[frank.g]

Interesting observation. Steve Schappaugh has had many SD's over the years, and it has been a long while since I have seen any of his, so I don't know to which car the observation is referring to. It's an open ended statement, so I can't tell from it whether Steve has a pre-production car, whether he retro fitted an early system to his car (unlikely as that would be) or whether he got the one that slipped out the door. I have learned thru the years with GM to never say "never". But, I will say, for all my years that I edited the SD Registry, none of the cars registered were built prior to the cutoff date that the emission system switch occurred.

[johnta1]

That blurb from the text under the picture was referring to the fact that the SD was different than the early engines I think?

Here is what was in the article later on:

Discussing the emissions system of the Super Duty 455, McCully stated that preproduction SD engines with the 041-spec camshaft such as those found in the engineering test mules and press cars should have had the first-type system. But EPA certification for a cam change delayed the SD's release until late April 1973. Since the changeover to the second-type system occurred prior to that, it is unlikely that any production SD engines received the first-type system.

The thread on Micheal's 'test' TA probably had the 1st version egr.