Porting

["James J." <m1garand@speakeasy.net>]

I'm lucky to have an excellent machinist, who is a retired engine 
builder for a Busch series team, and now runs the engine lab for 
University of Maryland in the upstairs of his shop.  He has wet and dry 
flow benches, ultrasonic gear and precision cam profiling gear, and most 
importantly, the incliniation to teach and share.
A few nuggets he passed to me were:
1) Mirror polishing the intake reduces turbulence, but allows for fuel 
puddling (even with EFI, but not so critical with direct shot heads, 
like the LS1 and LS6)
2) Having a little step-up along the bottom of the port between the 
intake manifold and head also creates a little shear turbulence which 
helps keep fuel in suspension
3) If your shop has modern precision valve and seat grinding equipment, 
never lap the valves, as the abrasive paste will never completely go 
away, and will ultimately destroy the seal.  His gear can cut valves and 
seats surfaces to tighter tolerances than exists between the valve stem 
and valve guide, so valve wobble is the limiting factor.

Even though I had him street-port my aluminum 300 heads, it would have 
been too expensive to take it to the max with ultrasonic thickness 
checking and flow-benching.  Since there is almost no published data on 
the internal dimensions of the 300 heads (unlike Chevy and Ford heads) 
he had to be very concervative.

My next step with him is deciding the optimal ram length for the Rover 
EFI pseudo-individual runners in a sports-car application (stock Rover 
length is for low-end SUV torque)

JJJ

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