Originally Posted By: DeuceCoupe
Hank,
Yup now I remember. The drill bit for a 350 Chev is about 1/8", so a perfect 350 block with no core shift would have a cylinder wall thickess of
(4.400-4.000-.125)/2 = .137" - .020" roughness = .117"
So at 30-over your 350 walls would be .102" thick, maybe even .082" if you had some core shift.

The 230 six I measured had a 13/64 drill slip in between cylinders thru the freeze plugs. So at 4" bore, the wall thickness would be
(4.400-4.000-13/64)/2 = .100" - .020" roughness = .080"
So a Six bored to 4.000" would have walls of .080" in a PERFECT block with no core shift, and as thin as .060" in a more typical core shifted block. That's too thin.

So the 230 cylinders ARE cast thinner than 350v8 cylinders.
Not sure on the 292, I will see if I measured any.

Not that any of this affects Mitch, he just needs a 250 crank!


Yeah, the thickness between the cylinders is thin, but more importantly is how thick it is on the cylinders thrust side. Because of core shift and the shape of the cylinder barrel is often cam shaped, the cylinder walls are often between .150"-.180" thick on a non-Mexican block, but i've seen then way thinner before boring also. The Mexican blocks are often as thick as .230" or more(depending on core shift on the thrust side). So after an overbore, as long as you are still above .125" thick on the thrust side, this will be acceptable for a performance or race application. Filling is also better if your toward the low side of thickness.


Class III CNC Machinist/Programmer