I had a ride in a 1942 Chev Canadian Military Pattern truck this weekend and at one point during a rough off road ride the driver openned a small door in the dog house engine cover...."to open the valve that releases the steam in the back of the 216 head"..... just been flabergasted!!!

At the back of the head....where the mechanical water heat sensor fit to the head ..... it seems the head has a large brass adapter with a T fitting and valve which is connected to the top of the expansion tank of the rad..... once opened it vents to the tank/rad and allows for more even cooling of the engine...... on top of the adaptor the mechanical sensor is treaded in the brass fitting.....

How critical is that plumbing???? has any civilian 216 or later 235 ..261 ever had that special venting arrangement???

I am installing a 261 in a 1940 military truck and wonder if I will need such a connection....
All the 1958 GM shop manuals make no such reference......

Would it be only for very severe service such as climbing/decending very steep hills under load????

I was amazed at what the old 216 could do...it lead the convoy in muddy roads and more modern equipment got stuck behind him.... got hi-centered once but someone remarked that only 2 wheels were spinning.... red faced the driver had forgotten to engage the 4x4 drive..... slow has hell but it got there.....

So how strange-weird is that steam valve????

Bob C.

Bob C.
CMP Heaven
The Hammond Barn