28 replies to this topic

[Minimania93]

Looking to get a 1275 engine, and I'm looking to bore it. What would people recommend to bore it out to? Need this to be as detailed as possible I have problems understanding written stuff. Also what pistons would I need for it?
Cheers

[Carlos W]

Are you looking to rebore to produce more power?

 

The big limiting factor with an A series engine is the head, and bigger valves, correct compression ratio and porting and polishing will give you more of a gain than just reboring.

 

What do you plan to use the car for? Once you've answered this people will advise on cam choice etc

[alex-95]

I would go to  1293, theres no point boring it straight out to 1380 as the blocks scap after that.

[Alex_B]

There are standard sizes you can rebore to, 1293cc, 1330cc, and 1380cc are the most common, the largest 1380 requires the cylinder bores to be 'offset bored' which means two cyl's need to be offset slightly, this is to improve the longevity of the head gasket, this does however mean if the block needs to be bored out further due to wear it will require relining (a sleeve put into the bores) and then removing the offset can be tricky - hence usually not financially viable and a block scrapped. 

The gain over 1330cc isnt much so going the full 1380 is generally regarded as pointless for a road car, and personally I would go for 1293cc, thats what historic racing minis run (due to regulations) and they go well enough ;) 

 

[Minimania93]

Thanks for the quick replies. If I bored it out to 1293 would I require different pistons or would standard ones be Ok? And the same for 1330?
Cheers

[Carlos W]

Thanks for the quick replies. If I bored it out to 1293 would I require different pistons or would standard ones be Ok? And the same for 1330?
Cheers

 

re-bore would require different pistons

[Minimania93]

Carlos I'm looking for an all round bit of gain on performance really the car is going to be a show car really but would like it to have a bit more power as it stands really, looking for better acceleration, top speed and torque general.

[Minimania93]

Thanks for the quick replies. If I bored it out to 1293 would I require different pistons or would standard ones be Ok? And the same for 1330?
Cheers

 
re-bore would require different pistons

Cheers for that Carlos. If I bored it 1293 what pistons would I require? And is there anything else engine wise I would require?

[Carlos W]

+0.020

 

Minispares would be a good place to start, but as above, what are you hoping to achieve?? 

[Minimania93]

+0.020
 
Minispares would be a good place to start, but as above, what are you hoping to achieve?? 

Cheers I'm looking for an all round bit of gain on performance really the car is going to be a show car really but would like it to have a bit more power as it stands really, looking for better acceleration, top speed and torque general.

[Carlos W]

 

+0.020
 
Minispares would be a good place to start, but as above, what are you hoping to achieve?? 

Cheers I'm looking for an all round bit of gain on performance really the car is going to be a show car really but would like it to have a bit more power as it stands really, looking for better acceleration, top speed and torque general.

 

 

You're going to need some head work done, correct compression ratio and a decent fast road cam.

 

What's your budget?

[Minimania93]

 

+0.020
 
Minispares would be a good place to start, but as above, what are you hoping to achieve?? 

Cheers I'm looking for an all round bit of gain on performance really the car is going to be a show car really but would like it to have a bit more power as it stands really, looking for better acceleration, top speed and torque general.
 

 
You're going to need some head work done, correct compression ratio and a decent fast road cam.
 
What's your budget?

Not really had a look at budget yet just want to get basic idea of what I need to get first.

Quick question just had a look on Minispares at there pistons, and they have a selection going from +60 to +20 I'm guessing that the +20 is for 1293 +40 1330 and +60 for 1380. Please correct me If I'm wrong.

And what head work would be needed?
And what cam would you recommend?
Cheers

[KernowCooper]

First the bores need to be measured to see what the size in now, and that will determin what the next size of rebore will be and go from there.

[Minimania93]

 

+0.020
 
Minispares would be a good place to start, but as above, what are you hoping to achieve?? 

Cheers I'm looking for an all round bit of gain on performance really the car is going to be a show car really but would like it to have a bit more power as it stands really, looking for better acceleration, top speed and torque general.
 

 
You're going to need some head work done, correct compression ratio and a decent fast road cam.
 
What's your budget?

Also what's the difference in between dished and flat top mega pistons?

[oli8925]

Slightly larger bore alone will do little to help. As others have said getting the engine to breathe better and throw more fuel in will help much more. This means inlet, exhaust, head, valves, cam, even a lightened and balanced bottom end to help the engine rotate and rev will make a nice difference.

 

Have you got the 1275? Are the bores scored and does it need a rebore? If not - why bother?

 

If the car is only a toy/show car, consider changing the final drive and playing with the gearbox to get better acceleration.

 

 

 

Without meaning any offence, and it's good that you've come here to ask the questions, you need to read or find videos and websites that teach you how an engine works in basic terms and how changing this or the other will improve things. That's not meant as a dig and I'm sure no one here has a problem helping, but if you understood you'd be able to work out what step to go to next and what will make the biggest difference to your current set up.