Build Your First Performance Engine - Part 1: Block Prep And Math

This is pretty standard stuff. The rod is a 5.7-inch H-beam with ARP rod bolts that we have wailed on in other mules without issues.

We are going to use Speed-Pro pistons from Federal-Mogul. The rule here is to get the lightest forged piston your budget will allow. Paying a little more for the floating 0.927 wristpin eliminates the need to heat up the rod or cold-press the pin and risk damaging the piston.

Here is a close-up of the hammered rod-bearing surface on the 400 crank. Avoid this by changing your oil.

The inside micrometer told us the bore taper in the area of highest wear right under the cylinder ridge. It needed to be at least 0.015-inch smaller than the bore size.

The crank was actually a little more wasted than we had hoped. In this case JMS offered us a crank it had on the shelf that was turned 0.010 on the rods and 0.020 on the mains and took our crank to turn later and replace the inventory.

The main bearing saddles were checked for variances before the engine was align-bored. All other machining and measurements rely on the mains being aligned.

The deck of the block will develop waves that will cause the head gasket to fail if they get over 0.010. For a standard rebuild, the machine shop will clean the deck and get it flat and parallel with the crank centerline. We told Sal at JMS to deck the block to 9.005 to get our quench area to 0.043 (0.005 piston deck-height + 0.038 compressed head-gasket height).

Robert Hendrix at JMS recommended replacing the small freeze plugs in the oil galley with a threaded plug to withstand sustained high rpm and oil pressure. You can use a 14-inch NPT tap, just be sure not to thread the hole too deep and block the oil passage between the galleys.

The machine shop you use should apply head-bolt torque to the block when it is being bored. Since the procedure is about the torque on the bolt not the torque plate itself, JMS came up with torque bushings that simulate the stress head bolts put on the block. If you don't do this, the cylinder will distort and the rings will wear causing a shiny spot to appear on the cylinder wall near the bolt location. This is especially troublesome on the 400, where the bolt hole is so close to the cylinder wall.

In part two of the series, we are going to assemble the prepped short-block. The wall thickness rule of thumb is 0.0200 to 0.0250 on the major thrust side and 0.100 on the minor thrust side of the block. The major thrust side is the inboard wall on the left and the outboard wall on the right. Now we can assemble the short-block.