Inliners International Forums General Discussion Hi Performance Doubts about chevy 250.

Augusto,

Several comments:

1. Recommend purchasing the new 2nd Edition of "Chevrolet Inline Six-Cylinder Power Manual' by Leo Santucci.

2. Boring to 4" cylinders can result in thin cylinder walls. This is performed some, though generally for specific racing engines. Do Brazilian cylinders blocks typically run thick or thin? Check some of the previous threads on this forum board. Search using "Mexican" helps as the Mexican 250's had thicker cylinder walls and are frequently mentioned in the discussions on boring and cylinder wall thickness.

"boring out a 250" started by Al on 05/15/09 #49941
"Max Overbore for 250" started by JeffF on 06/25/10 #58727

If you elect to use the 4" bore then Chevrolet 327 pistons will work. A small selection of stocked pistons will be available both cast and forged. 327 pistons are available for use with both 5.7" and 6" connecting rods. Forged pistons are available in both the 2618 Aluminum alloy (typical forged aftermarket choice) frequently use for high horsepower applications, and 4032 Aluminum alloy (typically in OEM forged performance applications) which runs tighter clearances.

3. You can use either the 5.7" or 6" rods. Small block V8 rods are narrower on the big end (crankshaft end)and will not work. They must be for the Chevrolet inline 250. As mentioned before, OEM stock 5.7" and 6" rods are used in Brazil. In the USA 5.7" and 6" aftermarket connecting rods for the 250 are available from SCAT and Crower.