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 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.
The Build
Our goal this month is to bolt together a stock-spec 383, built to match the 383 Magnum engines of yesterday. Thirty years after the last ones came out of Chrysler's engine plants, 383 cores are still amazingly common and cheap. We traded Hot Rod editor David Freiburger a virgin 440 steel crank for a complete 383 Magnum core. The 383 crank was already ground down to the minimum, and the block was already .030-inch-over, but we can't blame David since we picked this block from one of his several 383 cores. Taking the block out to .060-inch-over didn't have us worried, but we were still left with finding another crank. We tapped into PAW's extensive catalog for their Super Stock master kit, which includes a crankshaft, rods, pistons, rings, bearings, gaskets, oil pump, timing set, cam, and lifters-basically everything we would need to make our 383 as good as new.
Our MP PN P4452783 Resto cam is exactly the grind used in the factory 383 Magnum engine. Specs are 268/284 gross rated duration, .450/.458-inch lift, with 46 degrees of overlap, and lobe separation of 115 degrees.
We made a few upgrades to the base kit, including custom balancing, moly rings, chrome moly rod bolts, and a high-volume oil pump. These low-cost options on the PAW kit were well worth the price for the sake of performance and reliability. Also on our list of upgrades was a set of Keith Black KB-162 Hypereutectic OE replacement pistons. These pistons are designed to give approximately the stock compression ratio, but have generous valve notches allowing us to move to a fairly aggressive camshaft later on. For the baseline, a resto-spec Mopar Performance "Road Runner" cam and lifter package were specified as an extra cost option, since we were looking to duplicate a factory 383 Magnum for our initial configuration. We were also short an oil pan, so a PAW unpainted steel replacement sump was ordered, along with a dipstick and tube kit. Even though we were starting with little more than the original block, the PAW kit made building a balanced and blueprinted 383 bottom-end surprisingly affordable, and very easy.
We used a PAW brand double roller chain kit to drive the cam. MP recommend an installed centerline of 113 degrees, which checked out with no mods required. Offset bushings are available for the cam gear if cam timing adjustments are required.
Since PAW handled all the internals, all we had to contend with was the block machining. We didn't want to skimp on cylinder bore prep, so we went to one of the best regional shops, Jim Grubbs Motorsports, in Valencia, California. Jim handled the block machining on our 408 small-block stroker, and we were very impressed with the quality of the machine work and eventual output of that project. Jim first cleaned up our 383, then bored the block and honed it with torque plates to fanatical precision. The block was decked square to the crank centerline using a BHJ indexing fixture on Grubbs' Rottler mill. A cut of .010-inch on our previously machined block gave us a zero deck height with our KB Hypereutectic pistons. That's all the machining we needed for this project. We already had a set of fresh 906 cylinder heads, rebuilt to stock specs with the original 2.08/1.74-inch valves, which we had previously rebuilt ourselves with new guides and a Serdi valve job.
Using the PAW kit and Grubbs-machined block, we had all the components ready to put together our 383 in a remarkably short amount of time. Since this was to be a basic stock rebuild, the actual assembly was very quick, simple, and trouble-free. Unlike building a custom race engine, this kind of stock buildup goes together without massaging components typically required in building a radical custom racing combination. The 383 was a piece of cake to put together, but we suspect the final output will rival some more exotic small-block combinations. We'll see next month if our hunch is valid.
