Bob, If the engine coded TA (correct 71 Riv GS) is Stage 1 engine, should I use initial timing 10 deg. ? On the label under the hood, it is written 4 deg., but in a 71 book, for Stage 1 is 10 deg..... Of course there is no warranty that I have correct label under the hood - somebody could use repro label over the years. Any ideas which initial timing is correct ? EDIT: I was checking also the document: Buick 1971 Engineering Features and AMA Specs © GM Corp , on page 34 it looks like they named Stage 1 only for GS models, while for Riviera GS, something like "higher-powered version of 455". But no mention of Stage 1 in Riviera. Then 4 deg. of initial timing from my label, would be correct.....