SBFW 438 01 LEAD

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.

Short Block

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.

Oiling System

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.

Other Items

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.

Dyno Results

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.

trick flow engine on a stand
marking scat forged crankshaft
measuring crank journals with a bore gauge
using fluid to check combustion chamber volume with pistons
bare engine with camshaft degree wheel
cam retainer plate on an engine
checking combustion chamber volume
exhaust port on a cylinder head
checking valve spring rate on an intercomp scale
drilling larger pushrod holes into a cylinder head
installing valve springs into a cylinder head
close up of an engine oil pan windage tray
trick flow r series intake manifold
engine on stand in workshop
kooks headers installed on an engine
dyno testing an engine
holley dominator carburetor on an engine on dyno
engine horsepower dyno chart results
engine horsepower dyno chart results

The Scat forged crank and H-Beam rods are measured and cataloged for future reference. The crank was also lightened a bit by contouring the counterweights, shaving a few pounds off the rotating assembly.

After measuring the crank journals, Mike Petralia measured bearing clearance in the Dart SHP block and logged those numbers too.

The JE Racing forged pistons measured 50cc @ -.250-inch below deck, which calculates out to a +4.7cc dome volume. The JE catalog listed them at +6.5cc. The lost volume is in the area above the top rings.

The custom Comp Cams roller cam features over .740-inch lift, and was degreed-in at 106-degree intake lobe centerline, two degrees advanced from the 108-degree lobe separation angle (LSA) ground into the cam.

Dart blocks do not include a cam retainer plate or bolts. The oil galley plugs typically stick out too far for the plate to seat properly so you have two choices—tap the pipe threads deeper, or mill the plate's backside to clear, which Petralia did.

Trick Flow Specialties did a nice job CNC-porting its High Port 240 aluminum cylinder heads. They flow 343 cfm intake and 257 cfm exhaust at .700” valve lift. The combustion chambers were milled down from 67cc to 62cc. Combined with the piston's as-measured dome volume of +4.7cc, installed height of -.003" below deck, and the .052" thick Fel-Pro MLS head gaskets, final compression was 13.90:1.

The High Port cylinder heads feature a raised exhaust runner for better flow, and dual header bolt pattern to clear large pipes.

Petralia swapped the 460-lbs./in. springs that came on the heads for stiffer Crower 640-lbs./in. Vasco-Jet H11 springs. After about 40 dyno pulls, the springs were re-checked and showed 240 pounds on the seat, and 710 pounds at 1.200-inch lift. That works out to a 588-lbs./in. rate after break-in, which is pretty typical.

The pushrod holes in the heads have enough clearance for stock 5/16-inch diameter pushrods and 1.6:1-ratio rocker arms. They had to be clearanced for use with the larger Comp Cams 3/8-inch pushrods and 1.7:1-ratio Jesel shaft rockers. The holes were milled with a tapered reamer since the interference was only at the tops of the bores.

The Crower valve springs' large O.D. required the use of smaller 12-point ARP nuts on four studs on each head. That allows a 9/16-inch socket to fit.

The Trick Flow® R-Series Intake Manifold delivers substantial power increases in the 3,500-7,500 plus rpm range on heavily modified street/strip and race engines—exactly what the 438 is. The single plane manifold has integral bosses for nitrous or fuel injection nozzles, and extra material for custom porting. The manifold was port-matched to the High Port cylinder heads.

Here's the 438 dressed in dyno trim, without an alternator.

The big two inch Kook's stainless headers left no room for spark plug wire boots, requiring removal of the headers to check/change the plugs. Some of the header flange was later ground away to create enough clearance to get the boots on and off.

Dyno testing and tuning over a period of a few days produced a 735 peak horsepower and as much as 614 ft.-lbs. of peak torque using a Trick Flow by Quick Fuel 950 cfm carburetor.

A 1,050 cfm Holley Dominator was tried to add more top-end horsepower. Two different carb adapters were used to fit the out-of-the-box carburetor on the 4150-flange manifold. The engine actually made less power with the Dominator, mostly due to the midrange and top-end being way too rich for this small engine.

Peak horsepower was achieved using a two inch tall HVH Super Sucker tapered 4-into-1 plastic carb spacer.

A 1 7/8” Wilson open plenum aluminum spacer helped the engine make highest peak torque (621 lbs./ft. at 5,300 rpm vs. 607 lbs./ft. at 5,200 rpm with the HVH spacer) but gave up four peak horsepower. Petralia says he keeps about 50 different carb spacers in stock because not every spacer is the best for every application.

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.

Share this Article
Author: Alan Rebescher

Editor, author, PR man—Alan Rebescher has done it all in a 25 year career in the high performance industry. He has written and photographed many feature stories and tech articles for Summit Racing and various magazines including Hot Rod, Car Craft, and Popular Hot Rodding, and edited Summit Racing’s Street & Strip magazine in the 1990s. His garage is currently occupied by a 1965 Ford Mustang.