Deve,

Does that thermostat have a 2.125" diameter?

I'll measure my 261 thermostats tomorrow.

The 1960 Shop Manual show the following 261 thermostat: Dole DV-50 (Dole Pellet Bypass - supposedly also the Harrison T180 thermostat).

It looks like the by-pass was a part of the thermostat?

http://www.google.com/patents/US3157357

" . . . a thermostat valve arrangement including a valve casing adapted to be mounted in a two-way housing for conducting fluid, a main valve being adapted to control flow through one way leading through the housing and a movable portion of a pellet-type motor being arranged not only to operate the main valve but also to control fluid flow through the second way leading through the housing . . "

This style thermostat started being used by GM in the 283 (and in later 261) engines.

Last edited by tclederman; 03/15/2016 1:32 AM.
Tim
1954Advance-Design.com
1954 3106 Carryall Suburban
1954 3104 5-window pickup w/Hydra-Matic
The 216 and early 235 engines are not "splash oilers" -- this is a splash oiler.