<VV> 5-speed transmission

[James Davis]

Some empirical info - The Corsa runs a 180 cu in Corvair 140 with engine
stock exhaust.  The trans is a 1964 FC 4 speed with a 3.27 transaxle, 25.5
dia tires;. that figures 3,017 rpm @  70 mph.  The engine runs 325 F
(true) @ 70 mph with the ambient temps in the low 90's.F.  The Rampside has
a 166 cuin 140 with headers, SuperTrapps and lower shrouds and
thermostats.  The trans is an early 61 4 sp (4.26:1 first gear) to a 64
diff with 3.55 gears and 26.3 tires - that figures 3,167 rpm @ 70 mph.
This truck has A/C, so we drive all summer even when temps are well over 90
degrees.  Both have stock 65-9 fans.  While the oil temp stays around 260 F
in the Corsa, the Rampiside will see 290 F with the A/C on at 70 mph.  The
Rampside does have dual folded fin oil coolers,.  The Corsa doesn't mind 25
mph head winds but the Rampside does.  It is not the cylinder head but the
oil temperature that goes up. If the oil temperature gets above 300 F, I
slow down or shift to a lower gear.
Jim Davis


On Tue, Aug 18, 2020 at 11:44 AM Cliff Tibbitts via VirtualVairs <
virtualvairs at corvair.org> wrote:

> Wowzer, I never dreamed my simple answer to a question would arouse so much
> interest.
>
> Kent, was there any empirical testing done prior to your installation?
> Just curious because I was not around when these units came out.  The
> testing would be nice to have but expensive and who would want to do it?
>
> On the other hand, seat of the pants experience counts for something as
> well.  Consider this.  These cars were built in the 60's before most of the
> present day Interstates were even built.  The national speed limit for most
> thoroughfares was 60 or 65 MPH.  Also consider that these cars were
> expected to spend most of their time running around town at speeds of 35-45
> MPH.  At those speeds the engine would have been 2000 RPMs plus or minus
> 500 depending on gear ratios.  Therefore I think again, that the cooling
> should not be a problem unless the RPMS dropped below 2000 rpm.  In which
> case, I would downshift.  I do that now with my 4 speed.
>
> Finally, and I don't have the information in front of me, but I read once
> that the cooling ability of the fan decreases above 4000 RPM so for people
> who like to drive at 75-80 on the interstate, I think a 5th gear would help
> quite a bit.
> --
>
> Cliff Tibbitts
> cliff at tibweb.com
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