The original Edelbrock Tunnel Ram manifold for either small- or big-block Chevrolet contained runners to significantly-larger cross-section areas than the manifolds from Weiand.  Racers using Weiand manifolds at the time, including Bill, claimed a broader and improved torque band, largely based on slightly smaller runners.  Elapsed times seemed more improved than terminal speed, obviously a benefit to drag racers.

After some discussion to see if he’d be willing to try an Edelbrock big-block manifold of slightly different internal dimensions, he agreed to give it a shot.  What followed was a flow bench exercise that led to sizing the runners specific to the four “good” and four “bad” cylinder head ports, the objective being to improve net torque over the production Edelbrock manifold.  When completed, and by viewing the manifold from the cylinder head flange side, the four “bad” ports had runner cross-section areas (at the heads) that were much smaller than the head ports.  As much as 5/8-inch of overlap existed at the runner floor and push-rod side of the head ports.  And again, nothing was detectible from outside the manifold.  If memory serves, it was worth about 1/10th second quicker than what Bill had been running… in a era when that amount of reduction was considered worthwhile.

But there was one occasion when this manifold “customization” deal back-fired.  We’d been doing some “filed core” intake manifolds for John Lingenfelter and Larry Tores, both then running small-block Chevrolet; John in his Camaro convertible and Larry in his little Chevy II.  For these two different engine combinations, I’d filed some cores to help integrate the manifold with the two different camshafts these racers were running.  Keep in mind that filing cores required a couple of important steps: (1) the foundry had to make special effort to provide solid cores (not shells as in production parts) that could be re-shaped by sanding off certain areas and (2) the machining of such special parts needed to be separate from production manifold machining operations.

Well, the first requirement was obviously met, else there wouldn’t have been any special manifolds to machine.  The problem lay with the second requirement.  I’d tagged the four manifolds with the intention of having them kept separate from a production run.  The day after they were to be finished, when I went to find them for John and Larry, I discovered the parts had been boxed, placed in inventory and shipped the previous day.

Now, what would you have thought if, after purchasing your Edelbrock “Tarantula” manifold, you looked at the port match or discovered non-identifiable distribution fixes not found in other Tarantulas?  I’ve wondered about that numerous times.  But the best laid plans…