73 thermostat housing

[William M.]

Judging Manual calls for part # 336790 on L48/L82 and part # 336773 on LS4. I have a LS4 with part # 397212 - anyone know what application this was used for?

[Joe L.]

Re: 73 thermostat housing

Judging Manual calls for part # 336790 on L48/L82 and part # 336773 on LS4. I have a LS4 with part # 397212 - anyone know what application this was used for?

William-----


I'm unfamiliar with the configuration of either the 336773 or the 397212. Plus, I don't understand why either of those would have been used on a 1973 LS-4, but I'm NOT saying they were not. The GM #336773 was a thermostat outlet once available in SERVICE, but I cannot find that it was ever cataloged for a Corvette. That does not mean that it wasn't so-used, though. GM #397212 was never available in SERVICE and I have not otherwise been able to determine an application.

The thing that surprise me is that the GM #336790 is shown for 1973 L-48/L-82 applications. My recollection is that the 336790 has fittings for temperature switches on it and I don't recall any thermostat housing-mounted temperature switches being used for the 1973 model year.

[Sal C.]

Re: 73 thermostat housing

William, I believe the number you are refering to is actually 3972128. This number has been seen, although rarely, on some original 1970 to 1972 Corvettes. It is more often seen on the 1973 LS4. The '128 outlet is of a much stronger design and has an "O-ring" cast into the intake manifold mating surface for a more positive seal. I don't believe this number was ever available over the counter, assembly line only.

[William M.]

Re: 73 thermostat housing

William, I believe the number you are refering to is actually 3972128. This number has been seen, although rarely, on some original 1970 to 1972 Corvettes. It is more often seen on the 1973 LS4. The '128 outlet is of a much stronger design and has an "O-ring" cast into the intake manifold mating surface for a more positive seal. I don't believe this number was ever available over the counter, assembly line only.

I don't see an "8" at the end. The "397212" is fairly well defined. I guess it's possible the "8" isn't raised as much as the other #'s and there is a good amount of paint on the housing. It sure looks old and original. I think I'll leave it alone and see what the judges say this Sunday.

[Harmon C.]

Re: 73 thermostat housing

William
The 3972128 is the correct thermostat housing for all 73's this is well known but the change missed getting in the manual. I got a deduction for this part number in Mars PA. at a regional. When I got home I checked the five 73's I had at the time and all of them including the 454 had the 3972128. I had been buying 336790's at swap meets for extras and they do not have a threaded hole for a fitting. This is an example of how things installed on the cars were not like what the books said.

[Todd L.]

Re: 73 thermostat housing

Lyle,

Should I stop my quest for 336773 thermostat housing and start looking for a 3972128 number for my 74 LS4? Or did you buy them all up?
Do the manuals get supplements added instead of reprinting a new book? I have a second edition with updates for the 73-74. Is this the most current?

Thanks

Todd

[Harmon C.]

Re: 73 thermostat housing

Todd
If you have a manual with updates you could have some information I do not have as I have just the 73-74 second edition. I only did my research to get the 73 housing changed to 3972128. I have a picture of a 74-454 with very low miles and the housing on it has a sender in the top with two vacumn ports. I do not have a part number.

[Joe L.]

Re: 73 thermostat housing

William
The 3972128 is the correct thermostat housing for all 73's this is well known but the change missed getting in the manual. I got a deduction for this part number in Mars PA. at a regional. When I got home I checked the five 73's I had at the time and all of them including the 454 had the 3972128. I had been buying 336790's at swap meets for extras and they do not have a threaded hole for a fitting. This is an example of how things installed on the cars were not like what the books said.

Lyle----

The GM #3972128 was a PRODUCTION-only thermostat housing. It is seen occasionally on 70-72's and its part number implies a 1970 release. I did not realize that this housing was used for all 1973's but it's certainly of a configuration that would be suitable for 1973's. The only difference that I THOUGHT existed between the 3877660 and the 3972128 was a slight difference in the configuration of the base and the lack of a throttle return spring anchor on the 3972128. Sal's information is quite interesting. I did not know that the 3972128 was used in conjunction with an o-ring rather than a gasket. Attached is a photo of a 3972128.

Do you have a photo of the 336790 that you can post?. I have an NOS example here but I hate to have to dig it out. My very strong recollection, though, is that it has 2 NPT fittings on it. Plus, it was supposed to have been used for 1974-77. To have been used for those years, it would have to have 2 fittings.

[Joe L.]

Re: 73 thermostat housing

Lyle----

The GM #3972128 was a PRODUCTION-only thermostat housing. It is seen occasionally on 70-72's and its part number implies a 1970 release. I did not realize that this housing was used for all 1973's but it's certainly of a configuration that would be suitable for 1973's. The only difference that I THOUGHT existed between the 3877660 and the 3972128 was a slight difference in the configuration of the base and the lack of a throttle return spring anchor on the 3972128. Sal's information is quite interesting. I did not know that the 3972128 was used in conjunction with an o-ring rather than a gasket. Attached is a photo of a 3972128.

Do you have a photo of the 336790 that you can post?. I have an NOS example here but I hate to have to dig it out. My very strong recollection, though, is that it has 2 NPT fittings on it. Plus, it was supposed to have been used for 1974-77. To have been used for those years, it would have to have 2 fittings.

The photo didn't get attached to my last post, but here it is since I can't seem to add it to that post.

[Harmon C.]

Re: 73 thermostat housing

The GM #3972128 that was used in 73 had a regular gasket not an O-ring.The 336790's I had were not taped for any fittings. I may have sold them when I found out they were not 73 parts but I will take a look.

[Sal C.]

Re: 73 thermostat housing

Joe and Lyle, I didn't mean to imply that it used a o-ring in place of the standard gasket. There is, however, a raised ring cast into the mating surface that helps make for a more effective seal.

[Joe L.]

Re: 73 thermostat housing

Joe and Lyle, I didn't mean to imply that it used a o-ring in place of the standard gasket. There is, however, a raised ring cast into the mating surface that helps make for a more effective seal.

Sal-----


OK, now I know what you mean. I think the later SERVICE versions of the 3877660 (the ones that lacked the "depressions" in the base section) also came to incorporate that feature.

[William M.]

Re: 73 thermostat housing

The photo didn't get attached to my last post, but here it is since I can't seem to add it to that post.

That's the one that I have. Thanks, now I've got one less thing to replace before the car is judged this Sunday!

[Roger S.]

Re: 73 thermostat housing



I went and checked my '73's T-H and it had P/N 3877660 on it - see picture. It has depressions on the base and when I changed the thermostat it used a gasket - not an o-ring. Per Joe L's post I should now be on the look out for another since this is not an original part but a service replacement.

Roger

[Joe L.]

Re: 73 thermostat housing

I went and checked my '73's T-H and it had P/N 3877660 on it - see picture. It has depressions on the base and when I changed the thermostat it used a gasket - not an o-ring. Per Joe L's post I should now be on the look out for another since this is not an original part but a service replacement.

Roger

Roger-----


I don't really think this is a SERVICE replacement. If it is, it's a very old replacement since this style housing and part number was changed in minor ways in later SERVICE.

Frankly, I can see no reason why the GM #3877660 and the 3972128 could not have been used interchangeably in PRODUCTION. The only functional difference between the two is the presence or absence of the accelerator return spring anchor point. This is totally irrelevant for a Corvette engine.