For all of the machine work and dyno testing for the Battle of the Titans series, we will be working with Johnson Machine Service of Monrovia, California, which has been building quality race engines for decades. JMS's impressive facility offers a knowledgeable and helpful staff, quality machine work, a DTS dynamometer, and very reasonable prices. So sit back and see how we made the 360 a contender. You'll have to wait till the November issue's final installment for dyno results, though, as we're keeping them a secret even from the rest of the staff until they've completed the Ford and Chevy entries in our Titans shootout.
Cylinder HeadsThe most significant factor in horsepower production for any engine is the cylinder head. Because cast-iron production cylinder heads were mandated, our choices were limited. We debated using late-model production Magnum heads as well as Mopar Performance's big-valve Magnum RT castings but found both to be cost-prohibitive thanks to the need to update to a specific valvetrain (the Magnum engines were the first Mopar V-8 engines to incorporate a stud-mounted rocker arm in place of the ubiquitous shaft system). Also worth taking into consideration is the intake manifold selection available for the Magnum cylinder heads. Since we were mandated to use a dual-plane intake, the only offering is a low-performance dual-plane offered by Mopar Performance best suited to towing duty. The best remaining alternative was a 360 casting rebuilt by Aerohead with 2.02/1.60 intake and exhaust valves. While not as good on the exhaust side as some later-model castings, mid-'70s 360 smog heads feature greater cross-sectional area through the pushrod restriction. Also guiding our choice is the fact that these heads are readily available by mail order from Aerohead Racing. Aerohead offers 360 castings with 2.02/1.60 stainless valves, a three-angle valve job, hydraulic valve springs, 7-degree locks, bronze guides, and chrome-moly retainers for only $499 a pair plus shipping. An additional 100 bucks gets you the 915/587 castings that purportedly have a slightly larger intake port volume. We opted for the 587s and specified hydraulic-cam valvesprings able to accommodate up to 0.580-inch lift for no extra charge.
Bump And Grind: Cam SelectionA hydraulic flat-tappet cam is the name of the game here, so revs will be kept below 6,500 rpm, fitting nicely with our stock cylinder heads. Crane Cams came through with an off-the-shelf hydraulic grind that on paper seems pretty lumpy. We opted for enough lift to assist with torque production and enough duration to crutch the limited flow of the stock cylinder heads.
Camshaft SpecsManufacturer: Crane CamsPN: 694571Grind number: H-312-2Advertised valve lift: Intake/exhaust 0.528/0.552 (1.5:1 rockers)Advertised duration: 312/322 degreesDuration at 0.050-inch lift: 242/252 intake/exhaustInstalled intake centerline: 103 degreesLobe separation angle: 108 degrees