madam and sirs:
it's my feeling that a number of FF engine rules were changed under the umbrella
of a "rewrite and reorganization for clarity" promulgated in the February 2008
Fastrack (see FF p.9, http://scca.org/documents/Fastrack/08-fastrack-feb.pdf)
(ie: not sumitted to the membership for review and comment) . while not as
troubling as the continuing lack of objectively verifiable definitions for key
aerodynamic related terms, with the RunOffs just around the corner the change
to the fastener language is probably worthy of your review and consideration.
as promulgated, D.1.s.1.A now states:
"Fasteners - nuts, bolts, screws, studs,
etc. Intake manifold fasteners may be of either a socket head or hex head
configuration, and must be 5/16” diameter."
the prior equivalent language stated:
"Fasteners (nuts, bolts, screws, studs, etc.) except intake manifold fasteners.
Intake manifold fasteners may be of either a socket head or hex head
configuration."
ignoring for the moment the continuing promulgation of rules that are not objectively
verifiable, the addition of the phrase "and must be 5/16" diameter" is a serious
concern. all of my cast iron and aluminum FF heads (Ford stock and prepared) are
tapped 5/16-18 for attachment/location of the intake manifold and all of my intake
manifolds (Ford stock and prepared) have 5/16" OD fastener clearance holes as
machined at the factory. have I missed for more than thirty years the potential for
approval of an "innovative" rationale that enables re-drilling and re-tapping of
the FF cylinder heads and/or FF intake manifolds just like I missed the rationale
that permits the now public compliance of drilling and tapping of both the 2-liter
Pinto head and cylinder block?? since no tolerance or extent is included in the
"clarifiaction", I wonder about the intent (only curiousity) and worry about the
potential variance in compliance verification given the importance of the RunOffs to
the memebership and the Club.
absolutely nothing is known about the origins and review of the change:
1.) the member's name suggesting or requesting the change is unknown
2.) the objective(s) and benefit(s) of the change are unknown
3.) alternatives considered (if any) and the rationale for their rejection are unknown
4.) the financial impact to the membership is unknown
5.) the nature of the test data (objectively verifiable or not) and/or analysis submitted to those reviewing the draft change is unknown
6.) the process used and the name(s) of those who reviewed the draft change are unknown
assuming, for discussion purposes, the objective of the change was to preclude use
of reduced shank fasteners like shown in the attached photograph, I'd recommend
consideration of:
intake manifold fasteners shall be of either socket head or hex head configuration. with the exception of either the socket or hex head and the first 0.060" beneath the head, the outside diameter (OD) of the fastener shall be 0.3125" ± 0.010" or 5/16-18 thread.
the language is objectively verifiable, precludes the assumed stepped-shank objective of the change prompting this correspondance, AND preserves compliance at no cost for
members who have made the time to procure intake manifold fasteners with the correct
grip length so their aluminum intake manifold aren't supported on sharp steel 5/16-18
coarse threads.
the fasteners shown in the photograph, like lots of other experimental bits and pieces tested from time to time, are not part of my baseline FF engine configuration. the fasteners were made four to five years ago from 180+KSI fasteners purchased from ARP. like so many simple ideas, the real cleverness was in fixturing the fasteners so they could be ground to get both the required corner radius and surface finish
(fatigue life) at the reduced shank diameter (the tooling guy I work with has approaching 40 years of aerospace tooling experience and routinely saves unusual cartoons from the
waste basket). testing of the reduced shank fasteners in that same timeframe on a
National/National plus class engine with a state-of-the-art tuned exhaust showed 1HPc
could be moved from the bottom of the powerband to the power peak OR from the
power peak to the bottom of the powerband (ie:a zero sum game just like seen with tuned exhausts). while the fasteners didn't perform as well as expected, their testing provided invaluable insight into the complex gas dynamics and fluid mechanics of the intake side of a FF engine, the frequency (rpm) characteristics of the mechanical flow filter we know as the intake manifold, and the GCR compliant path forward/upward.
as always, your time and consideration are greatly appreciated.
Arthur E. Smith
artesmtih@earthlink.net