363ci Stroker Build - Over-Achiever
|w/650 Demon||w/850 Demon||Difference
From a business that literally began in a two-car garage, Dart Machinery has come a long, long way in thirty years, yet has remained loyal to its Detroit-area roots. Like many in the automotive aftermarket, Dart founder Richard Maskin is a racer and mechanical wizard who began engineering and building hardware for his own drag race programs.
Other racers soon took notice of his on-track success, the orders started piling in, and Dart Machinery evolved into a Motor City success story that now spans two huge facilities encompassing the company’s R&D, administrative, warehousing, and ultra-modern machining operations. For the enthusiast, engine blocks and cylinder heads—and now assembled short-blocks—are the primary focus, but we wouldn’t be surprised to see Dart branching out into other components and products as time goes by.
Speaking of cranks, the stroke...
Speaking of cranks, the stroke is 3.400 inches (same as a typical 347’s), and Dart offers the choice of either cast or forged 4340 steel—both sourced from Eagle (www.eaglerod.com)—in its 363ci short-block. Given the high-revving nature of our test engine, we opted for the forged unit.
Likewise, you can choose between...
Likewise, you can choose between H-beam or I-beam (Eagle 5.400-inch) steel rods when ordering your own 363 short-block. Both use ARP (www.arp-bolts.com) 8740 fasteners. Again, given the 7,000-rpm powerband of our combo, we went with the somewhat pricier and theoretically stronger H-beams.
Desired compression will dictate...
Desired compression will dictate your choice of flat-top or (16cc) dished pistons. Both are premium phosphate-coated, high-silicone, low-expansion forged units from Mahle (www.us.mahle.com) with the company’s Grafal skirt coatings. Our test engine uses the flat-top variant (PN SBF090030F06).
After a couple pulls, Jeff...
After a couple pulls, Jeff Lake verified that lash was adjusted within the cam manufacturer’s 0.0018 to 0.0020-inch specs. That plus a little experimenting with spark timing and an eventual carb swap was the grand sum of dyno-tinkering necessary to achieve some striking power output.
As with our earlier 427 project,...
As with our earlier 427 project, we’re topping this 363 short-block testbed engine with Dart’s Pro1 CNC heads, but this time using 210cc intake port variants instead of the 225cc versions. Our dyno results should resoundingly demonstrate the efficacy of these precision-machined 355-T61 castings, with their 2.05/1.60 valves.
The heart-shaped chambers...
The heart-shaped chambers are normally whittled out to 62 cc, but since Dart does all machining in-house, the staff will work with customers on special requests. Dart engine builders Jeff Lake and Tony McAfee wanted to put a little extra compression into our 363ci tester, so they had the CNC operators program 57cc chambers for our pair of heads. With our flat-top pistons, gasket specs, and so on, this calculated to 10.9:1 static compression, yet the dyno pulls were still run on 93-octane pump gas—an impressive feat.
Soon the build got underway...
Soon the build got underway using Dart’s newly introduced high-performance assembly lube. The short-deck SHP block uses standard 302-sized 2.249-inch main journals and Clevite H-series tri-metal bearings engineered for high-revving applications.
With high rpm on the horizon,...
With high rpm on the horizon, Comp Cams (www.compcams.com) Ultra Pro Magnum roller rockers (1.6:1) came onboard, eyeballed here by Tony McAfee who is verifying correct (7.1-inch) pushrod length.
Which brings us to the all-important...
Which brings us to the all-important choice of bumpsticks. With the idea being to get a bit racy with our overall combo, Dart ordered up a solid-roller from Comp Cams. Lobe lift is 0.433/0.431 (for a gross lift of 0.692/0.689 with 1.6 rockers) and duration (at 0.050 lift) is 263/270, all with relatively narrow 110-degree lobe separation. This would be pretty aggressive in a 302, but remember that the extra displacement takes some of the wildness out of it. A custom grind not found in the catalog, this cam can nonetheless be ordered from Comp Cams (grind number FW 4308F/4143F R110.0). Tony installed it straight up.
Ever seen a CNC-automated...
Ever seen a CNC-automated vertical line-honing mill before? Neither had we until we encountered this giant in the smaller of Dart’s two machining facilities. Investments like this keep the company at the leading edge of accuracy and repeatability.
Flow benches are of course...
Flow benches are of course essential in researching, developing, and verifying cylinder head designs, but Dart goes beyond the typical “dry” systems with its own in-house engineered and built wet-flow bench. As the name suggests, this test bench flows not just air through intake ports under scrutiny, but also a safe liquid—stored in the drums on the right—that exactly mimics the flow qualities of gasoline in suspension, without its explosive tendencies. This wet flow more closely reflects what really goes on under your hood.
Dart doesn’t cast its blocks...
Dart doesn’t cast its blocks or heads—these are poured to the company’s specs by a specialized American foundry—but does ALL machining, from bores and deck surfaces, right down to bolt hole threads, in-house on modern CNC milling stations. So custom-cutting such things as the smaller 57cc chambers used on our project’s heads is a no-brainer.
Tony also used Dart’s two-piece,...
Tony also used Dart’s two-piece, adjustable pushrod guideplates that fit together like puzzle pieces and make proper rocker setup a breeze.
As with the Dart 427 build,...
As with the Dart 427 build, an affordable Professional Products Hurricane single-plane manifold got the call to top the 363 project. Rated by the manufacturer as suitable for the 3,500- to 8,000-rpm range, our chosen cam will certainly put it to good use. The intake was port-matched to Dart’s Pro1 CNC heads.
Also shared with the previous...
Also shared with the previous Dart 427 project are the Kooks headers with their generous primaries (no one seemed to remember exact tube girth) and, at least to start, this 650-cfm Demon carb. Heck, even the valve covers, distributor, and wires were “stolen” off its tall-deck 427 cousin for the 363’s dyno testing. It was time to makesome noise…5.0