Modified Mustangs & FordsHow To Engine
Ford 302 Small-Block: 400 hp On Pump Gas!
Affordable Power--Would You Believe for Under $2,500?
Standard Ford 289 and 302 small-blocks were factory-rated between 200 and 230 hp. The vaunted 289 High-Performance engine was said to make 271 hp. Today, if a 302 Ford makes 360 hp on pump gas with a hydraulic cam, most experts consider it to be a pretty good motor-at least until Joe Sherman steps up to the plate. Sherman made his reputation coaxing ungodly amounts of power from Bow Tie powerplants for a reasonable price; recently he applied his magic to the little Fords with astounding results.
Forget about 360 hp. How about 400 hp-with ported stock heads, a cam with only 280 degrees of advertised duration, and one four-barrel carb? Better yet, Sherman says you can build an engine like the one on these pages for around $2,500. This price assumes you do most of the work yourself, farming out only the necessary machine work and cylinder-head porting; figure $3,500$4,000 if you farm out everything.
The key to keeping costs down is to spend time and money only on necessary parts, avoiding glamour items, then shop around for parts deals-just like Sherman does. You don't need forged pistons, trick connecting rods, or fancy extruded roller rocker arms. What you do need is sound machining; a good set of cylinder heads; the right cam, intake, and exhaust; and meticulous assembly techniques. Read on to find out what it takes to make your 289/302 First On Race Day.
The bottom end only needs to be strong enough to live at the desired power level-in this case, 400 hp. Stay away from the fancy stuff and spend your money on the top end. If you have a 289, Sherman says a 302 crank's 0.130-inch-longer stroke is worth at least 15 lb-ft of torque.
Because 289 cranks and rods are getting rare while 302 components are as common as sand on a beach, a local crank grinder should be more than happy to trade 289 stuff for 302 parts.
Forged pistons aren't needed. Although Sherman has used standard cast "rebuilder specials" in the past, the engine in this article features Federal-Mogul's Speed-Pro hypereutectic pistons with pressed pins supplied by Powerhouse Engine Components. Although the Speed-Pro units cost about $40 more than standard castings, they also produce reasonable deck heights. In contrast, typical standard rebuilder piston decks are as much as 0.020 inch lower than stock, leading to low compression and a loss of quench. When installed to design blueprint specs, the Speed-Pro pistons end up 0.011 inch down in the hole. However, to achieve the desired 9.54:1 compression ratio, Sherman had the block's deck milled lower than the production 8.206-inch crank-to-deck dimension to yield a final 0.005-inch piston deck height.
The pinholes on Federal-Mogul and other replacement pistons are offset 0.060 inch from center to maintain quiet operation in stock applications. Normally the piston is installed with the notch facing forward (the pin and rod are offset toward the front). Installing the piston backward (with the pin and rod offset toward the rear) reduces rod angularity; the engine behaves as if it has a 0.300-inch-longer rod.
Hastings supplied the piston rings, which included a moly top, a cast-iron second, and standard-tension oil rings. To achieve quicker break-in, the pistons are installed with 0.001 inch extra skirt clearance. Engine Supply machined and balanced the engines, then machined the cylinder heads. There's no need to modify the oil system; just install a new stock replacement standard-volume oil pump.
For this article, Sherman tested the 306.1ci engine using an Edelbrock Performer 750-cfm square-bore carb, a 3-inch spacer-plate, and both Performer RPM dual-plane and Victor Jr. single-plane intake manifolds. Sherman reports that the spacer helps the top-end numbers on this package with no sacrifice downstairs-getting it to fit under the hood is up to you! Running only a 1-inch spacer will cost you about 5 hp on top.
The engine runs best with 41 degrees of advance; varying the total timing more than 2 degrees either way costs 5-10 hp. Seemingly, that's a lot of timing for a small-displacement, small-chamber engine running on pump gas, but other engine builders report similar advance requirements with Isky Megacams. With the Performer RPM, the engine made 369.1 lb-ft peak torque at 4,500 rpm and 387.5 hp at 6,250. The Victor Jr. shifted the curves higher, making 370.1 lb-ft of torque at 5,000 rpm and 401.5 hp at 6,500. Both combinations made over 1 hp/ci from 4,500 through 6,750 rpm and over 300 lb-ft of torque from 3,000 through 6,500.
The Victor makes more overall average torque than the Performer throughout the 3,0006,750 test-rpm range (356.3 lb-ft compared to 342.9 lb-ft) and more overall average power (362.7 hp compared to 365.8 hp). Over 5,000 rpm, the Victor also beats the Performer, making more average torque (344.9 lb-ft versus 333.8 lb-ft) and power (383.3 hp versus 370.6 hp). On the opposite end, the averages are reversed; the Performer did better than the Victor from 3,000 through 4,750. The Performer develops an average 356.3 lb-ft of torque versus the Victor's 342.9 lb-ft and an average 365.8 hp versus the Victor's 362.7 hp.
The Victor's 1.3 hp/ci output at peak power is an impressive achievement for a single-carb, normally aspirated engine running on 92-octane gas. A measure of how well an engine breathes, this engine's volumetric efficiency (VE)-the ratio of the actual mass (weight) of air taken into the engine to the mass the engine displacement would theoretically consume if there were no losses-never dropped below 100 percent with either intake manifold. VE reached a high of 115.7 percent at 5,500 rpm with the Victor Jr. VE numbers in excess of 100 percent on an unblown engine are usually only seen in full-race combinations with a perfectly matched intake, exhaust, and camshaft combination.
For full-throttle performance on occasionally driven cars, the Victor Jr. is the best intake for this combination, but its relatively high-rpm torque and power peaks require gearing the car accordingly. By contrast, the Performer's dual-plane configuration should make it more driveable at part-throttle, and you're only giving up about 15 hp on the top end.
Check out the sidebars below for details on the major components.