Just purchased 71 RIV GS. Would like to know the skinny on this engine. I'm sure its 8.5 to one comp but I'm looking for an engine to completely rebuild and i'd like to know if this is a good place to start. What about the heads? Bernie Steffen zstef@mchsi.com
Bernie, Yes the 71 block is a good place to start. First of all the oil passages have already been enlarged. The compression is 8.5:1 you will need to change the pistons to the 70 version. Your machinist will also need to check the deck height of the installed pistons. The 71 Riv GS should have stage 1 heads but the chambers were a little larger than the 70 version. Everything will have to be CC'd to determine true compression. Just installing the 70 pistons in the 71 motor with the 71 heads and a .040" thick head gasket will probably yield around 9:1 compression. Good luck with your rebuild. Dave
71 Buick RIV GS Dave Thanks for the info. That was exactly what I wanted to know as I'm shooting for 9:1 Compression. I think its going in a 85 GN. I know its a waste but I can't make it run right with the six cylinder so its 455 time. I won"t cut it up or anything so I can pkut it back anytime I want to. Thanks again Bernie Steffen zstef@mchsi.com
the standard heads from 67-70 were 69cc and in 71 they increased to 71cc. stg 1 heads (if you've got em) have a reduced combustion chamber size due to the larger valves occupying an extra 3cc in the chamber. if you've got 1971 stg 1 heads your volume should be a respectable 68cc ... smaller than the standard 70 heads. so if you put in 1970 style pistons you should have over 10:1 compression.
