Engine rebore / resleeve

[pskipper]

Hi,

Which is better re-boring or re-sleeving? I have a chance to get NOS low comp pistons std for re-building Rosies engine and would like advice.

Thanks

Philip

p.s. any suggestions as to how much each option would cost?

[ian-s]

Unless youare getting the low comp pistons for free just go for a rebore it'll be cheaper.

[pskipper]

They're about a third of the price, or would be if these pistons were still available!

[bmcecosse]

To fit sleeves they would first have to bore out the block (more so than a rebore) - then fit the sleeves - then hone the sleeves out to the correct size. This is always going to be an expensive business - very much more than the cost of a simple re-bore. Especially if you consider the cost of buying sleeves - and are they readily available anyway ? Is this for a 948 or a 1098 engine ? I ask because the 948 can be bored + 65 thou - and std Mini 998 pistons used with either Mini or 1098 con rods. Might be a cost effective option.

[pskipper]

It's for a 1098 low compression engine (she's an ex police car) I now understand why the resleeve is much more expensive! Thanks

[bmcecosse]

Ahh - but there is no reason to keep it low compression - just use normal pistons - they don't seem too bad from Bull Motif. But some machine shops won't do the boring unless they can also supply the pistons - and rip you off for the pleasure !!
May be better to get another engine and 'do it up' - then just swap over.

[pskipper]

She's currently got a 948 in her, while not perhaps the most economical option I'm wanting to keep the original block etc for the historical value. I'm planning on trying to get a bit more oomph out of her with a 12G940 head when I recondition her (keeping the original head so that if wanted I can resturn her to original police state). What I don't know is whether there would be much of a difference between a HIF38 or a HS4 or HIF44 with that sort of setup as I'm only just getting into this?

[bmcecosse]

For a 948 the 38 HIF is plenty. But try to get hold of at least a 1098 camshaft (AEA 630) to fit when doing up the engine - better still - an MG Metro cam which also uses the much better bigger capacity oil pump which you will (??) be replacing anyway.

[pskipper]

The 948 is just a stop gap measure, my main plans are for the 1098 when it's rebuilt (new oil pump will be on the list of things to do) as then Rosie will be becoming my daily driver (have a little citroen AX diesel at the moment). Thanks for the info on the 948 though as when Rosie has finished with it I have some kit car/self build plans

[bmcecosse]

Your Minor will consume about twice the fuel of your AX diesel - unless you convert it to run on LPG of course.

[Onne]

then it will use even more fuel, but it's half the price

[bmcecosse]

It 'may' use about 10% more fuel - because LPG has a 10% lower calorific value (although there can be balancing efficiency gains because of the higher octane rating of LPG) - and at the moment up here in écosseland LPG is considerably less than half the cost of petrol.

[Onne]

That is what I said, I don't know the price of LPG in scotland (around 48p here), but I do know petrol is stupidly expensive.

[bmcecosse]

LPG is ~ 40p here although petrol has fallen to 92.9 - temporarily i'm sure. Because the LPG has ~ 108 octane rating - it can be used with a very high compression ratio and can therefore recover the 10% calorific value loss. So the engine doesn't necessarily use any more volume of fuel if set up correctly.

[Onne]

I didn't know that. I do know you need hardened valves and seats

[bmcecosse]

Oh yes - just like unleaded petrol. But for relatively low mileages it will be ok. Best bet is to grab an unleaded head from a Mini.