I'm replacing the recently failed thermostat on my 360 motor and the flange diameter on the one everyone is trying to sell me measures 2.125 inches. I have another old one in a box that has a flange diameter of about 2.5 inches which fits perfectly in the housing. Unfortunately, I tested on my stove top and it doesn't seem to work. Not sure why I kept it. The 2.125 diameter one fits very sloppy in the housing and can actually fit inside the hole in the intake manifold! A guy at NAPA said maybe I have an "industrial" cooling setup on my truck. I never heard of that before. Oddly enough the thermostat that I pulled out had the 2.125 flange on it too and seemed to be doing just fine for the last few years. I realize that the direction of flow would be pushing the thermostat away from the engine but I don't think it's right that the flange isn't big enough to keep the thing out of the manifold. And if the thermostat wasn't aligned perfectly water could easily pass by the flange.
Napa is ordering one based on dimensions. Anyone else run into this problem?
Thanks.

 

Highboy74,
I would love to answer your question but I am not familiar with the 360 and do not want to guess just to provide a answer.
I will watch this and if no one responds, I will check with a few guys for you.
This should be an easy answer for any 360 owners.
alex

 

Usually there is a recess in the manifold or the neck to accept the T-stat. If it's in the neck, not the manifold then the gasket is to retain the T-stat from falling into the manifold. I have here in front of me a new 195 deg T-stat for a 360, Big A product #30109, it's diameter is 2.125. I have a new gasket, Says, Ford Prod V8 1965-78. The I D of the hole is 1.825.

I have never seen any T-stat set in a neck or manifold that did not have a matching recess (diameter) for the T-stat. T-stat needs to sit in that recess. A question, where is the recess, in the neck or in the manifold? IS this a stock intake manifold or like an aftermarket 4 barrel manifold? I'm thinking you may not have an original stock NECK.

 

Thank you sir.
Stock manifold. The recess is in the neck which may or not be stock. The recess in the neck is 2 1/2" in diameter so the T-stat can slide down 1/4 inch thereby letting water flow OVER the the T-stat. The gasket has stickem on it so you could line it up perfectly when you install it but I can't imagine that it would stay there. I must have the wrong neck. At any rate NAPA found one for me that fits in the recess perfectly and seems to be working just fine. The temperature gage was acting normal with the old one so maybe the flow around the T-stat was insignificant but I'm much happier that the new one fits perfectly.
Thanks again.

 

Glad you resolved. I have 3, 360's. I believe all stock. 2 in trucks running. Other, lets just say on the ground. When I should get into one, I'll remember your post and give a note here on what I find. Thank for letting us know your end result. Cap

 

F100/350 with FE engines:

1965/66 and some 1967's have a 2 1/2" diameter thermostat.

Some 1967's, 1968/76 have a 2 1/8" diameter thermostat.

The thermostat housings are also different.