To quote a classic line from a semi-classic television show,
The A Team: "I love it when a plan comes together." Now to be sure,
I needed to look up the source of that line, because even though it has become
a common catch phrase, I had no clue as to the origin. It seems that I just didn’t watch much TV in
the decade of the 1980’s, doubtless due to the transition I was undergoing from
scumbag biker into dedicated drag racer.
In any case, it does reflect my thoughts on the project I am finally
getting around to writing about.
Well over a year ago I received a call from Zach Waters in
regards to porting a set of Knuckle heads.
His plan involved the following:
- Put his 1947 Knucklehead on the salt flats
- Set a record in the appropriate vintage class
- Return the bike to normal street use.
Okay, now that may not sound so terribly challenging on the face of it, but
there were a couple caveats that certainly made things a bit more
interesting. One was that the particular
class in which Zach had slated to compete demanded that externally everything
on the bike must appear stock. The
second was equally interesting from a performance standpoint; the motor would
be left in the same configuration when returned to street use as it had for
Bonneville competition.
 |
| This paint would look more at home in a bike show than on a bike competing at Bonneville |
Everyone would probably agree that one of the keys to speed
is horsepower, and likewise one of the keys to horsepower is airflow. Thus, Zach’s decision to send the heads to
me. But the second caveat, that of
leaving the engine in the same configuration for street use, was a big factor
in every aspect of the build.
 |
| You have to appreciate the classic profile! |
The engine work (outside of the heads) was taken care of by
Bob Moreland of Bob’s Garage in San Marcos.
Foregoing lightened flywheels, Bob instead balanced them to provide Zach
with a short block that runs as smooth as silk. The compression ratio was left low enough to
compliment the mild Andrews “S” grind cam.
You may note that the S grind is the mildest “performance” cam which
Andrews offers for Knuckle engines; the only one less aggressive being deemed a
“stock” replacement. Obviously all of those things enhance the street-ability of the whole package.
For my part, since the heads would soon see full time street
duty, I avoided adding any porting epoxy. Experience has shown me that it tends
to have a limited duty cycle in cast iron air cooled heads. Instead I gave the heads a good porting job
using only 1.950” x 5/16” stem intake valves, along with attempting to manipulate
the boundary layer flow in lieu of adding material. My thinking on the relatively small intake valve
size was that the heads would still readily outflow the M-35 Linkert (mandated
by the rules), and would also insure no material would need to be removed from
the pistons for clearance, sacrificing compression ratio in the process.
Zach credits Phares Cycle for their additions to the quest
for power, along with Jeff Montgomery for guidance in tuning. Of course, the real heroes of the story are
Zach and his dad, who put in the time and effort, not only in research, but
also untold hours of trial and error tuning.
 |
| Ready for action |
The results? Only shattering the
previous record speed by over 15 MPH. I
love it when a plan comes together!
 |
| Verification of Engine Displacement |
Now Zach is quick to point out that even this resounding
success left plenty of room for improvement.
Further tweaking with the addition of dyno time would likely prove
beneficial, as would some experimentation with the gearing since he felt it may
have been a bit higher than optimum. Even
the inconsistency of the salt conditions played a big role in limiting the MPH. Zach’s best run of 107.8 MPH was considerably
faster than the preceding 97 MPH pass which was the result of poor track conditions. This left the two-way average, record breaking
number, at an official 102.4 MPH.
 |
| Do you think there might be a story behind this kicker pedal? |
So, belated congratulations to Zach and his team, along with
a big thank you for allowing me a small part in a plan that definitely came together.