1972 LT-1 Thermostat: What is correct?

[Anthony F.]

I think the thermostat in my 72 LT-1 may have 'failed open' (sill diagnosing), so I'm looking into a replacement. The thermostat has been replaced a few times over the years, I didn't know enough at the time to keep the original. The last time it was replaced, I used a 170 degree, based on what I thought was correct. But I did some additional research, so I am confused.

My 1972 Chevrolet Passenger Car Service Manual states that I should be using a 195 degree. I checked several GM parts catalogs on GM Wiki (see below, from a 1979 catalog), it shows that all 70 through 74 should be using a 170 (PN 3033780). I also checked the 'Corvette Specifications' info I downloaded from the GM Heritage center (Revised September 1971), that shows in two places the LT-1 is using a thermostat that 'begins to open/full opened at' at a lower temp than the base engine or 454, but doesn't specify an actual thermostat by degrees (see below). I couldn't find anything in the 72 AIM. I also searched for prior NCRS posts, I couldn't find a post on this subject.

Any opinions on what I should use (170, 180, or 195)? It runs fine with the 170.

[Mike F.]

Re: 1972 LT-1 Thermostat: What is correct?

My guess on the temperature ranges in your above pics is,

192*-198* = 195* Base/454
177*-183* = 180* LT-1

[Joe L.]

Re: 1972 LT-1 Thermostat: What is correct?

I think the thermostat in my 72 LT-1 may have 'failed open' (sill diagnosing), so I'm looking into a replacement. The thermostat has been replaced a few times over the years, I didn't know enough at the time to keep the original. The last time it was replaced, I used a 170 degree, based on what I thought was correct. But I did some additional research, so I am confused.

My 1972 Chevrolet Passenger Car Service Manual states that I should be using a 195 degree. I checked several GM parts catalogs on GM Wiki (see below, from a 1979 catalog), it shows that all 70 through 74 should be using a 170 (PN 3033780). I also checked the 'Corvette Specifications' info I downloaded from the GM Heritage center (Revised September 1971), that shows in two places the LT-1 is using a thermostat that 'begins to open/full opened at' at a lower temp than the base engine or 454, but doesn't specify an actual thermostat by degrees (see below). I couldn't find anything in the 72 AIM. I also searched for prior NCRS posts, I couldn't find a post on this subject.

Any opinions on what I should use (170, 180, or 195)? It runs fine with the 170.

Anthony------


All Chevrolet engines of the period that were equipped with AIR emissions control systems (which includes ALL LT-1's) were originally equipped with a 195 degree thermostat. All other engines were equipped with a 180 degree thermostat. I recommend a 180 degree thermostat for all applications, including those originally equipped with a 195 degree thermostat.

[Joe L.]

Re: 1972 LT-1 Thermostat: What is correct?

By the way, the information in your post originated from the Automobile Manufacturer's Specifications and is yet another example of how those specifications are often inaccurate. They've got the thermostat information REVERSED.

[Anthony F.]

Re: 1972 LT-1 Thermostat: What is correct?

Thanks Joe,

I will go with the 180 degree.

I had all the original components for the AIR system rebuilt a few years ago, but haven't reinstalled them. I'm still a few years away from considering having my car judged.