Cylinder Wall Thickness
Turbo Mini Forums

I've just been comparing the cylinder wall thickness of 998 and 850 blocks.

The 998 appears to have a cylinder wall thickness of approx 7.5mm, whereas the 850 is approx. 6.5mm.

The 998 block will be much better, although some 850 blocks have been taken out to 68mm.

I'm planning on a 0.120" overbore, giving a bore of 67.6mm. This would be offset 0.025", maybe more.

This will take the cylinder wall thickness down to around 5.4mm at the thinnest point. This sounds like plenty to me.

I would like to go a bit further, but I'm not sure of the limit.

Does anyone know how much cylinder wall thickness you actually end up with on an offset bored 1380?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

In the Netherlands someone claimed to have 76mm pistons in a big block(offset: 1mm outer, 0.5mm inner) with 2.1mm cylinder wall thickness.
He had to sleeve oil lines.

For 1380 he claims 4.2mm (using same offset as above)

If your Dutch is OK: http://www.minisevenclub.nl/forum/viewtopic.php?t=19780

So a 998 with std bore spacing should be safe with 67,88mm or even 69,88mm

Anyone with a 1380 ever measure the cylinder wall thickness?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."