Donny, There was some discussion about this issue a few years ago. I had been told that all '70 GS Rivs came with Stage 1's, and while I don't believe that is true, I have been told that some did.... I am not enough of an expert to say one way or another, but it makes sense that at least a few of them were made. Dan
I've heard the controversy as well about the '70 Riv GS's having big valve heads, but there were no Stage 1 markings like on the '73 Stage 1 Rivs. I've got an all original 455 I pulled from a '70 Riv GS sitting on a stand in my shop. One of these days curiosity will get the best of me and I'll yank the heads...
Here's 2 cents. This was a ratings "game" back then ... Buick's bread and butter was the full-size sedan and lesser extent the full-size luxury sport coupe market and not the mid-size and compact markets, therefore, the larger cars were at the top of the marketing food chain even though in '70 the std. GS 455 (factory rated at 350 HP) and the Electra/Wildcat/LeSabre/Riviera engines (factory rated at 370 HP) used essentially the same engine/cam/heads. So to protect its most important market in the full-size cars, they garnered the most prestige in terms of advertised power ratings, hence the 370 HP for the Electra vs. 350 HP for the GS 455. What's up with that? The insurance horsepower rating game was also at play, but lesser at Buick compared to other brands. So, the Stage 1 in '70 at 360 HP? Uh huh ... right. Stage 1 heads were a main component of the package, but what the Riv owner here does not understand is that the Stage 1 was indeed a package of parts of which he probably only has the heads. Logic would dictate that significatly more than 10 HP was present for the whole package including the better breathing Stage 1 heads (and slightly higher compression ratio due to the displacement of the larger valves in the combustion chamber), more aggressive cam and other carburetion and ignition-specific upgrades ... a mere 10 HP ... to 360 HP (from 350 HP rating)? ... try starting instead from 370 HP and then add all the Stage 1 upgrades (I have heard for years a true rating of about 415 to 425 HP). But, I too have been told by many knowledgable Buick guys that the '70 Riv GS's are a good source for turn-key large valve heads of the Stage 1 package sans the other Stage-specific goodies like carb and recurved distributor. A good question is what other incidental parts of the '70 Stage 1 package may be present on the '70 Riv GS ... like possibly larger fuel pump, etc? I dunno.
Well I've got an untouched 455 from a '70 Riv GS sitting on a stand. I haven't torn into it but what I can tell you is that it has the standard 7040240 Quadrajet, no fuel pump on the block because of the electric pump and and the distributor isn't a 1112016. I'm curious about the heads, but they'll have to wait a while.
