We brought our block to Jim...
We brought our block to Jim Grubbs Motorsports because quality machining pays dividends on the dyno, and it was power we were after. Jim cleaned the block, and then bored and honed it to inside .0001-inch with torque plates in place. That's precision.
What's not to like about the 383? It seems these engines have recently fallen out of favor as attention has turned to big-blocks of ever-increasing cubic inches. Big inches are good, but it takes equally big heads to get your money's worth out of them. Smaller engines need to make up for their size with speed, and speed here means rpm. In this regard, the 383 truly fits the bill. A good "rev motor" has a big bore to make room for large valves, and a short stroke to keep piston speeds down and rod ratios up. Take a head from a 440, and that 383 at 15 percent smaller will give you roughly 15 percent more useable rpms. So, a 5,500-rpm combo in the bigger engine will turn into a 6,300-rpm combo in the 383. Though it won't make the same lower rpm torque, the outright peak power number will be surprisingly close. For a moderate investment, a good 383 can be built into a high-revving powerhouse; Chrysler's most common performance big-block has a bore/stroke the other guys would kill for.
Torque plates really do make...
Torque plates really do make a difference. Jim lightly honed a bore, and then pulled the Sunnen hone head out of the bore. The distortion created by the head bolt load was clearly visible in the bore. The bores pulled out .001-inch under the bolt locations, or .0005-inch per side, visible as the dark area here where the hone skipped over the depressed area. Once honed out to final size, the bore will be perfectly round with the heads bolted on.
Study the 383's numbers compared to the popular engines of the competition. The 383 carries a bore and stroke of 4.25-inch x 3.375-inch, while the 396 Rat had an embarrassingly undersized bore of 4.094-inch, and a 3.766-inch stroke-as long an arm as a 440. At the Ford camp, the 390 was even worse, with a bore only slightly bigger than a 340 at 4.050-inch, and again a 440ish stroke length of 3.780-inch. The 383 was a thoroughbred by comparison to the competition's similarly sized big-blocks. In fact, the FE Ford fan's coveted 427 block had less bore diameter than the dirt-common Mopar 383. Even the Chevy guys' big guns, the 427 rat and the 454, had bores no bigger than Chrysler's 383. You won't see Ford or Chevy fans passing up 427 FEs or 427 and 454 Rats, but we tend to walk by those 383 Furys with nary a second look. Despite the shadow of the 440, the 383 is a great engine.
We decided to explore the B-Magnum's hidden potential. Anyone who remembers the 383-equipped musclecars knows that these engines can run. Garden variety 383 Road Runners, Super Bees, Challengers, 'Cudas and A-Bodies vastly outnumbered the more exotic Hemi and Six Pack cars back in that era, and these 383 cars contributed far more to the musclecar mystique and legend than they are given credit for today. We decided to put a 383 together to blueprint-stock specs to see just how much power a stock 383 put out. In the day, the 383 was one of the most modified engines ever installed in performance cars, responding eagerly to basic bolt-on speed equipment. To tap into that potential, next month we'll baseline the stock engine on the dyno, and then use some of today's best performance hardware, taking our 383 from resto-stock to racy-rad.
Jim lightly honed the lifter...
Jim lightly honed the lifter bores to remove burrs that could hang up a lifter or keep it from rotating, which could cause cam or lifter failure.
The block was squared and...
The block was squared and zero-decked. Doing this accurately required precision fixtures, such as this BHJ apparatus that Grubbs used.
After Grubbs finished, our...
After Grubbs finished, our machined block was taken home, where the bolt holes were chased with bottoming taps and scrubbed-out and cleaned, a new distributor bushing installed, and new gallery and freeze plugs put into place. The block was then masked and painted with PPG Hemi Orange urethane. With the prepped block and our stash of balanced internals from PAW, we were ready to build. We installed the cam bearings ourselves, using a cam bearing tool kit from Powerhouse. It's a simple job, and the tool kit more than paid for itself with the number of times we've used it.
With the upper half of the...
With the upper half of the rear seal in place, the PAW-supplied forged 383 crank was laid on the Clevite bearings from our kit. We checked crank runout, and it was dead straight.
A Plastigauge check showed...
A Plastigauge check showed just under .002-inch clearance in the mains. We reused the stock maincap bolts.
Crank endplay measured within...
Crank endplay measured within specs at .007-inch, so all was well with our balanced PAW crank.
The piston skirts, pins, and...
The piston skirts, pins, and cylinder bores were lubed with motor oil, and the pistons were knocked into the bores. The asymmetrical valve notches of the pistons mean they must go into the correct bore. Confirm that the large chamfer on the cheek of the rod big-end goes to the outside of the journal, and that the valve reliefs match the valve order of the heads.
We checked the rod bearing...
We checked the rod bearing clearance with Plastigauge, and again found just under .002-inch. The chrome-moly PAW rod bolts were torqued to 60 lb-ft with oil on the threads.
We had PAW fit the KB pistons...
We had PAW fit the KB pistons to the reconditioned stock rods. The supplied Hastings moly rings were pre-gapped, so we just had to wind the rings in place, insert the bearing shells, and the reciprocating parts were ready to install.