AMC is one of those companies that artfully misses most of the “gearhead months” around here at BangShift because their engine displacements don’t fit. 343? No. 390? Not so much. 304? Got that one and today we have the big daddy of the lineup the AMC 401 V8. This engine came in on the ragged tail of the muscle car era (AMC was always a little late with anything good) and carried a rating a 330hp for that one shining year in 1971. After that the horsepower numbers dropped like rocks as they did everywhere else but the tough as nails engine trooped on all the way until 1978. You could option a 401 V8 in cars up until 1975 and in trucks until 1978.
The engine has a 4.165″ bore and 3.68″ stroke as produced and the engines for the first several years got forged crankshafts and connecting rods. Interestingly, there was never a 2bbl version of this engine offered. They were all equipped with four barrel carbs through the years. Again, mirroring all engines of the time, declining compression ratios ankled power numbers. The 1972-1975 engines were rated at 255hp and used an 8.5:1 squeeze ratio inside the engine.
Interestingly, AMC made the swap to use Chrysler Torqueflite transmissions after 1972 so the cranks are slightly different to accommodate that change. The only other real difference inside the engine with the 401 as opposed to other engines in the lineup were the diameter of the bearing journals. The 390 and 401 engines used larger ones than the smaller 304, 327, and 343 mills.
The 401 was the biggest, strongest engine that AMC offered. While its brute strength was only on display from the factory for one year, its reliability and toughness lasted nearly all the way to the end of the decade.
A former boss of mine had either a ’73, or ’74 International 1/2 ton pick up. From the factory it had an AMC 401. It was a 2BBL. I used it for a summer to pull my 396 Impala to the drags. 20′ steel trailer, and it was “Pick your opening on the freeway, an drive it in there”. Plenty of power!