The 8.6:1 heads have a larger combustion chamber volume than the high compression heads.
Pontiac regulated the compression by modifying the heads, not the pistons at that juncture
What is the casting number on your heads?
__________________
1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
|