The numbers in the 401 rocker valley is 243. The 304,360,390 and 401 AMC engines are all the same block. I replaced the 304 with a 401. Early AMC Cranks. Seller 100% positive. The 390 and 401 are great engines but you will start getting into overheating problems with the stock Jeep radiator. Flexplates and flywheels - though they share the same crank flange - must not be interchanged between 304, 360 and 401 versions. Milodon 16271 Water Pump Mechanical For AMC Jeep 290/304/360/390/401 1973-1979. 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. It made 628 hp @ 6100 RMP on 92 octane gas with 10.4:1 compression. In most cases by replacing the flexplate/flywheel this AMC 427 CID engine will replace that tired AMC 304 or AMC 360 or 401. He sold the Ford block for a lot of money when a bidding war happened on eBay. He identifies the block's casting date by numbers in the rocker valley in the front end of the block. Don't get your hopes up. For example, even with the modifications to more reduce emissions and increase efficiency, AMC's 401 cu in (6.6 L) engine was among the strongest factory-spec engines available in an American car in 1971, with more horsepower than Pontiac's standard 455 cu in (7.5 L) and Chevrolet's 454 cu in (7.4 L) that powered the Corvette. Free shipping. Not all AMC crank flange bores are the same. Customer Bruce Rask supplied the AMC block that was cleaned up and bored to 4.195-inch. AMC 401 stroker to 457 In 2005 We had a 68 AMX & had a 401 short block stroked to 457 by Gene Pearson @ Perfomance Concepts (651) 466-0400. The problem with the block is the deck height. Also the 360 is the most common. Unless your going to drag race I would stick with the 360. The 390 and 401 engines used larger ones than the smaller 304, 327, and 343 mills. This AMC crate Stroker engine by Blue Monkey Performance would be EXCELLENT for that AMX, Javelin, Rebel, Scrambler and etc.It will set you back in the seat and still has good all around power. Numbers are 238 which he translates into February 3, 1978. AMC JEEP : 6.6: 401: V8 : Z - 70-71: block #3198901, crank#3190079, 3196921 head#3196921, 3219993 No crankshaft Centering Ring. He thought the AMC block was in the corner of the shop since the ’70’s. Pretty limited on stock piston sizes but I've chosen to purchase the KB 354 - 9.5:1 compression. AMC I6 (and V8) engines do not share block bolt patterns with any other engine, including all Willys, Kaiser and Chrysler engines. Seller 99.3% positive. We had Glenn & Trvis Knowlton @ Knowltons Thunderheads (763) 784-0687 rework Indy AMC Aluminum heads & Indy intake. My AMC 401 block is at the machine shop and after being checked out it can stay at standard bore which really surprised me, a real premium! $122.21. I've read several posts on engines and oiling and I'm comfortable with that area but I'm not sure my piston choice is the best and would appreciate any advice. Check availability. Still have the 304. Amc Jeep V8 390 401 … RPM Machine Works also handles AMC crankshafts, listing applications for 1972-'93 304 and 360, 1968-'70 390 and two variations for the 401 block; one for 1971 and one for 1972-'78. Fuel Pump Block Off Plate Fits AMC AMX 401 Engines F034. I am the original owner of my 1972 Javelin which came with a 304. This block and some rare Ford block were included with a shop he bought out. I firmly believe that’s what he expects for this AMC block. The braided stainless hose transfers oil to the rear of the block to help maintain pressure to the lifters and cam bearings. The 401 was the biggest, strongest engine that AMC offered. $31.99 + $10.15 shipping.