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I was invited to a big bash in the next village- about nine miles away and over the border in Colorado. i have been driving my 1 1/2 ton on local errands to give it some exercise. Being that it was the 4th I drove it the 9 miles over our dirt roads and two lane blacktop. It was a sunny watm day so I had the windshield all the way up. I keep the speed around 30 MPH or so. I am guessing becuase the speedo spins, likely a cable? It was great cruising. I am getting the down shifts from 4th to 3rd down good and even had a few slow 3rd into 2nds that went off without a grind. These trucks sure a pleasure to drive!

So, I eventually got around to me favorite daydream- engine replacement. This 235 already has been punched .060 over. It runs fine, burns little oil, at our altitude (7,800 to 9.,000 feet) it huffs and puff some. Does anyone remember the 305 or 351 CI V-6 (designated 6066?) GMC put in their light duty and some medium duty trucks in the 1960s? What kind of reputation did than engine have? The larger displacement and shorter block seem appealing. Has anyone had experience with this engine? I was too you when they were commonly in use although I remember seeing them on all kind of truck in construction, forestry and agriculture use. I am wondering if this might be a good replacement engine candidate.

Hi Untergruppenfuher,

Are you up in N. New Mexico, close to Alamosa or Pagosa Springs? For a quick test of your downshifting skill, try Wolf Creek Pass.

No really...sounds like you had a great 4th.

As for your engine swap...you just missed Ranger. I'm sure he would of given you some advice.

Has to be a GMC 270

My 1.5 ton had a 270 in it, mated to the original Chevrolet transmission. No idea how it was done, never had it apart, but it moved very well and was relatively quite - didn't need the fifth ovedrive that the original transmission would give.

The 270 was the OEM engine for the 6X6 2.5 tons trucks, right? THey must be scarce to find. If I went I6 my choice would the 292, even though it means moving the radiator out some. I love that engine- torque peak at 1800 RPM, power to spare. I just thought the 301 cubic inch V-6 would have a shorter block (front to back) and fit more easily into the engine compartment while still having some great torque specs.

Vista52 wrote:Hi Untergruppenfuher,

Are you up in N. New Mexico, close to Alamosa or Pagosa Springs? For a quick test of your downshifting skill, try Wolf Creek Pass.

No really...sounds like you had a great 4th.

As for your engine swap...you just missed Ranger. I'm sure he would of given you some advice.

Never been up Wolk Creek Pass but been over La Veta pass on both the old and new roads many times. Not in this truck, I have not. If I were to try it in this truck I might try and coast down the Walsenberg side- that long straight grade. Coming back up is likely 3rd and down to 2nd. Overheating would be likely with the 235 "splash" oil system. That leads me to my next question which I will post seperately.

Untergruppenfuher wrote:
Coming back up is likely 3rd and down to 2nd. Overheating would be likely with the 235 "splash" oil system. That leads me to my next question which I will post seperately.

This is the exact operating circumstances that the military had in mind for the 1 1/2 ton ,the cooling sytem ( if properly maintained ) is much larger than any civi application of the time.

In 1943 there were several 1 1/2 tons in the desert of North Africa and they served well .....until being replaced by CCKWs in Italy ( the reason for replacement was not dependability ,but that the 9 foot cargo body was to small.

B

Any V engine would be a difficult swap, interferance with the steering colume/ exhasut manfold. stay with a inline best bet.

Untergruppenfuher wrote:The 270 was the OEM engine for the 6X6 2.5 tons trucks, right? THey must be scarce to find. If I went I6 my choice would the 292, even though it means moving the radiator out some. I love that engine- torque peak at 1800 RPM, power to spare. I just thought the 301 cubic inch V-6 would have a shorter block (front to back) and fit more easily into the engine compartment while still having some great torque specs.

Well the thing about the 270 is that it is rock solid reliable, same external size, and will drop right in with minimum modifications and look right. Only thing I'm not sure about is how to mate it to the Chevrolet transmission.

Conn wrote:Any V engine would be a difficult swap, interferance with the steering colume/ exhasut manfold. stay with a inline best bet.

Sounds like good advice. There is not an abundance of space under that hood. There sure a lot of Chevy and GMC I6s out there.