Our heads were expertly ported by Dave Vizard's righthand man-Head Porter Gilbert Mink-to
The cam can't do its job unless it is effectively hooked to the crankshaft. In a stock rebuild, cam drive considerations are fairly straightforward-just pick the chain drive of a quality that suits your performance level and wallet, bolt it in, and go. With our roller cam and our intended initial dyno mule application, we had a few extra considerations. A flat tappet cam has a taper built into the cam lobes, which provides a slight rearward force on the shaft, and keeps the cam in contact with the thrust face between the block and cam gear. With a roller cam's flat interface at the lifter's contact, this force is no longer there, meaning some method must be employed to keep the cam from sliding forward out of position. The usual approach is to use a thrust button or roller at the nose of the cam, and, if the stock timing cover is used, the face should be reinforced to eliminate flexing of the thin, stamped cover.
Since we could foresee testing cams in future dyno evaluations, we wanted a drive system that provides absolute dead-on valve timing accuracy, easy cam phasing adjustment (advance/retard), and easy access to the cam while valuable dyno time is ticking. The only drive system we know of for the Mopar big-block that provided all these requirements, and has an advanced thrust control system built in, is the Milodon Pro Gear Drive.
Gilbert also cut the new 30-degree intake seats for the huge Manley intake valves, and 45-
Basically the same system, which is the standard in top drag classes, the Milodon drive is a single idler system, with its fixed idler running in a sturdy aluminum cover. This setup is the real thing-a far cry from the cheaper, floating dual-idler geardrives. With a single fixed idler, the gear lash is precisely set, minimizing timing irregularities. It's a fact of life that even the best chaindrive systems will stretch over time, changing and varying the cam timing. With the Milodon drive's hardened gears, once the timing is set, it's set to stay.
With Milodon's geardrive, a separate O-ringed camshaft cover plate allows access to the cam without the usual drill of pulling the damper and disturbing the gasket seal at the oil pan when pulling the timing cover. By simply removing the access cover, the cam can be removed, or the cam phasing adjusted by means of the drive's Vernier two-piece cam drive gear. Behind the cam gear is a needle-roller thrust-bearing pack, and at the front, a thrust face is built in, holding the cam in position. The whole package is a bolt-in deal, requiring only that the front-block dowel pins be redrilled to set the clearance between the gears. The only caveat is that the added thickness of the aluminum cover means the water pump must be spaced out about .200-inch (spacers are part of the kit) for clearance. This means the stock water pump pulley will no longer line up. Sure, it'll give us that distinctive "come and get me copper" geardrive whine, but that's music to our ears.
The heads then were taken to M&R machine in Glendale, California-which handled all our bas
The heads were assembled with a $20 lever-action valvespring compressor from Harbor Freigh
Running dual springs means the spring seats must be machined for clearance (arrow A), and