12 replies to this topic

[cradley-heathen]

i have been offered an engine by a friend that has been split (gearbox, head, engine) and im wondering if its any good to me.

 

the bores are worn/crudy and it is currently +0.60, (pistons are marked 21251 +0.060) its a pre A+ block (dont know if that makes any difference?)

 

my questions are.........

 

1)

if the bores will clean up with a hone, are those pistons any good? (i kinda think they arnt the best from memory as they are low compression jobbies i think?)

 

2)

assuming i cant hone the marks out, can the block be machined to 1380 and still clean up?

 

 

 

the gap between the bores is currently as follows.....

 

 

 

{front of engine}                                                                                                                {flywheel end}

 

(cylinder1) <---5.1mm gap--->(cylinder2)<---4.4mm gap--->(cylinder3)<---4.8mm gap--->(cylinder4)

 

 

 

hope you can follow my description above!

[johnnyblaze]

yeh you can , same problem i have mines at 060 , im going to offset bore it and put in 094 pistons makes it 1360cc, that way you still have the 73.5mm rebore up ya sleeve

[cradley-heathen]

i didnt know you could still get +0.80 pistons as minispares dont seem to list them, i would be happy to just go another 20 thou to prolong the life of the block and as you say, keep 1380 for a final bore further down the line.

[GraemeC]

Don't think you can get +0.080", but you can get 73mm

[cradley-heathen]

Don't think you can get +0.080", but you can get 73mm

i see, i will look into that size then!

[GraemeC]

Although it looks like MS have stopped doing them now and have come up with a 72.5mm now:
http://www.minispare...|Back to search

Edited by GraemeC, 13 May 2013 - 06:40 PM.

[BritishRacingGreen]

Why not get it linered and save another 1275 block? As it's not an all out racer it really wont make that much difference.

[johnnyblaze]

if its not and all out racer then putting liners in and new pistons is a bit of an expense , when ya can offset bore it put 094 pistons in and you would get 100 000 miles out of it then rebore to 1380 thats a lot of life for a motor

[cradley-heathen]

i know what you mean about having it linered, but im sure i will get enough life out of it as it is, i would hope its going to last after this build!

[Cooperman]

If going bigger than 1330 (i.e. +0.060") you really do need to offset bore to get sufficient clearance between the cylinder walls on cylinders 2 & 3. That is expensive and will lead to another scrap block eventually.

I just did an Innocenti engine which was at 1330 and needed a bore. I had liners fitted and it bored back to 1275, using 21253 pistons with the block decked to bring the pistons right to the top of the block. That really is the proper way to do it and the engine can then be re-bored to 1293, 1310 then 1330 cc, before re-sleeving is again required. Doing that you won't have head gasket issues or thin block wall problems.

[Earwax]

73 mm pistons from a Mazda (Mx5 from recollection) will also do the job

[johnnyblaze]

If going bigger than 1330 (i.e. +0.060") you really do need to offset bore to get sufficient clearance between the cylinder walls on cylinders 2 & 3. That is expensive and will lead to another scrap block eventually.

I just did an Innocenti engine which was at 1330 and needed a bore. I had liners fitted and it bored back to 1275, using 21253 pistons with the block decked to bring the pistons right to the top of the block. That really is the proper way to do it and the engine can then be re-bored to 1293, 1310 then 1330 cc, before re-sleeving is again required. Doing that you won't have head gasket issues or thin block wall problems.

 

hey cooperman, whats the cost difference of sleeving then boring opposed to offset boring, i was going to bore mine to 094 1360 but now i might just get some new 060 pistons run that and then after its toast resleeve i like the sound of saving the block especially if you go get 4bolt mains done or somthing

[Cooperman]

The advantage of sleeving is that it 're-lifes' the engine back to as original with the normal re-bore sizes then available.
For a classic car that is the very best way to go as the future shortage of blocks is just starting to be obvious and there will never be any new blocks cast (despite what you might hear) at affordable prices. So as a classic car movement we need to preserve our cars for the future and re-sleeving does just that.
Mini Spares sell a range of sleeves and a sleeve-and-bore job should cost around £300 plus standard 21253 pistons. If you measure carefully you can get the block decked to suit the new pistons at the same time and you end up with an engine as near the original as it's possible to get.
In fact it's a 'win - win' situation compared with offset boring with a potential scrap block, or one which would be very expensive to restore later on.