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July 08, 2005
You building a "Town/Country" or "Highway" driver, Bruce?
ALL ELSE BEING EQUAL.....
"60"overbore will pull up low end torque
(increases compression ratio) whilst increasing "revability"
(more "square" bore/stroke numbers)
As can be seen, the foregoing improvement lends itself automatically to
a "hairier" cam quite nicely (without
compromising the low end).
The question is "how hairy" for your specific application? Thus, the initi
al question at the top of the page, Bruce.
Vizard's book contains an excellent description of many "grinds".
For town/country, the numbers
associated with an MD266
give a nice general improvement all-around with slight emphasis on mid-rang
e/top end using CR's
between 9.0/10.0-1 (maybe a little higher
with aluminum head) which is compatible
with today's garbage unleaded premium
octanes.
The Kent 276 gives beefier mid-range/top
end but the "60" overbore should prevent
undue low end loss. Change to an AH1 needle and "red" spring with the stock
induction set-up will see you through.
In highway work wherein good high end
response/cruise is favored, those numbers
associated with a Kent 286 or Vizard (SP)
VP3 are useful (min CR about 9.5-1) with
AH2 needles (or thereabouts) "red" springs.
The numbers associated with the latter, immediately foregoing grinds are ab
out
as far as you can go for the road, without
unreasonably compromising low end "traffic" tractability.
In all cases and most especially so with the hairier cams, a larger intake
valve and larger diameter free-flow exhaust system
are beneficial along with increased inducted air capacity, of course.
Higher compression ratios with the latter
grinds would be very beneficial with respect
to NOT compromising low end with these
hairier cams, but on today's garbage octanes you begin to run into a "dead
man's" zone with respect to ignition advance rates in terms of pre-ignition
/detonation which inevitably compromises engine service life....PITA!! :):)
Cap'n Bob
Basic (albeit mildly tuned:) Frog
"Robert E. Shlafer" < PilotRob@... > 37801
Posted on July 8, 2005 01:21 PM
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