The Stovebolt Site Forums The Shop Area Engine Shop thermostat

I've got a '46 Chevy 2-ton with a '53 235 in it. I have to replace the head gasket and while I'm at it, I figure I should put in a thermostat since there isn't one in there now. The question is what temperature should I put in? 160? 180? What did they use originally? I have a new aluminum radiator and it seldom get up to 180 even with a heavy load.

Ed,
I,m surprised that it Doesn,t Overheat with NO Tstat in it At All!
Un obstructed the coolant normally doesn,t stay in the block long enough to cool it(moving too fast)
steve sr.

I'd go with a 160

X2. I believe it came from the factory with a 160, at least my '38 did.

Steve Sr., I believe you meant to say....It doesn't stay in the radiator long enough to cool it. I use 180 to 190 for the heat to the carb.

moving too fast

No such thing.

At least 180.

Do you plan to ever use the heater? If so, use a 180. A 160 won't let the coolant get hot enough to produce much heater output. If your radiator is a zero pressure unit, using a 195 stat pushes the minimum temperature a little too close to the boiling point.

Yes, the system needs some kind of thermostat, or at least a restrictor disc for flow control, regardless of what some self-appointed "experts" have to say.
Jerry

The original 1953 thermostat would have been rated around 160 degrees: starting to open at around 150 degrees and fully open around 180 degrees.

4 psi radiator cap

The 1954 high-pressure 235 in my Suburban would not reach operating temperature (160 degrees) when running and sitting still and with no thermostat. This was with a cleaned block-interior and new-core original radiator.

The consensus seems to be 160. I do have a heater, but don't use it as I don't use the truck in the winter. Thanks.

Ed,

I have a '54 235 as described by Tim above, I run the 160 as I like you do not use my truck in the winter. I tried the 180 but on certain summer days it was just too hot, I have never had an overheating issue since switching to the 160.

How many psi radiator cap should we be using with these old trucks?

That's not a one size fits all question. What year? I'm not sure when Chevy started using a pressurized system but my '38 is 0 pressure and it was that way for years. Someone will come along with the specific year that Chevy went to a pressurized system. Basically you can look at your overflow. If it works through the cap it's likely a pressurized system. If it's like mine and is separate it's not. My overflow is down the radius of the upper tank, away from the neck and cap.

Cooling system pressure crept up over the years as manufacturers figured out they could install less-efficient radiators if they ran more pressure. Every pound of pressure on a cooling system raises the boiling point 3 degrees. Modern engines are built with alloys that allow for tighter clearances and higher normal temps, which requires pressurized coolant. Stovebolts operate well at temps from 160-200, so with a big enough radiator, no pressure at all would be needed. Practically, 7 PSI is a good rule of thumb for radiators capable of tolerating a little pressure. That raises the boiling point to 233 degrees at sea level, and more like 215-220 in Denver (5,000 feet elevation) and about 204 on top of Sonora Pass at 10K feet.

The tiny aluminum radiators on newer cars need 15-17 PSI, and normal operating temps of those engines are 220-240 degrees.
Jerry

This question comes up often. I think(opinion) the limiting factors are, Heater core( low pressure for stock styles up to 1955) and Radiator(same considerations) The Engine won't care much(216 and 235). If you are running a "modern" radiator, and don't use a heater(stock type) then you could run a 15 pound cap no problems. But with some 60 to 70 year old parts I would stay as low as possible. I use a 5 pound cap in the 52 1/2 ton. with the "recirculating" dealer installed heater. No problems for the last 2 years( all weather daily driver). Not the best window defroster action, but no leaks, overheats or other issues.

Thanks for the info. I installed a 7# cap on my 49 1/2 ton the other day and developed a leak in the heater core. I was able to stop the leak with Stopleak but I don't feel comfortable about leaving the 7# cap on it. I'll see if I can get a lower rated cap. Thanks again. Dave V

If the heater core leaks with a 7 lb. cap, replace it. It is on the verge of failing and using a lower pressure cap is like taking aspirin for a headache caused by a brain tumor.
Jerry

This thermostat is like nothing I have seen. Rather than drilling your own 1/8" hole to allow for steam venting, it has what they call a jiggle pin valve. It's a 1/8" hole with a little cover over it that opens when any pressure is present.

http://www.rockauto.com/en/moreinfo.php?pk=100490&cc=1442228&jsn=416

I was installing them 30 years ago.
Jerry

Well, okay.. Is there a downside to using them? I've been here for 16 years through hundreds of thermostat threads and you have never graced us with this rather interesting info. Typical, but not sure why you would deliberately keep this sort of information to yourself.

Thanks! I didn't want to tear my 53's housing down to take more pictures. This is a big deal for those backyard mechanics who have been told to drill a hole in their thermostat but are scared to do it. No need with this one. It comes in 160 and 180 and the last time I checked it was $3.30 and it's not even the premium model.

GATES 33006 - 160 degree
GATES 33008 - 180 degree
GATES 33009 - 195 degree

The Duralast brand at Autozone also has the jiggle pin for these thermostats.

15356--160 degree
15358--180 degree

Bought one of each yesterday.

Matt

It also gives credibility to those old guys who give you the advice.. "just drill a hole in there and you will be GTG!"

When manufacturers make them available, we KNOW it's not just some arbitrary mumbo jumbo. Very glad to learn about this.

I happened to be speaking to a Gates rep about a month or so ago and the subject of jiggle pins came up. I told him about the 1/8" hole in the flange suggestion that I'd read about on Stovebolt. He explained that a jiggle pin actually works like a check valve that will only allow air to pass through it, not coolant. When coolant reaches the jiggle pin under pressure, it seats against the thermostat flange to block coolant flow past the thermostat when the thermostat is closed.

Not saying that the 1/8" hole is a bad idea. Just sharing what I learned about jiggle pins from the Gates guy. I am sure that it would be cheaper for them to punch a hole through the flange instead of adding a copper jiggle pin.

Probably more than anyone ever wanted to know about jiggle pins, but thought it was worth sharing.

Matt

There is a jiggle pin in the thermostat on my '54 GMC 630.

Ed

Additional information on this can be found here:

http://forums.devestechnet.com/foru...1643-tip-of-the-week-31-for-may-1-7-2016

If anyone would share additional part numbers and sources, I will gladly add them.