Engine Building - V-8 Power Trends And Best-Selling Engine Combos

The next step above the 420ci engine involves some crazy cash and the Indy block.

AMC 401/420
The highest-volume and most common AMC build is the 420 stroker. It uses a 401 block that had been bored to 4.195 and a stock forged 401 crank that has the rod journal turned down to 2.100 for a 3.800 stroke. The rod journal is then widened to 1.900 for a 6-inch forged Eagle I- or H-beam rod with a floating 0.0927-inch wristpin. The pistons are custom Diamond Racing or Venolia that yield anywhere from 10.0-13.0:1 compression, depending on the application.

Most guys are using the No. 291 iron-head casting from '70-'71 with a 50cc chamber or the No. 090/993 casting from '71-'73 rebuilt and ported to flow above 280 cfm at 0.500 lift. The street version with 10.5:1 compression, a Holley 750HP carb, a Torker intake, and a solid-roller cam with 0.640 lift and 251/260 duration at 0.050 makes about 500-550 hp. There also is a more brutal version that has a 4.250 bore and 3.800 stroke and a 13.5:1 compression ratio. With a custom Comp Cams solid roller with 0.747/0.763 lift and 278/288 duration at 0.050, it makes in the neighborhood of 700-725 that everyone agrees is nearing the limit of the stock block. The next step is a 4.250-bore Indy block with a custom 4.150-stroke Moldex crank for 450-plus inches.

If you are a A-body guy, this is the package for you.

Small-Block Mopar 408 Ci
Even though the big-block outsells the small-block 10 to 1 these days, we'd be remiss if we didn't find out what small-block guys were building. We asked Mike Ware at Muscle Motors and the simple answer is the 408. Using the original LA 360 ('67-'85) block bored to 4.030 and an Eagle 4.00-inch steel crank, a 10.0:1 compression stroker can make an easy 500 hp and 525 lb-ft of torque. The stock iron block requires only a small notch at the bottom of the cylinder to clear the connecting-rod cap screw. The stock rods are replaced with a steel H-beam that is 6.123 inches and an off-the-shelf piston from KB or Diamond Racing is used with either a flat-top or dish, depending on the desired compression ratio. Ware also tells us that a hydraulic flat-tappet cam is a cost-effective way to keep prices down and he offers a single-shaft rocker system that works with Edelbrock RPM heads. This is topped with an Edelbrock Performer RPM intake manifold and a Quick Fuel 850 carb. The Mopar A-Body is the target for these engines, so you can also source an oil pan and headers from Muscle Motors and TTI.