I ported flathead blocks on a waist-high workbench for nearly ten years before I figured out a better scheme – a two-axis gimbaled fixture that allows me to position a block exactly as I want it, and quickly alter its position, in small or large increments, in almost any two-axis global orientation. Designed to fit a conventional engine stand, it also fits nicely into a socket welded to a steel post in my porting area. In the X axis, the fixture indexes at 45-degree increments for a full 360 degrees of rotation, and in the Y axis it indexes infinitely through all 360 degrees of rotation. The big plus for this type of fixture is that tool application is always in the most-effective direction, which is generally in the 3 to 9 o’clock positions. As a consequence, tool control is excellent, critical cuts and surface finishes are optimum, and fatigue is greatly reduced.
I could have built the fixture with chamfered and welded corners, but
Art Morrison Enterprises was starting to do neat hot rod and racecar frames with their new mandrel-bending gear for rectangular tubing, so I figured why not?
A full-size Ford/Mercury block is positioned in the fixture with the camshaft centerline lined up with the Y axis axles. This corresponds with the longitudinal CG – or nearly so; the block can be held with very little drag on the drag bolt and is easily rotated when the drag is loosened. A V-8-60 block sits just a taste higher to feel neutral.
A year ago a pal asked me if I would port a set of Chrysler Hemi heads for a vintage dragster he was restoring. Sure, I just needed a couple of angle plates to bolt to the end plates in the fixture that a head could sit on and be secured with bolts.
Suddenly, several aluminum cylinder heads from Yamaha SR500 singles showed up, needing porting, of course. (These motors are popular and successful in AMA dirt-track racing.) This time a simple bridge of 1/8-inch stainless, with a 45-degree break on each long edge to stiffen it, neatly supports a head.
Finally – or maybe not – Vern Tardel showed up with a big ’49 Lincoln flathead block destined for another vintage dragster. Longer extension plates supported the big block which is secured with bolts in the main-bearing saddles on the ends. This monster sits lower in the fixture; lined up on the camshaft centerline, as I originally did it, it was an unwieldy pendulum. Dropping it about an inch did the trick and it rotates as easily as the smaller blocks.