[TJ's GMC]

Originally Posted by BobBray

The GMC V-6 family of engines was designed in the late 50's to replace the two series of GMC manufactured straight 6's along with the 'borrowed' Pontiac and Oldsmobile V-8's. The V-6 idea was actually very rational as the majority of truck engines at the time were 6 cylinders. A 60 degree 'V' design was selected for compactness, 120 degree firing intervals, and a short strong crankshaft. The engines were very 'oversquare' (large bore, short stroke) to provide flat torque curves and low piston speeds. Most every other feature of these engines was designed for maximum durability, like oversized water and oil pumps, large bearings, and high quality materials. For very large trucks and fire apparatus, the basic design could be stretched into a V-12 (later a V-8 as well). It would seem that the design was intended from the start to be made in a diesel version as well.

No question the GMC V-6 was far more durable than any contemporary passenger car/light truck engine, but I think it is interesting to compare the V-6 to contemporary medium/heavy truck gasoline engines. Again, the GMC proved superior to engines like the International Red Diamond and V-401/478/549, the Ford Super Duty 401/477/534, and the REO (later White) V-8's. The GMC's matched or beat those other engines in output but were more durable, lighter (I know, hard to believe!), more compact, and delivered better fuel economy.

WOW! Thanks the sharing! Has anyone dynoed these that you know of? I'd be interested in seeing the torque curve. A friend of mine said the main bearings on these were as big as a 7.3 diesel engine's main bearings. I know GM made the toro flow but from what I've been reading it wasn't a very good success? There is one for sale about 45 minutes from me for $500. Supposedly runs to. Wow...a GM V6 being lighter than something is surprising. lol Thanks.