15 replies to this topic

[GAGSINIO]

Having had the Headgasket go twice in a year and slightly oval cylinders and knackered pistons, have decided to rebore out to 1340. Could you give me a rough idea of the cost, will go for mega pistons etc. just would like the rough estimate of the cost of the rebore?
Cheers,
G

[Cooperman]

I think you actually mean 1330 cc, which is +0.060" overbore.
Good pistons for this are Hepolite 21253-60.
Prices for re-boring vary, but allow around £25 per bore to go to +0.060".
However, you need to do a 'trial-build' after boring and thoroughly cleaning the block out to see how it all goes together. Then measure how far down from the block deck the piston crowns sit at TDC. Machine that amount less 0.005" from the block deck to bring the pistons to 0.005" down the bore. Cost for that will be around £25 to £30, but you'll have to take the block back to the machine shop.
A crank grind will set you back about £40, but will be worth it if the crank journals are scored or badly worn.
To do the 'trial-build' I have some old gudgeon pins which I've linished down a small amount so that they will just slide nicely intyo the new pistons and con-rod small ends. That does make life easier. You can use the old gudgeon pins fron the existing pistons after you get the machine shop to press them out.
PM me if you want a build sequence.

[Pigeonto]

Having had the Headgasket go twice in a year and slightly oval cylinders and knackered pistons, have decided to rebore out to 1340. Could you give me a rough idea of the cost, will go for mega pistons etc. just would like the rough estimate of the cost of the rebore?
Cheers,
G

I can tell you exactly. Mine was 125 plus Viciously Added Tax.That included refacing the top surface just to true up. Dont forget it takes more than one cut to take that much out and the bore centres need moving so its more than just a standard rebore out to the first oversize....................EDIT OOPS just noticed 1340!! The above refers to my 1380

Edited by PIGEONTO, 28 June 2011 - 09:46 PM.

[Cooperman]

Having had the Headgasket go twice in a year and slightly oval cylinders and knackered pistons, have decided to rebore out to 1340. Could you give me a rough idea of the cost, will go for mega pistons etc. just would like the rough estimate of the cost of the rebore?
Cheers,
G

I can tell you exactly. Mine was 125 plus Viciously Added Tax.That included refacing the top surface just to true up. Dont forget it takes more than one cut to take that much out and the bore centres need moving so its more than just a standard rebore out to the first oversize....................EDIT OOPS just noticed 1340!! The above refers to my 1380

The fact that at 1330 the bore centres don't need offsetting and you will only gain 2 or 3 bhp by going from 1330 to 1380 (the limitation usually being the head) is a really good reason for going to 1330. At 1330 you can still go to 1360 and then to 1380 without scrapping the block.

[icklemini]

If you wish to go out to 1380 in the future, then its worth offsetting if you are going 1330 now. Simply because there isnt enough meat left to offset bore a worn out 1330 to 1380 and clean up the bores....

[Cooperman]

If you wish to go out to 1380 in the future, then its worth offsetting if you are going 1330 now. Simply because there isnt enough meat left to offset bore a worn out 1330 to 1380 and clean up the bores....

I'm sure that's best, but a well-known 'Mini engine place' will offset bore to 1360 or 1380 from non-offset 1330. I've never seen the results, but the claim is it's OK. Personally I believe in sleeving back to 1275 from 1330 to save another A-series block from boring to destruction. I'm about to do that with a 1330 Mk. 1 Cooper 'S' block for a historic rally car. After all they'll never make any more.

[bruders 338]

I think you actually mean 1330 cc, which is +0.060" overbore.
Good pistons for this are Hepolite 21253-60.
Prices for re-boring vary, but allow around £25 per bore to go to +0.060".
However, you need to do a 'trial-build' after boring and thoroughly cleaning the block out to see how it all goes together. Then measure how far down from the block deck the piston crowns sit at TDC. Machine that amount less 0.005" from the block deck to bring the pistons to 0.005" down the bore. Cost for that will be around £25 to £30, but you'll have to take the block back to the machine shop.
A crank grind will set you back about £40, but will be worth it if the crank journals are scored or badly worn.
To do the 'trial-build' I have some old gudgeon pins which I've linished down a small amount so that they will just slide nicely intyo the new pistons and con-rod small ends. That does make life easier. You can use the old gudgeon pins fron the existing pistons after you get the machine shop to press them out.
PM me if you want a build sequence.

if you could with a build sequence. that would be a great help for me also.

[Cooperman]

After all they'll never make any more.

I wouldn't be to sure of that, if I was you cooperman

Ah ha, what do you know that I don't? New castings - Mk.1 Cooper 'S' type maybe. Now how good would that be?

[Cooperman]

I think you actually mean 1330 cc, which is +0.060" overbore.
Good pistons for this are Hepolite 21253-60.
Prices for re-boring vary, but allow around £25 per bore to go to +0.060".
However, you need to do a 'trial-build' after boring and thoroughly cleaning the block out to see how it all goes together. Then measure how far down from the block deck the piston crowns sit at TDC. Machine that amount less 0.005" from the block deck to bring the pistons to 0.005" down the bore. Cost for that will be around £25 to £30, but you'll have to take the block back to the machine shop.
A crank grind will set you back about £40, but will be worth it if the crank journals are scored or badly worn.
To do the 'trial-build' I have some old gudgeon pins which I've linished down a small amount so that they will just slide nicely intyo the new pistons and con-rod small ends. That does make life easier. You can use the old gudgeon pins fron the existing pistons after you get the machine shop to press them out.
PM me if you want a build sequence.

if you could with a build sequence. that would be a great help for me also.

Give me a week or so, then PM me with your email address and i'll send a copy if that'sOK.

[bruders 338]

I think you actually mean 1330 cc, which is +0.060" overbore.
Good pistons for this are Hepolite 21253-60.
Prices for re-boring vary, but allow around £25 per bore to go to +0.060".
However, you need to do a 'trial-build' after boring and thoroughly cleaning the block out to see how it all goes together. Then measure how far down from the block deck the piston crowns sit at TDC. Machine that amount less 0.005" from the block deck to bring the pistons to 0.005" down the bore. Cost for that will be around £25 to £30, but you'll have to take the block back to the machine shop.
A crank grind will set you back about £40, but will be worth it if the crank journals are scored or badly worn.
To do the 'trial-build' I have some old gudgeon pins which I've linished down a small amount so that they will just slide nicely intyo the new pistons and con-rod small ends. That does make life easier. You can use the old gudgeon pins fron the existing pistons after you get the machine shop to press them out.
PM me if you want a build sequence.

if you could with a build sequence. that would be a great help for me also.

Give me a week or so, then PM me with your email address and i'll send a copy if that'sOK.

Top bloke many thanks

[JakeJakeJake]

Cheapest short block you can buy is about £800 if that's any use, is an exchange so you give them your old one or pay a surcharge

[MRA]

After all they'll never make any more.

I wouldn't be to sure of that, if I was you cooperman

Nail on head

[MRA]

Cheapest short block you can buy is about £800 if that's any use, is an exchange so you give them your old one or pay a surcharge

If you want cheap.... however if you want quality parts then you will have to add a little more to that price....

And what is this total rubbish about 1380's only producing 2 to 3 bhp more than a 1330 ??? on a similar build expect at least 5bhp more than a 1330.... and more to the point the increase in torque you will get with a 1380 will absolutely massacre a similar 1330... Peter just because you don't like 1380's there is no need to "play them down"

And yes my figures are from a dyno session..... and no it wasn't a race engine , but a fairly moderately tuned road unit..

Edited by mra-minis.co.uk, 29 June 2011 - 02:52 PM.

[Cooperman]

Cheapest short block you can buy is about £800 if that's any use, is an exchange so you give them your old one or pay a surcharge

If you want cheap.... however if you want quality parts then you will have to add a little more to that price....

And what is this total rubbish about 1380's only producing 2 to 3 bhp more than a 1330 ??? on a similar build expect at least 5bhp more than a 1330.... and more to the point the increase in torque you will get with a 1380 will absolutely massacre a similar 1330... Peter just because you don't like 1380's there is no need to "play them down"

And yes my figures are from a dyno session..... and no it wasn't a race engine , but a fairly moderately tuned road unit..

If you just take a given 1330 engine and simply just go to 1380 without changing anything else you won't gain more than a couple of bhp. Now, if you increase the inlet and exhaust valve sizes and maybe the inlet tract in the same proportion to permit the breathing to increase in capability by the same percentage as the capacity increase you will see a proportional increase. From 1330 to 1380 is around 4%, so if the 1330 is giving 100 bhp, with proportional improvements to inlet & exhaust capabilities, you could expect a 4 bhp improvement. That's assuming a straight line capacity:power graph, but most graphs relating to performance always seem to flatten, not steepen (unfortunately). Torque could also be expected to increase by the same percentage.
Now, if you use the larger capacity to allow for a 'hotter' cam without the usual loss of bottom end, then your 1380 could start to pay off, but not many actually do that. Rather they just go to 1380 because it is seen as the easy thing to do.

It's not that I don't like 1380 engines. If done properly they are great, but I am aware that when a block is offset-bored to go to 1380 it is not really possible to save that block in future by sleeving back as the distance between the middle cylinders is too thin for sleeves. If new as-original blocks are going to be re-cast (for sensible money) then some of this does not apply, but I do still think that spending all that money on offset-boring for just a small power/torque gain is not cost-effective, except for the machining companies, for ordinary road Minis. For racing where every 1 bhp counts it's a different matter obviously.

[MRA]

If you just take a given 1330 engine and simply just go to 1380 without changing anything else you won't gain more than a couple of bhp.

Don't tar the rest of the Mini community with your figures Peter.....