When it comes to small-block Mopar power on a budget, the 360 is the undisputed king. As the largest factory small-block, the 360 started life as an underappreciated smog powerplant in 1971, and the same basic configuration saw continuous production for a good three decades. While the 360 was offered in some performance oriented vehicle packages through the ’70s, the engine’s 340-cube little brother from the muscle car era got all the glory as the hot performance piece. However, the 360 had the cubes and the massive OEM production run to make it the logical choice for small-block performance today. Though out of production for about a decade now, by sheer weight of numbers the 360 remains readily available in boneyards across the country.
With today’s aftermarket parts, a 360 can easily be converted to a fire-breathing stroker with well over 400 cubic inches of displacement. While cubes are a sure way to more grunt, the factory 3.58-inch stroke combination remains hugely popular for lower budget builds or engine swaps. We wanted to explore the untapped potential of a basic 360 combination, taking the engine well beyond the typical 400 horsepower range of the basic street performance build. Our plan to get there would be to take the engine’s breathing to the next level, while maintaining a budget approach in keeping with the 360’s working class roots.
01. Our block was an older remanufactured 1977 360, which we found was already bored .040
02. A stock 360 cast iron crankshaft was ground .010/.010-inch under, and we were able to
03. The opportunity to internally balance our 360 was a result of the lightweight Scat 6.
Basic Bottom End
The foundation for our build is a common 1977 360 casting, pulled from a truck. We actually pulled the engine years ago from a junked truck, but the upshot was the block had been previously remanned. While a remanufactured engine is generally built to the lowest cost possible as far as the internal components, we were pleased to find the .040-inch overbored block showed bores that were in excellent condition. Normally an engine build will start with a trip to the machine shop for a bore and hone, decking, and usually line honing the mains. In this case, with our particular block, careful measurement showed that the existing machining was fresh enough to build upon. We just cleaned up the block, hand honed the bores, and called it good enough. The factory cast iron crankshaft was polished at its existing .010/.010-inch undersize, and the essentials were ready to go for next to nothing.
Filling the bores, we detoured from our rock-bottom budget approach, stepping up to a set of Probe forged flat-top pistons, and stock-length Scat I-beam rods. The previous rebuilder’s cast, dished pistons had no place in a performance build, so a piston upgrade was a must do for added durability and increased compression ratio. The Probe pistons offer reliability at an affordable price, representing a good upgrade over the existing pistons. To seal the pistons to the bores, a set of SpeedPro file fit moly rings were selected. Again, there are cheaper alternatives, but the moly rings are well worth the added cost for longevity of the bores and performance. We gapped the rings to .016-inch, top, and went much wider at .030-inch at the second ring.
The strong Scat 4340 forged I-beam rods offer peace of mind, and also provided the advantage of lighter weight than the stockers. These rods come with wristpin bushings, 7⁄16-inch ARP bolts, and all things considered are a sensible upgrade compared to rebuilding the stockers. The lighter rods and pistons enabled us to internally balance the crankshaft, eliminating the need for the stock 360’s weighted damper and flywheel. With this internal parts combination, the factory cast iron crankshaft did not require expensive Mallory metal to achieve the internal balance, getting there by just filling and welding the large factory balance holes in the counterweights. The crankshaft was installed with Clevite bearings at .0024-inch clearance using the factory main caps, secured by Milodon studs, and a zero balance Professional Products damper was hung on the nose.