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MG Midget and Sprite Technical - pistons on 948CC

Hello,
To continue an old thread.
Do you think it is technicaly possible to overbore a 948 + 0.06 (2.537") to 998 cc (2.543").
Or do I need to go to 998 + 0.02"?
My bloc has no vertical strip, but only horizontal ones.
It smokes a lot, even with new rings on +0.06 pistons.
Laurent
ld derancourt

OH... I've forgotten,
I can feel the horizontal stripes with the nail of my finger. I don't know if it is normal.
ld derancourt

Laurent-
Most unlikely that boring .006 will work, since any wear or other issue would require greater OS. Possibly it could be honed, but unlikely if you can feel discrepancies.

This: "My bloc has no vertical strip, but only horizontal ones." is not good, there should be no such ridges or grooves. Can you describe them better, or pics?

FRM
FR Millmore

a photo of the cylinders. I don't know if it coul help:

ld derancourt

Not enough light in the right places. Put a light under the block so that it shines on the cylinder walls.

If there is a perceptible ridge at the top, you are already at or pas .006".
The usual cause of ridges/grooves around the cylinder is heavy wear at the point each ring stops in its travel; or rust pits where the rings were during a long layup. Either will be beyond .006".

FRM
FR Millmore

Block is not completely dismantled and it is evening here in France, so difficult to do good photos.
I think the best way is to overbore up to 998 + 0.02, so an overbored of 0.026".
I just have to find pistons and conrods at the right diameter.
Thanks a lot FR.
Laurent
ld derancourt

This thread was discussed on 30/04/2012

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