6.1L Hemi in a 1972 Plymouth GTX - Horsepower!
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426CI 550HP Hemi
Matt Delaney, Delaney Auto Design, Shreveport, LA
Car Craft held our first Engine Swap Drags event at Firebird Raceway in Phoenix over the last weekend in April this year. It was open to any new engine, modular, LS, or 5.7/6.1 Hemi in a pre-'92 car, and we had a total of zero Hemi swaps show up. Maybe we didn't cast our net wide enough, maybe Phoenix was too far for a potential competitor, or maybe we need to publicize the event better next time around. In any case, we wish Matt Delaney had shown up with his '72 Plymouth GTX. Though the valve coverq say 6.1, this is actually a bored and stroked Mopar Performance 392-inch crate engine. Matt's big-bodied GTX was on display at last year's SEMA show. Judging by the missing fenders, we're guessing this picture was taken before the show.
Fortunately, the engine compartment of his big B-Body was accommodating enough to accept the new Hemi with minimal headaches. Using an AlterKtion K-member, he was even able to keep the factory A/C compressor in the stock location. "I live in Louisiana; I have to have air conditioning."
B. Extra stuff
There's a Keisler A41 four-speed automatic transmission behind the Hemi, and the car rolls on a coilover front suspension and a triangulated four-link setup in the back. Matt says his car will post low 12-second e.t.'s and knock down 26 mpg on the highway.
For those of us without the conversion factor hard-wired in the brain, 6.1 liters is roughly 372 ci. Mopar Performance's 392 is about 6.4 liters, but Matt ponied up for even more displacement. He had the block bored 0.020 over and plunked in a 4.05-inch Callies stroker crank. Those changes get you up to almost 423 ci, which is close enough that Mopar guys call this combination a 426. Manley rods and Diamond pistons round out the short-block. Stanton Racing Engines ported the cylinder heads, and Matt says they flow like crazy. The compression ratio is a totally streetable 10.0:1, and Matt kept the cam that came with the engine package. The specs are 229/236 degrees at 0.050 inch, 0.584/0.552-inch lift on a 110-degree LSA. From Mopar, these 392 engines make about 540 hp and 490 lb-ft. With the bigger displacement, Matt says his engine is producing about 550 hp and a whopping 570 lb-ft.
This single-plane intake manifold is from XV Motorsports and was designed to work with either a carburetor or aftermarket electronic fuel-injection kits that utilize a top-mounted throttle body. The advantage to this is the owner can keep the cool Shaker or air grabber hood functional even with EFI on the new-generation engine. This particular throttle body is from Holley. Matt likes it because it uses the same idle air control motor the 392 crate engine comes with. Therefore, he can still use the Mopar Performance ECM that comes with the crate engine rather than switching to a different stand-alone engine management system.
The brackets and accessories are the same as you'd find on a Charger or Challenger. The power steering pump is from an SRT8 Cherokee because it mounts the reservoir on the pump. "This is all stuff you can buy at a Dodge or Chrysler dealership brand new for about $900," Matt told us. That way, it is easy for his customers to get replacement parts if the need arises.
This is a really cool GTX.