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Hi Guys,
I would like to try a modern pellet type thermostat, with the standard temperature range, for my '47 custom super (356).

Our parts x-ref for the 48-50 356 lists Napa #91 but it has a flange that is too small. Napa's online search for a '47 356 is incorrect - parts 530060 and 530080 are also too small.

Max has the pellet style, but in a high temp version.

Have any of you folks found a standard range in a pellet style?


Thanks,
Mark

How much too small? I am fairly sure the THM 91 is what I have in mine. It fits and the ring keeps it in.

Here are the specs for the 91. The flange width compares to a new bellows style thermostat from Max that I have. Flange on the bellows is 2.452 and at 2.49 the pellet spec should have it being a bit larger than the bellows. I measured the opening in the housing to be 2.490 or just under 2 1/2" and the ledge the thermostat rests against has an opening of 2 1/4 so there is 1/8 all around for the flange to seat. Ring side should be slightly larger than that but I don't have a spare to check what it compresses down to.

The 91 should be a tight fit if anything. Any chance the wrong thermostat was put in the box or has your housing eroded or rusted away somewhere?

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Howard, you are infallible....91 DOES fit. Long story, chalk this up to numbers confusion at the parts desk. I'll try and get the x-ref expanded to include 21st series 356. Napa's database is incorrect.
Thanks,
Mark

Howard rescues me on a regular basis, too!!!

There are two basic sizes for pre '70 US cars, small 2 1/8" approx and large 2 1/2" approx. All Packards 35-56 that have a cyl head t-stat use 2 1/8" except 40-50 356" which uses the large 2 1/2"

As far as the older diaphragm type restricting the flow and causing overheating, keep in mind that before the modern pellet type was invented, all cars used the former type. With 20-30 million cars on the road with the diaphragm type there were not masses of overheating cars caused by the thermostat and for sure there was no recall.

Thanks
James From
Kanter Auto Products

The bellows or diaphragm type thermostats were replaced with the capsule type when radiator pressures were increased over the no or very low pressures used until the early 50's. There are several places that go into detail explaining the theory and reasons why there were issues but Packard saw fit to include an abbreviated version in a service article and a separate tech bulletin when they made the change.https://www.packardinfo.com/xoops/html/downloads/SC/SC-VOL28NO5.pdf The bulletin we have on site is poor quality but the counselor explanation article is on page 39.