First of all some facts from a Stant technical person: They
made the OEM stat for the LT5; the reason there is a rubber seal
on the thermostat valve is to minimize coolant leakage, and
thereby promote a faster warm-up; all the rubber parts in the
OEM thermostat are subject to deterioration and this may change
how the stat performs over time. The thermostat valve spring is
there to close the valve; and because the LT5 Stat has coolant
flow in reverse [Re: the stat] the spring is engineered to take
into account that coolant flow effect [flow tends to open the
valve].
Now noting that many thermostats seem to have similar
construction, I found a Stant # 29306 at Pep Boys [$2.99] that
is a 160F stat and has a flange diameter of 54MM. It has a metal
to metal thermostat valve. This flange can be reduced to 44mm
quite easily with a high speed grinder followed up with a file;
this is made even more easy by the fact that the stat has a
pressed in circumferential ring at very close to 44mm. The fact
that the valve spring is engineered for flow in the other
direction is a consideration, but may turn out to be
insignificant.
Relative to the coolant bypass valve of the OEM stat: if the
application had an after-market all-alluminum radiator, it may
be that a bypass valve would be unnecessary. A cylindrical
aluminum plug with about (3) 1/8" holes could be clamped into
the bypass hose as a substitute.
For stock radiator cars, the reduced flange diameter # 29306
stat can have an OEM equivalent bypass valve attached to it. The
way I did it was to take a Stant #35399 [$4.79 @ Krager] stat. I
then removed the bypass valve assembly [with a 1/4" pin punch].
I then disassembled the bypass valve to salvage the tubular two
diameter part that presses on to the "heat engine" pellet
chamber. This fixture allows for a lot of innovation as to how
to "create" an OEM equivalent bypass valve. I shortened the
small tube end to about 3/8" length. I found that the stainless
steel tubing from a set of TV rabbit ears had a diameter that
would press fit into the above mentioned fixture. Once "pressed
in", the length can be cut with a mini tubing cutter to equal
spread of the OEM stat flange to bypass valve measurement. Then
one has to create a stop for the valve at the end of the tube. I
used ACE hardware # 2014397 rivet [expanded with an allen
wrench] resulting in an 8-32 thread fixed at the end of the
tube. I then modified a stainless steel flat fender washer to
the equivalent of the OEM valve, and created a stop with an 8-32
SS allen head screw with an appropriate stop washer. I found a
spring that worked as equivalent to OEM with no modification
[#37 at ACE Hardware]. All relevant surfaces were cleaned with
alcohol and then the allen screw was locked into the rivet with
Locktite Weld and likewise the large end of the attachment
cylindrical device [from #2930 stat] to the copper pellet
chamber....verifying that it was concentric before the "weld"
set up.
The SS bypass valve to SS shaft may be superior to OEM. The fact
that there is no rubber rim around the thermostat valve may make
this hybrid more durable.
Note: Randy Woods has made and is offering for sale: 145,
160, 170 F thermostats.
Take a look at his website:
http://www.zr1products.com
