PRI 2018: AJPE’s Raised-Cam Hemi, Water-Jacketed 481X Blocks

Multi-time championship-winning car owner and crew chief Alan Johnson and his California-based Alan Johnson Performance Engineering may be virtually synonymous with Top Fuel and Funny Car racing, but there’s far more to the company than simply nitromethane blocks and cylinder heads. With the rise in Pro Modified and drag radial racing, the company’s engineers have developed billet parts catered to the needs of those markets, and some of its latest iterations are on full display here at PRI.

Among the latest and greatest is its new raised-camshaft billet Hemi for some of your more extreme Pro Modified and Radial versus The World combinations.

“This is the last creation in our Hemi engine platform, designed for outlaw Pro Mod-style racing,” says AJPE’s Rick Wilkinson. “This raised-cam Hemi has a 70mm camshaft core in it now. We’ve removed the inner head stud like normal Hemi’s would have and changed the head bolt pattern so you can take the cylinder head off without having to remove the manifold. that’s really a big part of it — for servicing between rounds, you don’t have to disassemble the fuel injection stuff or take the supercharger off.”

With moving the camshaft up, AJPE has also changed the lifter angle to improve liter alignment with the pushrod and rocker geometry. They also developed a one-piece girdle to tie the entire rocker assembly together strongly to the cylinder head.

Pro Line, which partnered with AJPE in its PRI Show exhibit, built the first engine using the raised-cam Hemi from AJPE for customer Sidnei Frigo, who won the NHRA season finale in Las Vegas with it between the framerails.

“This engine seems to run better at higher rpm — it’s mostly a result of valvetrain related efficiency,” Wilkinson explains. “The short block is the same — same bore and stroke and same cylinder head design. A normal cam tunnel on a Hemi only has five bearings, and the front bearing on the Hemi is a pretty wide span from the number one to number two, and we’ve actually added a sixth bearing in there to support the came bore. so that’s part of it, as well. We would find with the old version that the front springs would tend to lose pressure and go down faster than the rest of the engine — we believe there was some flex inherent in the system and so we removed that.”

AJPE has also built a water-jacketed 481X block, which is the same used in many of Pro Line’s record-setting 481X powerplants; they are also working currently on water-jacketed cylinder heads to go along with the block. A big-block Chevrolet-based platform, the water-jacketed 481 appeals to the Top Dragster/Top Sportsman crowd, no-prep racers, and others. Wilkinson adds, “this engine looks like a big-block Chevy, uses some big-block Chevy components, so it fits that type of guy that wants a Chevrolet-based engine. It’s durable, reliable, and guys like it because it’s easy to work on. And it makes great power.”

About the author

Andrew Wolf

Andrew has been involved in motorsports from a very young age. Over the years, he has photographed several major auto racing events, sports, news journalism, portraiture, and everything in between. After working with the Power Automedia staff for some time on a freelance basis, Andrew joined the team in 2010.
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