

 

On this forum omega are quite popular

I'd say much better if you talk in person to a few proper engine builders and get your conclusion.

 

I'm not sure what you are trying to infer ?

 

 

I'm not trying to infer, exactly the opposite

I'm saying that its better if he has a chat about his engine build and budget rather than the forum, if you browse through TMF looks like theres only omega for everything performance, which you know its not true

[Cooperman]

A really good piston is the Karl Schmidt, if you can find a set. I paid £500 for the last set I used, but they are very strong and durable.

I used a set of 21253 for an Endurance Rally Car as the regulations requires standard pistons and the 21253 is listed as the replacement piston for the 1990 Cooper 1275.

Everything was balanced, it had an MG Metro cam with the head lightly cleaned up (it was not allowed to be modified). The car was competitive in its class and it revved to 7000 rpm with no piston issues.

I happily use the 21253 for up to 7000 rpm and 10.5:1 CR figures. Over that a more specialised piston is needed, like and Omega or a Karl Schmidt.

For a road car it is really never necessary to go to more than a 21253.

[lyesryan]

Hi I understand what you are saying about the built quality which is why I am getting a professional engine builder to build the engine, he used to build both race and rally spec minis back in the 1980-90's. the reason for me choosing the 1380 is that he has almost all the parts to supply me with a built engine as he does not want any money for the parts and all I have to pay for is pistons diff and push rods. so it made more sense to me to simply go for the 1380cc.

 

Thanks Ryan

[lyesryan]

The use of the car will be for both road and track use as the company I work for hosts the GTROC Sprint Series so I am almost always able to attend in the guest classes. so I want it to be capable of being competitive with the bigger more powerful cars.

 

Thanks Ryan