26 replies to this topic

[edjohnson]

Basically im gonna rebuild the MG metro engine in the shed

If i decided on inspection i didnt have to get a rebore, and new pistons, i was gonna keep it 1275cc.

Im probably gonna have a sw5 cam, roller tip rockers, double valve springs, possibly a slightly modded head, stage one kit etc

How much do i really need the extra displacement?

If it looks worn, then yeh, cool, ill eith have a 1293 or 1320 or something along those lines.

But if it doesnt physically NEED a rebore, then what will i miss really?

I dont want to spend too much on the engine if it can be helped.

Cheers

Ed

[Chewy]

Hi

IT DEPENDS ON IF YOU USE THE CAR EVERYDAY IF U DO A 1293 WOULD BE OK BUT IF YOU ONLY USE IT AT WEEKENDS A 1380 WOULD BE A POSSIBLE OPTION

IF U DO A 1380 MAKE SURE THAT IT IS OFF SET BORED IF U DONT IT WILL GO THROUGH HEAD GASKETS A LOT

Edited by Chewy, 26 November 2006 - 11:54 PM.

[Don't Panic]

I beleive the cam will have more effect on driveability than the bore, I'm no expert on cams but i think the sw5 is a well proven fast road cam, so you should be fine driving everyday with that setup.

I'd say that if your looking at getting new pistons then you might as well overbore, 1293 or 1380 theres plenty threads on the topic, if your can rebuild the 1275 with the same pistons you'll save allot of money but really theres no replacement for displacement... you'll see more benefit of your other mods if you've more capacity!

Also i'd consider a re-bore before head mods... both are fairly expensive but you can change the head later on without removing the engine again.

Thats just my opinions, theres lots of opinions, but the best would be to ask people for a ride in there mini's and see what you prefer.

[Jammy]

The extra displacement will give you more torque (which also depends the cam, rockers, head, etc).

As above, depends what you want to use the engine for. Personally I'd either go for a 1293 or save the money spent on new pistons and keep it 1275.

[edjohnson]

Thanks for the input.

If I do need a rebore it will probably be a 1293 or 1320/1330.

Is there much difference between a 1293 or a 1320?

It will be a second car, but will probably be used for long journeys occasionally, and going to work regularly.

I want something with enough power to keep things exciting, and scare the Nova boys, yet retain drivability and reliability.

Am i on the right lines??

Cheers

ED

[Jammy]

Ok. Just an FYI, 1275 +20 is a 1293, 1275 +40 is a 1310, 1275 + 60 is a 1340. To get a 1330 you need an expensive stroked crank. I don't think there is such a cc as 1320.

[The Matt]

Ok. Just an FYI, 1275 +20 is a 1293, 1275 +40 is a 1310, 1275 + 60 is a 1340. To get a 1330 you need an expensive stroked crank. I don't think there is such a cc as 1320.

1330 is a +0.0060" and 1340 is a 73.5mm bore on a de-stroked crank.

[lew]

what bout a 1301 +30

[The Matt]

what bout a 1301 +30

Yup, there are plenty of options for rebore size. But you need to remember that it is easier and cheaper to go for more standard rebore sizes. Best place to look is on Minispares, you can get a good set of pistons reasonably cheap, but if you go for odd sizes it'll work out dearer.

I personally think that (as long as the block will take it) a 1293 is a good start and you can still make it into a screamer of an engine.

[Jammy]

what bout a 1301 +30

I don't think it quite works like that. The +number is the increase of size in thousands of inches over the standard size; 998, 1275, etc.

[The Matt]

I think there is a 1301 or 1302, +0.030" pistons are available, or at least they used to be back in the day!

[Jammy]

Ah right, I thought he meant a +30 on top of 1301! Erm, yea, I know +30 used to be available. Have a searc on MS I spose, although Simon is reading this as I type, so maybe he's about to enlighten us.

[Bungle]

Is there much difference between a 1293 or a 1320?

27 cc

[miniboo]

you can get 73 mm pistons now aswell which will make a 1275 into a 1360 i think it is +80 but not sure exactly

[fikus01]

the bigger you go with a re-bore the more power and torque your engine will have the capability to produce, but it will get closer to its limits and less reliable!! 1380's are tried and tested, they do have they're drawbacks when pushed hard if they arent offset bored (head gasket failure)

just look at what pistons you can get the cheapest and base the build round that!! doubt you'll need omegas unless you're going for seriously high power!!