Two Surviving Prototype Scout Diesels
The International Scout was diesel before diesel was cool. Diesels were nothing new for International Harvester, in their truck lines and, of course, in the agricultural and off-highway equipment lines. In the latter part of 1971, the IH sales department decided adding diesel power to the new Scout II was a good thing. That wasn’t a new idea either. Going back as early as the 1961 intro of the first generation Scout 80, International noodled the idea of diesel power. At that time, they had introduced a diesel option into their light truck line, the D301. We covered that in 2018 and you can see the story online at the link below. As far as the Scout was concerned, the early motivation was for export markets like Australia, where Scouts sold reasonably well. Then the Arab Oil Embargo happened in 1973 and added a domestic possibility with a new urgency.
International did their research and rounded up a number of suitable diesel powerplants to try in the Scout. All were of a similar physical size and weight and had similar sub-100 hp outputs. Our history of the engineering that led to the Chrysler–Nissan CN6-33 being chosen for large scale production is incomplete but we know parts of the story and have two running prototypes to learn from. This is a little bit of their story.
Test Engine- IH D301
The list of possibles started with an in-house candidate, the D301 six. Weighing in at 860 pounds and displacing 301 ci, it was an unsleeved truck version of the D282 tractor engine. It was the largest displacement contender and had the most torque. It made a respectable 92 net hp (112.5 gross) at 3000 rpm and 228 lbs-ft. It was a bigger and heavier than the other three, only a four-main engine. Having been designed in the late ‘50s, it was a decidedly antiquated design, a low-revver, and was winding it’s way out of the IH livery. Though we see it listed as one of the contenders, we have found no evidence so far that it was actually installed in a Scout. We’d very much like to find out if it was.
Test Engine- Chrysler-Nissan CN6-33
The first diesel we know was actually installed and tested in the Scout was the Chrysler-Nissan CN6-33 (SD-33 designation from Nissan) in 1973. It was a compact, four-main, IDI inline six displacing 198ci. It’s four-cylinder ancestors had debuted in 1964 and a six-cylinder variant had appeared by ‘68. It weighed in at a respectable 630 pounds. Nissan gave it a maximum rated output of 92 hp at 4000 rpm and 154 lbs-ft at 1800 rpm. An 80-86 hp rating at 3800 rpm was most common in automotive applications. Chrysler and Nissan had teamed up in 1969 to market the engines in the U.S. but by the time IH was involved, that relationship was winding down. There were a lot of Nissan power test rigs, as it was the engine selected for production.
Test Engine- Peugeot 6.90
Next up was the Peugeot XDP 6.90 “Indenor” engine. It was a 193 ci, indirect injected diesel with seven main bearings and wet sleeves. It was an offshoot of the long running XD/XDP series engines and was produced under license in other parts of the world. We see it listed as being produced from ‘67-82. Power output varied by application, with a common one being around 100 hp at a screaming 4500 rpm. Two Scouts were repowered with the 6.90, a well optioned green Scout II and a bare bones yellow one, both ‘74s. Both turned up at Alan Sheffer’s place (read on).The hulk of the green one survives, which is how we were able to get the VIN and identify it as a Peugeot test rig. When Alan acquired it in ‘75, the camshaft was broken into several pieces. The other one was a runner and was reportedly a pretty zippy engine.
Test Engine- Perkins 6.247
Finally we get to the Perkins powered Scout. At the time of International’s inquiry, Perkins had a number of six-cylinder engines available but the one submitted for consideration was a new one, the 6.247. It was so new that the engine installed in the Scout was a preproduction unit. In theory, it was a perfect fit. The engine had been designed for the light duty market and with North America in mind. Displacing 247 cubic inches, it was rated at 98 horsepower at 3600 rpm and 158 lbs-ft at 2000 rpm. It weighed in at 643 pounds. The 6.247 was indirect injected, had dry sleeves and seven main bearings. An early production 1973 Scout II was sent to Perkins’ U.S. facility in Farmington, Michigan, in September of 1973 and was ready for testing early the following year. It was the most powerful diesel tested in the Scout. The 6.247 went into production in 1975 and was sold around the world for light duty to light-medium duty application. It powered the Ford F100 in Australia for a year or two around 1980 but Perkins stopped building it in ‘82 by most sources. It was licensed to Mazda, who built it a number of years for truck applications. It saw service as a marine engine as well.
Test Engine- Mitsubishi 6DR5
On the list of engines to be tested was a Mitsubishi six, the 6DR5. This is another one we’d like to find. Ironically, it was the same engine used for the ‘78 and ‘79 Dodges in their first foray into diesel power. Regrettably, we have little documentation on them other than reports that two were installed for tests. The 6DR5 was in the same ballpark as the others tested, 100 horsepower at 3700 rpm and165 lbs-ft at 2200 rpm, from 243 cubic inches. It had seven main bearings, dry sleeves and was naturally aspirated with indirect injection. We did not find a weight spec for it but predict it was in the ballpark with the Perkins and the Nissan.
Survivor- 1974 Scout II Perkins
Surviving test mules and prototypes are unusual. That three prototypes in the same test program survive, albeit one as just a hulk, is miraculous. The Perkins powered Scout II was built as a 1974 model in October of 1973. It was ordered by Truck Engineering to be a test mule, so it had absolutely no frills. It was ordered with the base 258ci gas six backed up by the Warner Gear T-18C 4-speed manual and Dana 20 transfer case. Very low 4.27: axle ratios were specified.
The 6.247 engine was installed by Perkins in Farmington, Michigan, and the Scout was tested early in 1974. We have not seen detailed results of those tests but the engine was not selected… obviously. It’s not clear (and doubtful) that any serious faults were noted and given the extra power vs the Nissan would have been welcome. The only stated reason we have found was that IH thought Perkins would be unable to supply the engine and parts in sufficient numbers to meet their timeline to debut the diesel option for the 1976 model year. The info we have says that only one of these engines was installed.
The engine has no glow plugs and Mike Shaffer (read below) reports it was a bear to start in the Midwest cold. It had an etherizer on it. Perkins’ SAE paper from when the engine was introduced stated the Howard precombustion chamber would cold start unaided to -6C but would come with the aforementioned etherizer. The Mazda version of the engine had glow plugs, however.
What’s most interesting about this Scout and its engine, is that the engine was a preproduction unit. Perkins was just finishing up the development of the 6.247. The engine has a Roosa-Master (Stanadyne) injection pump on it versus the Bosch units that were more commonly seen later. After testing, the Scout was sold to the Alan Sheffer, an Indiana farmer who kept busy in the winter converting gas rigs to diesel. Sheffer actually bought all the test rigs. According to Mike Sheffer, son of Alan, after he had purchased it Perkins suddenly wanted it back. The story goes that 60 test engines had been built and this is the only one that was not recovered. Alan said they could have it back when he was done with it.
Back in 2017, noted tractor and truck collector/restorer, Wendell Kelch, who has a sizable collection of his own, ran across the Perkins Scout. It had changed hands a couple of times after the Sheffers and was found in Florida. By then, the body was beset with rust, though the Scout still ran well enough. Kelch put it in queue for a restoration at his shop. Kelch’s crackerjack paint and body specialist, Todd Bee, was soon seen cringing at the level of body repair necessary, so a minimally rusty ‘74 body was procured from out West. The mechanical parts didn’t need much work but were refreshed as needed.
The Perkins Scout II was ordered as a bare bones test rig in Glacier Blue with a Cab-Top (International’s name for their pickup cab), originally with a 258 gas six. The only options above the base build was the T18C 4-speed (more suitable for the diesel) and extra low 4.27:1 axle ratios. The low ratios on a diesel seem counter productive but we don’t really know their motivation for choosing them.
Survivor- 1973 Scout II Nissan
This survivor is the earliest known diesel test program Scout and the earliest know survivor. It retains much of its original pedigree as a test rig. Alan Schaffer bought the unit and sold it pretty quickly to a Portland, Indiana, are farmer who did very little to change it. It still has engineering department decals on it, emission labels for the test engine and a few test instruments. After the farmer passed on and his estate was sold, David Evans acquired it.
The Nissan Scout II was built in June of 1973 as a 1973 model. Like the Perkins Scout, it was ordered as a bare-bones Cabtop for testing, with a 258 six and the T18C 4-speed. This one was ordered with stump-pulling 4.88:1 axle ratios. The paint code was 2289 Flame Red (an orangey red). It was shipped to International’s Melrose park R&D facility for the installation, but not much is known about it’s time there. It was mostly tested in Fort Wayne.
You will notice it has a full length Travel Top on it like the Perkins Scout. That was added at the test facility along with a nicer pair of seats to replace the bench seat. The stereo was also added for testing. Say what? A good deal of the road testing was done on the Fort Wayne test track. Imagine spending 8-plus hours a day going round and round a test track without a radio to keep you at least semi-sane. It isn’t clear how many test miles were put on it, but the odo shows a but over 77K on it now and it’s though to be original and accurate.
In case you didn’t know, the CN6-33 was chosen for the Scout and production began in late ‘75 for the ‘76 model year. We have found evidence of many other Nissan powered test Scouts and it’s known Alan Schaeffer ended up with several of them, along with a pile of engines that were dyno tested.