Mike Petralia, owner and chief bottle washer at Hardcore Horsepower & Dyno in Franklin, TN, is no stranger to hot small block Ford builds. So when it came time to do another one, he wanted to zig where everyone else had zagged. The goal was big power and big cubic inches from a high compression, naturally aspirated combination.
The foundation was a 4.125-inch bore Dart SHP iron block and a 4.100-inch stroke Scat forged steel crankshaft. The longer stroke also required long rods, so Mike went with 6.200-inch Scat H-beam rods designed for small block Chevy rods. The reason for the mouse rods is due to the Scat crank’s 2.100-inch diameter rod journals, which are the correct size for small block Chevy rods. That allowed Mike to choose from a much larger pool of connecting rods. The block/crank/rod combination yields 438 cubic inches—a bunch for a small block Ford.
Mike dove into the JE Racing catalog and found a set of forged pistons for the build. They had an advertised +6.5cc dome, 1/16-1/16-3/16-inch ring lands, and a .927-inch pin bore that matches the small Chevy rods. The other important factor was the 1.230-inch compression height. If the Dart block was milled down to a 9.480-inch deck height, the pistons would be very close to a true “zero” deck (piston top even with the cylinder bore opening), which is great for making naturally aspirated horsepower. Total Seal Maxseal piston rings sealed the deal. The file-fit rings feature a ductile-iron gapless top ring, 1-piece Napier-style second ring, and reduced-tension oil scrapers that would work well with the vacuum pump Mike planned to run.
Cylinder Heads and Valvetrain
Mike wanted the 438 to be a true “Windsor.” That meant no cheating by using a set of Ford Cleveland-style heads. Trick Flow had exactly what was needed with its CNC-ported High Port® 240 aluminum heads. The High Ports are designed for large cubic inch engines or smaller engines running lots of nitrous or boost. The heads have 240cc intake and 95cc exhaust runners finished off with Trick Flow’s high resolution CNC Competition Port work for maximum flow and velocity. Mike had the heads flat-milled to reduce the 67cc combustion chambers down to 62cc. With the JE pistons, compression came out to 13.90:1.
Mike found a nice solid roller cam with specs that looked really good on paper. But when he test-fitted the cam in the 438, there was literally zero piston-to-valve clearance. He turned to Comp Cams for a custom grind. Hardcore Horsepower has worked closely with Comp engineers many times trying new ideas and making big power, but this one turned out to be a tough challenge. Comp had to build a cam with lobes that would meet the power and rpm goals, and it had to fit in the engine as-built.
The result was a solid roller with over .740 inches of valve lift. The cam had .017-inch less intake and .020-inch less exhaust lift at Top Dead Center overlap—the critical point for piston-to-valve clearance—but had the same .050-inch duration and more total exhaust valve lift on the exhaust side than that first “paper” grind! You can read more about the importance of lobe lift at TDC overlap at the end of the story.
The 460 lbs./in. valve springs installed on the Trick Flow High Port heads were rated to .680-inch max valve lift, but Mike wanted something a bit stiffer to control the gnarlier Comp Cams bumpstick. He swapped the spring for a set of stiffer 640 lbs./in. Crower springs. Considering the heads’ large 2.10-inch intake valves and the faster acting 1.7:1 Jesel shaft rockers used, the Crower springs provide better valvetrain stability at higher rpms.
Mike also got a set of Comp Cams Hi Tech pushrods. The 3/8-inch diameter, .135-inch wall pushrods offer a lot more stiffness to complement the Crower springs, but also needed a lot more clearance to run. The pushrod holes in the Trick Flow were milled to get the proper clearance.
The Milodon Racing oil pan is designed to fit the common Fox-body chassis. Mike found some spots that needed extra clearance, like around the Dart block’s large billet steel main caps. The oil pan’s extra-wide passenger side kickout limited starter clearance, even when using a Powermaster high torque mini starter that can be clocked to clear most headers and oil pans. The pan was massaged to fit.
Mike used a Trick Flow R-Series intake manifold and a 950 cfm Trick Flow by Quick Fuel double-pumper carburetor. The manifold was port-matched to the High Port heads; the carburetor was run right out of the box.
Mike had to machine custom spacers to properly mate the front engine accessories—a Powermaster alternator, MSD crank trigger, GZ Motorsports vacuum pump, and a Meziere Enterprises billet electric water pump. Luckily, the water pump had dual-side inlets allowing the lower radiator hose to mount on the driver’s side of the engine. Otherwise, you’d never be able to see the timing pointer.
To really set this build apart, the Trick Flow cast valve covers were painted to match the engine block’s classic VHT Ford Light Blue color.
During the dyno session, Mike found some power with carburetor jetting and air-bleed modifications and some timing adjustments. Best peak power (735 horsepower) was found using a two-inch tall HVH Super Sucker carb spacer. Mike also tried a 1 7/8-inch tall Wilson Manifolds open spacer that sacrificed about four horsepower at the top end, but added 12 ft.-lbs. more peak torque (621 total). Either spacer combined with the already-tall Trick Flow intake put the carburetor pretty high above the engine. If you run this engine in a car, a giant hood scoop is definitely in order!
Summit Racing put together special engine combos to help you duplicate the build.
Piston-to-Valve Clearance: It’s Not About Maximum Lift
When inexperienced engine builders talk about piston-to-valve clearance (PTVC), they always think it’s about maximum valve lift. That’s not the case at all as the pistons are never anywhere near the valves at maximum lift. The clearance issue happens when the piston is at or near Top-Dead-Center, with both valves still open during the overlap cycle of the cam. The amount of valve opening at this point is critical, and can be affected greatly by the cam’s Lobe Separation Angle (LSA). A wider LSA (114°-118°+) will keep the valves a bit further away from the pistons at TDC-overlap. A tight LSA (110°-104° or less) will put the valves closer to the pistons at TDC-overlap. Advancing or retarding the cam can change piston to valve clearance as well.