see where they go wrong on there is 1985 -86 ,, in those years the tpi lb9 and l69 had the compression ratio at 9.5.1 while the lg4 was at 8.6.1 ,i was in an argument yesterday on this topic but from my 1986 pontiac owners manuel thats what it says,, i'm not sure from 87 and on what it was , can someone please let me no about the 87 cr thanks

 

I do know that in 1988 the compression for the 5.0 and 5.7 TPI was only 9.1:1

 

according to here

https://www.thirdgen.org/newdesign/tech/techdb.shtml

all 87 v8's had a 9.3:1 cr..