The 401 cranks and rods are forged and tough enough for a performance rebuild. Look for the 5.858-inch rods and the forging mark (left) on the crank. Builders have also been turning down the rod journals and using new 2.100 Chevy rods for performance 401s.
Transmissions
Early AMCs came equipped with the Borg-Warner Shift Command automatic or the T10 four-speed on the performance models. The T10 has always been a decent piece, but the Shift Command automatic shifts poorly and has little or no aftermarket support for performance use. The reason is that after 1972 you could get the TorqueFlite 727 Chrysler transmission with an AMC bolt pattern from a fullsize Jeep or AMC passenger car. With the door open to all the mainstream Chrysler speed goodies like converters, shift kits, and shifters, it's no wonder the early automatic is more for pleasant street cruising while the 727 is used for Friday night drag racing.
The easy way, of course, would be to pick up a catalog and order the 727 or even a 904, a converter, and a shifter and call it done. But if you're into it, Advance Adapters has an adapter to retrofit any GM trans, including overdrives.
This is a stone-stock 401 from a '78 Cherokee. If you know what you're looking for, it isn't too difficult to score in the boneyard. The engine builders we spoke to told us building 450 hp at 6,500 rpm is no problem if you modify the oiling system to supply the No. 4 and 5 main bearings.
The standard transmission is a bit more straightforward; if you're lucky enough to score a four-speed T10 car, leave it in there. It also should be known that the T5 five-speed from late-model Mustangs and Camaros can be used with the stock bellhousing from the 401 AMC V-8. With a pilot bushing or flywheel swap, both are acceptable for performance applications.
Details
Finally, the dress-up. Unlike Big Three cars, AMC used the 5-on-4.5 bolt pattern on all its musclecar-era cars. This happens to be the same bolt pattern as Ford and Chrysler, so swap meets and any of the huge number of wheel makers can provide rims for an AMC. Also, because of the Jeep guys, you can score about any part for the engine in chrome. All good, just don't overdo it. CC
After 1970, the 390/401 engines had dog-leg exhaust ports. Early text suggests they flowed 50 percent better than the rectangular design. This is more for identification since we would probably use modern aluminum heads. | 
Although these engines are from the same family, they share external dimensions only. Left-to-right are the 390ci, 343ci, and 290ci blocks. A few '69 blocks and all '70-'72 blocks have the cubic inches cast on either side near the motor mount. |
This is the Model 20 that you get with a V-8 AMC. It's got a bad reputation, but with the right parts it will work in a healthy street machine. | 
Here is the problem with the Model 20. The axle passes through the hub and is attached with a bolt. Fixes include replacing the hub every time the two are separated, following the complicated factory setup procedure, adding extra Woodruff keys, or replacing the axles with a new one-piece set. We fear all but the last fix. |
The TorqueFlite 727 has an AMC bolt pattern after 1972. These can be rebuilt using the standard Mopar performance goodies. It can be ordered from aftermarket companies as well. They are not rare. | 
Everything you see here is off-the-shelf for the AMC. This 401 has an Edelbrock Air Gap intake and Thunder Series carb, Crane ignition and cam, Comp Cams roller-tip rockers, a high-flow water pump, and ARP bolts. Pretty mainstream for a car company that disappeared in 1987, don't you think? |
Barn Cars
We found several cars hidden in a warehouse right here in Los Angeles. Know what they are? Log on to carcraft.com if you think you do.