Muscle Mustangs & Fast Fords
Dart SHP Sport-Block Engine Build
We Combine A Dart SHP Short-Block And Top-End Kit To Produce 476 Hp Without Breaking The Bank.
Tony McAfee and Jeff Lake assembled our engine and performed the dyno testing with Dart's in-house engine dyno. Over the course of two days, the engine was built and tested, along with a few carburetors and two sets of headers. Our initial dyno pulls were made with a Barry Grant Demon 650 carburetor and a pair of Kooks dyno headers. The fuel utilized in all dyno testing was a high-octane ERC fuel. We didn't run this engine on pump gas because Dart uses the dyno for Pro Stock engine testing and the team prefers to keep fuel changes to a minimum so the system doesn't get contaminated.
McAfee and Lake found that 30 degrees of timing was optimal; they tried a bit more and a bit less, which resulted in losses in horsepower. Dart claims this combination should make around 475 hp, and we almost hit that mark on the first run with the engine making a peak of 468 hp at 5,900 rpm. The promotional literature shows 475 hp with a 750-cfm carburetor, but we wanted to see how far we could push the 650 carb. The team grabbed a wooden 1-inch spacer and installed it--power increased to 476 hp and peak rpm was raised to 6,000.
Dyno testing is fun--it's very easy to make changes, and we had a Demon 750 carb waiting in the wings. McAfee and Lake felt the spacer is required for this combo, so it was left on when the 750 carb made its way on to our 363. Lake was quick to comment during the carb swap, "Bigger isn't always better." He was right: The peak dropped to 465 hp, but as McAfee pointed out, "We picked up 10 hp in some areas around 5,500-6,500 and had 8 more average horsepower through the entire pull." The guys swapped to a set of smaller headers (from 2-inch to 1 7/8) and the power dropped off. The Kooks headers were the hot ticket with larger primary tubes and 3-inch collectors.
"I would run the 650 over the 750," commented Lake. "The 650 is a little more driveable than the 750 as you tip into the secondaries. You aren't going to see or feel the small difference in average power, but the 650 would be a better carburetor for this combination on the street." At this point, Maskin was watching over the dyno runs and said, "This engine will make that power all day long and last over 100,000 miles on the street."
McAfee and Lake also threw in a few comments about fuel injection. "We just played with a small-block Chevy with the Motorvation fuel injection, and it picked up a little bit over the carburetor," said Lake. They were quick to say that adding fuel injection shouldn't hurt power, and in some cases, it might pick it up. The testing on the Chevy was accomplished with a carbureted intake converted to fuel injection and a carburetor-looking throttle body. It picked up average horsepower and didn't hurt the peak numbers.
We were trying to keep tally of the parts needed to complete the Dart short-block and top-end. For those who are buying it all new, save some budget money for the valvetrain (cam, lifters, pushrods, and rocker arms), carburetor, 28-ounce balancer, timing chain and cover, distributor, spark plug wires, water neck, water pump, and oil pan and pump. If you want a reliable and reasonably priced 363ci or 347ci that makes upwards of 476 hp, just order it from Dart or one of its dealers (listed online). Soon the company will offer CNC ported heads, and with that combo, the 363 could eclipse 500 hp.
The Dart 363ci could power a street/strip 3,200-pound Mustang to high 10-second times with ease. That is without a power adder and with street amenities like A/C and heat. Now if you add the H-beam rods and a forged crankshaft, a little hit of nitrous could carry your Mustang into the 9-second zone.