Motor, Mopar Thermostat Housings

Well this is my first thread. Hope you enjoy.

I would like to share some of the information I found out about Mopar thermostat housings and thermostats while checking fitment of a product I make. Some of this information is easy to find but some of it I really had to dig to find. To the best of my knowledge this information is correct and accurate. Please feel free to add to the information, clarify or correct any errors. Also if anyone has pictures that they would like to add that would help clarify any of the information please do so.

First I would like to point out that thermostats are sometimes referred to as a T-stats. Thermostat housings can also be called T-stat housings, water necks or water outlets. It helps to know this when doing searches on forums or at online auto parts stores.
Here are the basics. There are essentially two different water outlet bolt patterns used by all Chrysler engines from 1924-2003 . One is the older large size with a center to center bolt pattern of 3.25 inches. This pattern was used on all v8 engines from 1951 to 1978 and all flathead 4, 6 & 8 inline engines back to 1924. The thermostat diameter is 2.49 inches for this size housing. The other water outlet bolt pattern is 2.875 inches. This pattern was used on all slant 6 engines and the newer small block engines made after 1978. The thermostat diameter is 2.125 inches for this size housing. All flathead 4, 6, 8 inline, Slant 6 and V8s made before 1979 use 3/8 inch bolts. V8 Small block engines 1979 and newer use 5/16 inch or metric size bolts.
Things get more complicated. Even though the 3.25 pattern is the same for all v8s from 1951-1978 many of the 1950s water outlets have bypasses built into the housing. This is also true of most of the flathead 6 & 8 inline engines. If you plan to change to a different water outlet on these engines it is important to know what the bypass did and is changing to a non bypass water outlet going to have an adverse effect. Bypasses are used on these engines mostly to keep from having hot spots in the cooling jacket as the engine comes up to temperature because the bypass recirculates the water in the engine. They are also used were the winter temperatures are very cold so the heater warms up faster. In addition some of the thermostats were constructed to work in conjunction with the water outlet’s bypass and use a different size Thermostat. Most of these thermostats are 2.55 inches. Some of the small block v8 aftermarket manifolds have both the 2.875 and the 3.25 bolt patterns which allow you to use either size water outlet. Also not all water outlets use the same size radiator hose.

Can you use Chevy water outlets on a Mopar? The 3.25 inch bolt pattern is also the same as the Chevy v8s and they can be made to work on a Mopar engine. However it should be noted that the recess for the thermostat on Mopar engines is in the water outlet and Chevys are in the intake manifold so using a Chevy water outlet on a Mopar is not a slam dunk. In addition the housing of the Chevy is about 1/4 inch smaller diameter so it doesn’t cover all of the mounting area and looks a little odd. The thermostat size used by Chevy is the same as used with the slant 6 and 1979 and newer small block v8s.

 

Welcome, and a great thread! (I thought I was the only one that researched lines of possibles when discovering I might have the wrong T-stat housing on a job I was doing...)

Your research is noted, (I have Hemis and this info is quite handy) I also have numerous other projects in the works...

Thanks for your research.

 

Your info appears correct. I have a 318 Dodge poly of 63 vintage and the thermostat is stamped 63mm which according to my calcs is 2.48" and the setscrews holing it are 3/8"

I did notice last night when searching for a T-stat housing gasket that there were various sizes in the Felpro engine rebuild kit which I guess suit the later family of engines.
Do you have a preference for the stamped steel gasket instead of the composite material. I prefer the composite as it doesn't rust.

 

I have not used the Stamped steel gaskets. I only use composite or o-rings depending on the application. The stamped steel should be ok if your coolant is properly maintained and the water you dilute it with is distilled and not just out of a hose.

 

I am finishing up a 51-52 Dodge Flathead in an old Forklift. I broke the edge of the original water neck. I had a Chevy 350 housing laying around and I used a Chevy 350 thermostat.

 

Very nice. Did you have to modify the water neck so the thermostat would register in it?

 

I did not make any modification. The thermostat sits in the recess in the neck. The gasket came with the rebuild kit for the engine. It seems pretty ridged with a metal ring. Without the gasket the thermostat is right up to the edge of the opening so I don't think it's going anywhere. I did put a water gauge on the fork truck so I can keep an eye on it but as of right now it look like a bolt on hands off change.

 

Swifty........that stamped steel gasket is for the exhaust manifold/engine pipe connection.......lol........... you should know that.........lol........regards, andyd(a fellow poly tragic)

 

DOH! well that explains why there was 2 of the stamped steel ones and only one composite one in my gaskets left over from the engine build. Thermostat housing must be similar shape and bolt circle to the manifold exhaust flange.
I never use the stamped steel gaskets, always make my own out of wire re-inforced composite material for both inlet and exhaust manifolds.

 

I bought a Dodge thermostat housing off of eBay for our '56 Dodge 315V8 Poly and when I got it, it has 3 small pin holes in the neck where the hose clamps on. Can it be repaired with jb weld or something else? I seem to have had a hard time finding anyone willing to part with a decent one.

Jay

 

I have had some success with using JB weld on stuff like that. The one thing that will make a big difference is make sure the part is clean and free from any rust. I would sandblast it first. Then clean it with lacquer thinner or alcohol and let it dry good before applying the JB weld or what ever you decide to use. If the holes are only under the hose area you may be able to use some type of liquid rubber that would set up.

Can you use a different housing or does it have to be a 56?

 

I think '55 and '57's are the same. Just so it points forward and upwards towards the radiator. There may be other years that will work, but, I don't know which ones.

 

You may be able to get a NOS one from http://www.bradsnosparts.com or
http://www.mmpar.com They both have a lot of NOS parts. I think some of the non A/C ones are the same up to 66.

 

Here are a couple shots of my brothers 51 Ply. It has a 55 Chevy radiator. The Cool-View and water outlet is a direct bolt on. No mods required.