The Mopar 383 Build
With maturity, short-term goals give way to long-term plans and foresight-at least that's the excuse and rationalization that legitimizes the long and drawn-out history of this Mopar 383 big-block. It was back in the late '80s when the original 383 powerplant was pulled from Musclecar Classics magazine's giveaway Challenger project to make way for a replacement mill. The 383 sat abandoned for several years in a lonely corner of the Hot Rod shop, until then-HOT ROD Editor Jeff Smith determined sufficient time had passed to unceremoniously transfer the tired Mopar to the nearest Dumpster. A reprieve came when then-Feature Editor David Freiburger intervened. The 383 spent the next 12 years in Freiburger's garage, contributing to the impressive collection of potentially useful junk-a hot rodder's foresight at its best.
Freiburger and I have spent endless hours bench-racing what to do with the 383: a big-inch stroker combination; an old-school, tunnel-rammed retro motor; a stock-stroke, high-compression, high-rpm screamer; and so on. When we exhumed the 383 three years ago, we were set on a plan to build a budget high-compression, 7,500-rpm animal, using insanely ported stock iron heads and a good old-fashioned tunnel-ram. The 383 seemed naturally inclined for such an approach with the short 3.375-inch stroke, a relatively large 4.25-inch bore, and a rich history of withstanding abuse during the heyday of '60s muscle.
We would enhance the bore by going straight to 0.060-inch-over, and appease our budget yearnings with the stock forged crank and rods-after all, these factory parts were good enough for Super Stock racers back in the day. For compression we'd need domed pistons, which for a 383 Mopar means custom slugs. We ordered a set from Diamond Racing Pistons, but in doing so fell to the temptations of the custom-piston order sheet. With a literal blank page before us, how could we resist the sultry pleasure of a pair of 0.043-inch compression rings and 3mm oil rings? Of course, at that point lateral gas ports also became a must-have option. So our 11.6cc net dome Diamond pistons were not exactly cheap, but that was ever so easy to rationalize given our high-rpm aspirations and the necessity of custom pistons. After all, the standby L2315F Speed-Pro pistons have ancient-tech 51/464-inch rings, and at best, those flat-tops are good for 9.25:1 compression.
No ordinary machine shop would do for the 383; we needed top-quality work and the personal attention this odd build would require. Beyond the cylinder-bore prep, the stock rods would require resizing with fastidious attention to center-to-center length in order to allow an exact zero-deck machining of the block. Vic Moore and Dave Massey at Precision Speed & Machine had us covered, boring the block, reworking the OEM rods with new ARP bolts, installing the pistons using a press-fit at the pin, and carefully mocking up the assembly and milling the decks for a consistent zero-piston-deck reading. Precision also balanced the stock crank for the 720-gram pistons.
Meanwhile, Freiburger began scouring for a suitable low-deck Mopar tunnel-ram. With online sources such as eBay Motors opening a window to a world of potentially useful junk, the search turned up the needed tunnel-ram and so much more. Mining online sources and local swap meets, Freiburger created a personal subculture dedicated to the accumulation of every low-deck Mopar intake past and present. With that, we had everything required to build our vision of a 383 Mopar except those "insanely ported" OEM iron heads. It would prove to be a roadblock that stalled the 383 project for 18 months, with the only benefit being more time for Freiburger's obsessive pursuit of manifolds. As the stockpile grew, so did the ambition: This would serve as the basis of the most comprehensive low-deck Mopar intake comparison of all time. That ambition redefined the 383 project and ultimately led to its completion.
It became a familiar exchange, "How's my 383?" Freiburger would ask, to which I'd reply, "We need heads." "You can't get them done?" "No." No matter how much I wanted to, I just couldn't find the room to block out the 40-plus hours to machine, weld, and hog out an old set of iron heads. So the 383 parts sat and the manifolds stacked up. Nearly two and a half years into the 383, with the introduction of Edelbrock's new Victor heads for the Mopar big-block Wedge, a new master plan was hatched.
Two versions of the 383 were required, one moderate and one wild, with heads, cam, and compression creating the distinction. Version A would utilize nothing more than a stock OEM set of No. 906 factory heads with no porting and stock valves. The factory 88cc chambers would yield a compression ratio of 10.3:1, while a fast-ramp Comp Cams MM-series flat-tappet solid camshaft would pull around 450-470 hp through the stock heads. This would be our base street-type engine. Engine B would receive either a much larger solid flat tappet or a solid roller, and the new Victor heads. The much smaller chamber of the Victors would allow the same pistons to yield a 12.5:1 compression ratio. This would be our high-rpm, high-output strip engine. Naturally, we would expect some manifolds to be more suitable on one of these combinations than the other. With the two versions of the engine we could really sort the stack.
With a new sense of purpose and no longer requiring the ported stock heads, the 383 was finally completed in less than a week. With a mountain of manifolds at the ready, it's as though we intended this conclusion all along-call it foresight. For now, check out how the engine went together, then tune in next month as we wave a bunch of intakes across it and see what it's all worth.
See The Power Next Month!
Come back for more as we do back-to-back cam testing and try a truckload of swap-meet intakes on our basic 383 Mopar.

Photo Gallery: The Mopar 383 - Engine Buildup - Hot Rod Magazine



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