Engine Build: Blown Early Hemi Makes 670 Horsepower
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Building a blown first-generation 392 Hemi for a ’32 Ford hot rod is certainly a worthwhile project that will turn heads and shake the streets along a cruise. But finding suitable parts to withstand the boost and create a streetable powerplant from a foundation that is more than 50 years old can present noble challenges.
A Wyoming-based customer recently approached Borowski Race Enterprises in Rockdale, Illinois, with an original 1957 392ci Hemi engine that had been massaged slightly by another machine shop. Taking on another shop’s project always sends up a red flag, and the customer had a few specific requests to honor, as well.
“This customer will typically bring us one job like this a year,” says Borowski engine builder Dave Livesey. “He wanted it to run on pump gas, blown with dual carbs and a hydraulic roller cam.”
With that in mind, Borowski worked out a game plan that would provide sharp throttle response and horsepower in the 650 range.
The projects starts with a surviving Hemi block-head-crank combination — it’s not an earlier 354ci engine converted to 392. The customer had owned the engine for several years, saying that it languished in another machine shop near the owner’s hometown in Wyoming. That shop had already decked, bored and honed the block before Borowski received it.
“He had talked to us on several occasions about this engine and finally brought it to us,” explains Livesey, noting that picking up a build from another shop can be a scary proposition, “It’s the nature of this business. Different shops use different finishes for the cylinder walls, but it ended up that part was good.”
The first-generation early Hemi is not nearly as common of an engine as its big-block offspring. As such, tracking down parts for these engines can be a chore.
“I was surprised at how difficult some of the parts were to find, since Nostalgia Top Fuel had to run a 392 Hemi engine until recently,” says Livesey.
With no specific 392 Hemi connecting rods available, the customer preferred a set of custom Crower billet steel rods. Livesey admits the rods are overkill for an engine of this output, and he later discovered that big-block Mopar 440 rods could have been substituted. This would have required a different piston package. The JE Pistons are custom ordered to yield a 9:1 compression ratio.
The stock forged-steel crank needed no additional machining and was laid in King main bearings. ARP studs are used throughout the build. Livesey chose a custom ground cam from Bullet Racing Cams and installed it at 109 degrees intake centerline, a 3-degree advance from stock. A Cloyes double-roller timing chain turns the cam.
A Chrysler 340 oil pump conversion from Hot Heads was also installed. This is a common upgrade for early Hemis. The 340 oil pump flows 30 percent more oil volume than the original design. Hot Heads converts these pumps to be a direct bolt on and upgrades them to use a chromoly driveshaft. The oil pan comes from Steff’s, and a K&N oil filter holds back the grime. Hot Heads also supplied the trick freeze plugs.
The customer specifically wanted hydraulic rollers in the valve train, so a set of Crane Cams link-bar lifters were installed. At the end of the Smith Brothers 5/16-inch-OD pushrods are Titan billet rocker assemblies. These rockers will bolt to either a stock Hemi or aftermarket heads and utilize an Allen-head adjustment.
Pushrods are a particular concern when building an early Hemi. The passages in the heads are quite small, limiting the potential outside diameter of the pushrod. With a mild a hydraulic roller cam, a large diameter pushrod was not necessary for this engine. but further machining would have been necessary with a more aggressive cam package.
The Hemi, of course, is legendary for its cylinder head design. As such, the stock heads required no additional machining but did receive a good cleaning and valve job. Complementing that work is a fresh set of stock-sized valves from Racing Engine Valves (REV), as well as Comp Cams springs, locks and retainers. Cometic multi-layer steel (MLS) head gaskets provide the sealing when the ARP studs are tightened.
Until recently, the only water pumps readily available for the 392 Hemi have been a rebuilt versions. Reliability of these was sometimes questionable, and the original pump design is not as heavy duty as today’s modern castings. Hot Heads solves that problem with an adapter kit mount a big-block Chevy water pump. Other cooling tricks from Hot Heads included water-passage block-off plates and BBC thermostat housing.
The customer also already owned the polished BDS 6-71 supercharger that was recently refreshed with new seals and gears. Hot Heads supplied the blow-off valve in addition to the valley cover.
“The parts we ordered from Hot Heads were very high quality, fit well, and didn’t require any additional fabrication to get them to fit,” praises Livesey.
With the supercharger set in place, attention turns to what was going to top it. Weiand supplied the dual-carb adapter plate. Feeding the entire setup is a pair of boost-referenced Holley HP 950cfm carbs that are secured with Moroso studs. Weiand also supplied the stainless dual-feed fuel line kit.
Five dyno pulls were performed to break in and tune the engine. All runs were made on 92 octane pump gas. The engine was filled with eight quarts of Brad Penn 15w40 high performance engine oil. The engine made peak power of 673 horsepower with 10 psi boost at 6,000 rpm. Torque peaked at 648 lb-ft at 4,600 rpm. Carburetor jetting was adjusted towards the lean side with air fuel ratios in the 12.1:1 to 12.2:1 range at peak horsepower.
“This engine is not going to be run any harder than it was on the dyno,” says Livesey, noting that the goal was to provide crisp off-idle throttle response and acceleration. “It’s going in a 2,500-pound rat rod.”
The lakes-style headers also contribute some to the lean numbers. The customer will run a full exhaust on the rat rod and cap the headers, which will fatten up air-fuel ratio. Also, living 5,000 feet above sea level in Wyoming will also richen the mixture. In fact Livesey beleives the engine may need to be jetted even leaner due to the altitude to maintain the desired throttle response.
The build took six months with parts delays causing much of the stretch. Now that it’s delivered, the blown Hemi will add nostalgic flare and street racing demeanor to a hot rod, while giving it impressive, yet streetable, performance. Livesey says the customer’s next project is a blown Ford Boss 429 engine. Wonder if it’s going in a Mustang or pickup truck?
That's a pretty bitchin' early HEMI. More power than a new 8.4L SRT Viper!