hey guys, what did GM do to change the compression ration of the LG4 engine in 1985. it went from 8.6:1 to 9.5:1. did they change the heads, or the pistons? i may be doing an engine swap with a friend and this will help us decide what we can and can't do with our motor.

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86 IROC-Z
305 TPI
700R4 W/ shift kit
3.23 gears
T-Tops
maroon with gold stickers and rims/ black interior
43,000 miles
flowmaster exhaust, edelbrock headers, gutted airbox, converter, and MAF, K&N filters.

soon to come are 3.73 gears and subframe connecters.

 

The early low compression LG4's had dished pistons, later ones had the same flat-tops as the L69.

 

cool thanx for the info. that is what i suspected, so then is there a difference between heads on any 305's? or are they all the same. obviously they switched to centerbolt in 87 but before that there was only one head casting right?

------------------
86 IROC-Z
305 TPI
700R4 W/ shift kit
3.23 gears
T-Tops
maroon with gold stickers and rims/ black interior
43,000 miles
flowmaster exhaust, edelbrock headers, gutted airbox, converter, and MAF, K&N filters.

soon to come are 3.73 gears and subframe connecters.

 

All had the same heads.

 

cool thanx for the info man.