Hi, Bruce P.
I could be wrong but I think that most if not all of the stretched D8s that went to Antarctica were turbo-ed for 'normalisation' as they would be required to operate at altitudes in excess of 10,000 feet, maybe as much as 12,000 feet, on a trip to the South Pole. The first of those, Mary Ann, was built in 1953 and I think the last one came off the line with a turbo-ed D353 engine in 1958-9.

The 14A and 15A as standard were naturally aspirated but the first D8Hs came with a turbo, at least to the best of my knowledge.

The later 17A D7s were turbo-ed and earned the nickname, "Whistler D7", due to their distinctive whistling sound as the turbo wound down. I don't have the date or serial # for the switch.

Just my 0.02.

Hi Team,
from what I can see looking in my Caterpillar Used Equipment Playback book it would seem to be circa 1955 for the turbocharger introduction.
This year saw the 17A D7 come with turbo as standard and the DW20 & DW21 Scraper Tractor with the upgraded D337F had the turbo fitted too.

Several Cat engines before this year were Roots Supercharged such as the D337, D397, and the D375.
More searching may find one or two others.
Cheers,
Eddie B.

Look’s good Bruce, is that blade one of the ones built at General Tractor in Pomeroy?

Thanks Mike.  I think this is a later Holt blade.  The blades built at General Tractor were called Star. I think they were built in the late 40s early 50s.  David Ruark in Pomeroy has the information on them.  

Got it home today. SN 78A 3707.

That's a nice looking D4!