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AMC 360 Engine Build - 370-Inch 480HP AMC

Got an AMC? Why build a hard-to-find 390 or 401 when the 360 grows on Jeeps? Follow along as we build a 370-Inch 480HP AMC

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It was nearly a year ago that we got the jones to build an AMC. After checking prices on the most popular AMX and '70 Javelin bodies, we found them priced out of our budget just like every other desirable musclecar from that era. Our solution was simple: the Rambler American. We found 290 V-8 cars for around $1,000 in hammered shape and some in minty-fresh factory condition with six-cylinder/auto running gear for about twice that. We scored a '67 with a 232 and a two-speed for $2,000. Our big plan was to swap in a 390 or 401 for a little street-machine fun. That was before we found out that a broken-core block was $200 and running engines were clearing a grand.

We found a fast solution for that too when the Jeep guys divulged the secret of the AMC 360. No, it's not a Mopar engine, it's all American Motors with a 4.08 bore and 3.44-inch stroke destined for the big-body Javelin, 360 Hornet, and a healthy mix of Wagoneers and other vehicles with a production run from 1970 to 1991 (or 1992 depending on who you ask). We took a trip to Pick Your Part in Sun Valley, California, to have a look for one. We found five 360s in various states of disassembly, so we got to pick and choose. We selected an '85 Jeep Grand Cherokee because someone had already pulled the hood, radiator, and most of the useless junk out of the way. We swooped on it and pulled it in about an hour. Total price for the short-block? $89.

The 360 uses cast internals and has a couple of hereditary oiling problems that need to be dealt with before you can make good power. There are forged rods with pistons available for the 360, but they usually represent part of a rotating-assembly combo that gives you around 9.0:1 compression with 53 cc. We wanted at least 10.5:1 so we could have decent snort and use gas from the pump. For this we opted to use Chevy 6-inch small-journal rods and custom pistons from Lunati. The price for the combo is roughly the same as other aftermarket AMC assemblies, because the low price of the rods offset the expensive pistons whereas other AMC rotators are 50/50. Just plan to spend $1,000 and pick your compression ratio.

Finally we used all the common bolt-on parts from Edelbrock that are available ready to install off the shelf.

We took the parts to JMS Racing Engines in Monrovia, California, to assemble and dyno-test four different combos that represent what the average street-machine guy would build using new bolt-on parts from Edelbrock then pushed it to the level of the weekend racer with a larger cam, intake, and big tube headers to see what it could do. Check it out.

Short-Block Assembly
The biggest hurdle in assembling the short-block is the oiling system. The stock path for AMC engines is from a pickup in the sump, through the block via an oil galley then into the oil pump, then eventually to the mains, starving the No. 4 and 5 main bearings at high rpm. We used a Milodon deep sump that is designed to accept an external pickup and feeds the oil pump directly with a braided-steel line that bolts between the stock oil-pump body and oil-filter-adapter body. This, in combination with an AN -6 line from the main oil galley to the rear of the lifter valley, gave us 80 psi of oil pressure at 6,000 rpm.

Otherwise we used the stock crank offset ground to accept the 2.00 big end of a Scat 6-inch Chevy-style rod. Since the stock rod is wider than the Scat I-beams, to use them, AMC guys must weld the crank filet or the big end of the rod to get them to fit. That and the custom Lunati piston gave us a zero deck after cleaning up the head 0.010 to 9.198.

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