All Aluminum Versus All Cast Iron Engines

[David D.]

Re: Answer: The Other All Cast Iron GM Engine

Joe, As for as I know, it was, as you say, loosely based on the 62-69 version of the 153 cu in engine. The later revised version, you refer to as the "Iron Duke", that was used in commercial and other applications, was available in 151 (4 inch bore X 3 inch stroke) and 181 cubic inch sizes. The 181 cubic inch size used the same 4 inch bore, with just a slightly longer stroke. I believe the block was the same as the 151 version. I know for a fact, that the 181 cubic inch size engine was used in many of the Sullaire stand alone Q-type Air Compressor's in the early 90's and probably much later. I may still have some spec's on it somewhere. FWIW. Dave

[Duke W.]

Re: I seem to remember....

I don't recall hearing that GM offered to buy the tooling back, but I wouldn't be surprised.

I do specifically remember that Prof. C. F. Taylor, retired manager of the MIT/Sloan Automtotive Labs and author of the two-volume 1400 page "bible" of IC engine design chided Detroit for shoving four cylinder engines down our throats. Prof. Taylor said that smaller V-8 engines could provide equal fuel efficiency, while being much quieter and smoother. Four cylinder engines cost less to manufacture, so there's your answer.

"Iron Duke" and the early Chevy II I-4 that it was derived from shared a lot of archicture and parts with both the SB V-8 and I-6 engines. For example, crankshaft journal sizes are the same as small-bearing SBC/I-6. The rods are the same as the SB except for being a bit wider (1.02") at the bottom end, and this particular rod architecture is common to the I-6 and later Vega engines, and some valvetrain components are shared.

Don't confuse this engine with Pontiac's four-cylinder engine of the same era that was used in the Tempest. Now that engine was effectively half a Pontiac V-8 including the cylinders inclined at 45 degrees, and I think it used the same head as the V-8. It was a rough, noisy engine due to the large bore and stroke, and it didn't last long. Other than the block, crankshaft, and camshaft essentially all the other internal parts were straight from Pontiac's V-8.

Pontiac only had one V-8 architecture. The intial 1955 version was 370 CID as I recall, and it was ultimately developed to 455 CID before it was dropped when GM went to "corporate engines".

Duke