The op's pics are shown with the correct rockers for the 1786 1970 heads,...undoubtedly at somepoint I. It's future a head took a **** and the replacement head recieved the original rockers,..no reason not to,..then out the door it went,...fact is steel rockers didn't come out till 1972 and some made it on engines in very late 1971,....If you took your 1970 GS 455 in for service in 1974 for noisy rockers you would have received the steel replacement
I notice in the pictures that BOTH the intake and exhaust valves are unshrouded, makes me believe these were converted after the fact, I’ve only seen the intake valve unshrouded in Factory Stage1 heads…….am I wrong or blind?
Both I and E were done. I can only relay second hand info from comments of an old friend of mine who was a quality inspector where the heads moved off to get the Stage 1 valve conversions done. The cutters were a one-piece deal, made to open the chambers and cut the larger valve seats in one step, one for intake, one for exhaust. Complaints from the folks doing it were that it was a pain in the butt, cutters got worn out. Hearing this it wouldn't surprise me if the results changed over time until the next set of cutters came on. How frequently that happened, and how much was scrapped because of cutter wear we'll not know. A good guess from an efficiency standpoint is that they may have run a LOT through on new tooling, then shelved them and said "no more of this". Devon
Does the unshrouding on the ends of the combustion chamber on OP's heads look to be a bit more than the ones taken of the line?
Sorry, to me it looks like the offline procedure was done, and if they had the new cutters in place and ran a bunch, this is likely what we're seeing here on a service replacement cyl head. Of course the scientist in me says "let's see combustion chambers over time", but that won't happen. On a side note: later, Riviera got the big valves too, but no unshrouding of the chambers! I have no idea what was up with that. Somewhere I have photos of the original cutters, probably a Kenne-Bell publication. Gotta do some looking. Devon
Cool, would like to see these photos! The only thing I can think off the inconsistency of big valve heads without shrouding is the GS Stage1 package was the only motor to get all the good stuff?? Off the subject of Buicks "forgive me"! wondering how Oldsmobile worked the bigger intake valve on the W30 heads? or even Pontiac. I'm guessing Chevy made so so many they had their own production line for the good heads.
