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June 22, 2005
Paul....
"Thin flange" refers to the thickness of the
actual wall of the block, this thickness being
most apparent in the block's lower "flange" which borders the oil sump.
As far as I know, the company went to thicker wall ("thick flange") 1275's
by '68.
For stock bores, the thin-flange was not a
weak engine. I tested a Judson blower on a
stock bore thin-flange '67 for many, many
runs at 4-6psi to 6,000rpm and while we did not retain the blower, there wa
s no apparent engine damage as the motor continued to run just fine for man
y miles
after the blower was removed until the
vehicle's ulitimate demise at the hands of
a rather large truck!! :)
The EN40B came stock in these "early" Sprite 1275's as I understand it, alo
ng with
the Cooper "S" mechanical advance (only)
dizzies. As I understand it, the factory went
to the EN16T (truftrided) crank and a 25D
(combo mech/vac advance) dizzy as they
transitioned to the "later" thick-flange
blocks.
However, you can bet the factory didn't throw away any parts for the sake o
f
uniformity in engine construction. I'm quite
sure they used whatever they had handily
available to keep production going as they
made the transition of "thin" to "thick"
walled motors.
No doubt there are some thin flanged 1275's with EN16 or EN16T cranks and
vice versa with respect to the EN40B. Same
with the 23D vs 25D dizzies I suspect as well,
along with other parts.
And BTW, according to Bill Perry
not all EN16 cranks were of the
"T" variety, though they were supposed to
have been. He states he's taken apart quite
a few thick flange blocks and found the crank to be EN16 only.
Dunno how many 1275 "inline" EN40B's are
floating around. According to Bill Perry, not
many. At least he hasn't seen a lot of them in his Big Bore A-Series commer
cial engine
building experience.
Cap't Bob
Basic Frog
"Robert E. Shlafer" < PilotRob@... > 37641
Posted on June 22, 2005 08:20 PM
Posted to category(s) Engine (external) | Engine (internal) | Gauges | Ignition System | Lubrication System | Miscellaneous | Restoration | Tuning | US States
