Inside the Butler-MacMaster Engine Shop

The topic of sealed or spec engines will never enjoy universal harmony in the racing community, but one shop near the capital of Maine takes a pro-active approach and strives to ensure that the positive aspects of the program are safeguarded.

“It’s allowed a lot of teams to afford running in a premier touring division,” says Joe Connors, general manager at Butler-MacMaster Performance Engine Builders in Hallowell just off I-95 south of Augusta.

A sealed Ford crate engine built by Butler-MacMaster for circle-track racing in the Northeast.

B-M builds around 80 sealed engines a year for teams in various circle-track sanctioning bodies competing in the Northeast, primarily the American Canadian Tour, Granite State Pro Stock Series and the Pro All Stars Series. The shop focuses primarily on five starting crate-engine foundations: the GM 602, 603 and 604 along with Ford’s 347 Jr and 347 Sr.

“It all depends on the sanctioning body, but our most popular are the GM 603 and Ford 347 Jr.,” adds Connors.

Standing near the shores of the Kennebeck River, B-M’s 10,000 square-foot facility boasts a fully equipped machine shop and two engine assembly areas – one dedicated to race engines and the other for a wide variety of marine, industrial, and street-performance applications.

“If it’s got a crank, rods and pistons,” boasts Connors, “we’ll work on it!”

Started in a garage

Indeed, when we called there was a 5.9-liter Cummins, a 534ci Ford marine V8, an AMC 390ci V8, a Buick 3.8-liter turbo V6, 1968 Vauxhall and a 1940 Ford Flathead on the shop’s work schedule.

“We’ve done everything from a 1-cylinder Kohler to a Cat C15,” adds Connors. “On any given day, we could be working on a GM crate engine or a John Deere diesel.”

It’s been a good program for the budget racer. — Joe Connors, Butler-MacMaster

The shop’s genesis traces back to the late ‘70s in the home garage of Dave MacMaster, who later teamed up with Marty Butler to launch operation in current building in 1983. Butler retired about 10 years ago. In January 2012, Melton Industries out of New Jersey acquired Butler-MacMaster. Melton services heavy-duty industrial equipment and had a working relationship with B-M over the years. MacMaster stayed on as a consultant for 16 months, then recently retired.

Butler-MacMaster handles considerable volume in cylinder-head service. Note the variety of diesel, racing and restoration applications in this series of photos.

Busy dyno room

Today the shop has seven employees and has the equipment to support cylinder head work, including seats and guide, valve jobs and and resurfacing. Block work includes boring and honing on the cylinders, mains and lifter bores. Other equipment handles connecting rod reconditioning, crankshaft grinding and polishing, camshaft polishing and balancing of the rotating assembly. B-M also has different test methods to discover cracks or other imperfections in parts as well as pressure tests to ensure all engines leave the shop leak-free. Finally, there’s a SuperFlow SF 901 dyno to validate the horsepower.

Industrial and Marine Engines

Whether it’s a positive sign for the economy or just a cyclical response, industrial repairs are now a big percentage of Butler-MacMaster’s workload. The shop has also been seeing more marine engines, from lobster boats to family cruisers. Shown here are a couple of examples. Top is a John Deere 276 that the owner wanted orange instead of green. Below is a unique Hercules straight-6 used in a boat restoration.

“We’ve had it at least 20 years,” praises Connors. “I can’t tell you how many engines have been across that dyno. It’s going two or three days a week, every week of the year.”

The dyno is an extremely important step in the validation of the sealed engines for racing. For example, the ACT series has a ceiling of 360 horsepower. B-M runs every sealed engine to ensure they’re within an allowable percentage of that limit while maintaining the legality of the parts and construction.

A typical sealed-engine job starts with delivery of the crate engine, and then the B-M team installs the necessary parts to improve durability. The GM 603 is actually part number 88958603 and is described as a ZZ4 350 adapted for circle track racing. GM rates it at 355 horsepower at 5,250 rpm with peak torque of 405 lb-ft at 3,500 rpm. The engine comes with 4-bolt mains, forged steel crankshaft, powdered-metal steel rods, hypereutectic pistons, hydraulic roller cam, 10:1 compression ratio and ZZ4 aluminum heads with 1.94/1.50 valves and 163cc intake ports.

While the engine comes with a racing-style oil pan and HEI distributor, B-M swaps on a Moroso oil pan and a MSD distributor.

“Dave worked with Moroso years ago to help design this pan,” says Connors. “Later we came out with a shorter version so teams can lower the engine in the chassis. We have a choice between 6.5- and 8-inch depths.”

Two-years racing before servicing

B-M also removes the standard stamped-steel rocker arms in favor of Scorpion roller rockers, although maintaining the 1.5:1 ratio. Other upgrades include ARP rocker studs and main bolts, a smaller BHJ harmonic balancer and steel timing cover in the place of the stock plastic. The engine is also prepped with the necessary plugs, seals and gaskets. Rules require a 500 cfm 2-barrel carb.

Butler-MacMaster offers a full machine shop to prep blocks and rotating assemblies.

“Most teams already have their own carbs built to their liking, so we’ll run those on the dyno,” says Connors, adding that the final step after dyno testing is sealing the engines and recording the appropriate serial numbers.

A SuperFlow SF-901 anchors the dyno room

If it’s a new engine, B-M suggests that the teams run them two years before a routine off-season freshening that includes rings, bearings, valves, valve springs, cylinder hone and crank polishing.

“Then they can run another two seasons before we have to put in new connecting rods,” says Connors. “These crate engines have been bulletproof. We really haven’t had any mechanical failures.”

B-M ships out all sealed engines with Brad Penn 20w-50 oil and recommends 2-week change intervals on a normal racing schedule that includes 35- to 40-lap features.

Also supplies ‘built’ engines

“It’s been a good program for the budget racer,” says Connors. “It’s kept the competition close and helped teams that couldn’t afford a ‘built’ Pro Stock engine want to run in a touring series.”

Examples of drag and circle-track engines from Butler-MacMaster.

A turnkey GM 603 crate engine sells for just over $7,000 and a freshening will run just under $3,000. Ford’s direct competitor, the 347 Jr. crate engine, is similar in price and preparation, except that it comes with roller rockers and suitable rocker studs. Ford rates it at 350 horsepower at 5,500 rpm with 400 lb-ft of torque at 4,000 rpm. It features a 10.5:1 compression ratio, Scat forged crankshaft and rods, Mahle pistons, Comp Cams hydraulic roller camshaft, Ford’s “X” head with 1.94/1.54 valves and a MSD distributor.

There are two engine assembly areas at Butler-MacMaster.

“It comes with a race pan but we do some modifications to it,” adds Connors. “And it also comes with a smaller balancer.”

B-M is also keeping up with new engines approved for competition and also assembles “built” engines under the rules to compete against the sealed engines.

“I’ve got one team that has a 604 crate engine and a 9:1 ‘built’ engine,” says Connors.

Cross training

Beautifully restored Ford Flathead ready for a customer.

B-M’s racing expertise spreads across numerous disciplines. They’ve worked on everything from drag racing to truck pulling. The marine and industrial builds are also an important part of the overall success, which requires a diversified staff.

“Everyone’s been cross-trained but I keep them where they’re most proficient,” explains Connors. “One guy will do the heads, one guy does the block work. Also, one person assembles the race engines and the other builder assembles the marine and muscle-car engines. Industrial is the most rapidly expanding area of the shop.”

Butler-MacMaster is located in Maine, just south of the capital city in Hallowell.

Workflow is based on several factors, depending when the job came in, type of work, parts availability, and necessity.

“If it’s a cylinder head off a skidder and that’s how the guy makes his living, I’ll try to prioritize that,” says Connors. “If someone has a race coming up on the weekend, then we do everything we can to finish that engine. If it’s a restoration, then that’s usually more of a long-term project.”

Butler-MacMaster also offers products and packages for import and compact cars, including turbo packages in addition to support and replacement parts for race vehicles. For more information, visit the shop’s website at

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About the author

Mike Magda

Mike Magda is a veteran automotive writer with credits in publications such as Racecar Engineering, Hot Rod, Engine Technology International, Motor Trend, Automobile, Automotive Testing Technology and Professional Motorsport World. He was the editor of four national automotive magazines, including Chevy High Performance, and has authored hundreds of automotive technical briefings. In covering nearly every type of motorsport, Mike has collaborated with many of racing's top engine builders and factory engineers.
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