Vintage Truck: Peterbilt 354DT Hauling Load Of Giant Logs Powered by OHC Hemi-Head Hall-Scott Gas Engine – More Power Than A Wimpy Diesel

Dman sent me another vintage shot of an early Peterbilt, and this one is a monster, in more ways than one. It’s an extra-heavy duty model 354DT, part of a fleet bought in 1948 by Feather River Pine Mills, located in Northern California. They were obviously harvesting giant old-growth pine trees, and needed powerful trucks to haul them out of the remote logging sites to the mills.

And they chose to have them be powered by Hall-Scott gas engines, the legendary OHC hemi-head torque monsters that generated significantly more torque and horsepower than the naturally-aspirated diesel engines of the day.

The 400 series was the post-war successor to the Invader and other legendary truck, bus, marine, airplane and rail-car engines built by the pioneering high-power firm of Hall-Scott, located in Berkeley, CA. The big inline six had a 5.75″ bore and a massive 7″ stroke, for a displacement of 1091 cubic inches (17.9 L). Hall-Scott engines produced their massive power thanks to a hemi head with an overhead cam, allowing excellent breathing. This was at a time when most truck (and car) gas engines were flatheads.

Here’s a dynamometer chart of a H-S 400. Peak output was 950 lb.ft. @1300 rpm, and 295 hp @2000 rpm. The big Cummins diesels back then made between 160 and 200 hp. It wasn’t until diesels were turbocharged that they could equal the power outputs of a H-S gas engine.

Update: the first chart is for a gas engine version using 73 octane gas. Here’s the one in for the butane fueled version (as used in these log-haulers) that makes 965 lb.ft of torque and 310 hp, thanks to a higher 7.1:1 compression ratio to take advantage of the higher octane of butane (LPG).

In the post-war era, there was a rapidly growing demand for larger trucks, higher speeds and more power. The greater efficiency of the diesel was very compelling, and diesels quickly gained market share.

But there were holdouts. Some operators, typically in the West, where mountains slowed down diesel trucks significantly, were willing to accept higher fuel costs for the higher average speeds that Hall-Scott engines delivered.

There were even a few operators that installed Hall-Scott’s giant V12 engines, capable of making 500-900 hp.

One reason some operators in the West kept running H-S engines into the ’70s was that they could be specified to run on butane, which was a byproduct of oil refining, and often available quite cheap back then within the proximity of a refinery.

And that’s what the Feather River Mills Peterbilts were burning (I found some additional info and images on this fleet of trucks at a post on them at Because of all the power they made, and being intrinsically less efficient than a diesel, one downside of H-S engines was their ferocious output of heat, making the cabin floor a burn danger.

But the bellowing, thundering sound of the Hall-Scott at full chat was described as “awesome” by one of the drivers, even if he did have to stop and soak his leather boots in the river to keep from burning his feet as he pushed his trucks wide open up the steep grades. It gives new meaning to the expression “hot-footing”.

I have been promising a full write-up on Hall-Scott, which has a fascinating history going back to the very early days of the automobile. And I will do so this winter.


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Related reading: CC Tech: Why Gas Engines Intrinsically Make More Power Than Diesel Engines