Question for 71 Lt-1 T-stat housing 2128 or 660?

[Brad M.]

I just read the following in an ebay listing and was wondering if anyone could verify this. I have a 71 lt-1 which has the t-stat housing 3972128 mentioned below. I had assumed that it was replaced at some point and not original based upon the 70-72 judging guide which indicates that part number should be 3877660. Anyone have an Lt-1 which has the the 3972128 or who can otherwise determine if this is accurate or inaccurate below:

"ORIGINAL GM 3972128 HEAVY DUTY THERMOSTAT HOUSING USED WITH 1970-72 Z28 CAMARO’S AND 1970-72 LT-1 CORVETTE’S

THE GM PART NUMBER 3972128 IS CASTED THE BASE OF THE HEAVY DUTY THERMOSTAT HOUSING WHICH USES A THICKER AND MORE SOLID BASE WITH ONLY ONE RECESSED AREA AT THE BOTTOM OF THE MOUNTING LOCATION FOR THE LONG BOLT

THE 3877660 IS ALWAYS INCORRECTLY LISTED FOR THE 1970-72 Z28 CAMARO AND LT-1 CORVETTE WHICH WAS USED ON STANDARD V-8 CAMARO’S OR SS 350 AND SS 396 CAMARO’S

THE 3877660 WATER NECK WAS USED ON MOST CHEVROLET V-8’S AND LISTED AS A REPLACEMENT FOR ALL V8’S IN THE CHEVROLET PARTS CATALOG’S

THIS SPECIAL HEAVY DUTY 3972128 THERMOSTAT HOUSING USED ON THE 1970-72 LT-1 CORVETTE’S AND Z28 CAMARO’S WAS ONLY USED ON THE ASSEMBLY LINE AND WAS NOT AVAILABLE AS A SERVICE PART MAKING THIS WATER NECK A VERY

DIFFICULT PART TO FIND

THE ASSEMBLY MANUALS DO NOT SHOW THE THERMOSTAT HOUSING PART NUMBERS FOR THE LT-1 CORVETTE OR Z28 CAMARO AND THE ONLY WAY TO VERIFY THE 3972128 USAGE ON THE 1970-72 LT-1 CORVETTE’S AND Z28 CAMARO’S IS FROM ORIGINAL LT-1 CORVETTE’S AND Z28 CAMARO’S RETAINING THEIR ORIGINAL THERMOSTAT HOUSING’S"

[Robert E.]

Re: Question for 71 Lt-1 T-stat housing 2128 or 66

Brad,

I just went out and checked my '71 LT-1 and it does have housing #3877660. I was just thumbing through the Judging guide and can't find a reference to the housing numbers. What page is that on?

Robert
41801

[Joe L.]

Re: Question for 71 Lt-1 T-stat housing 2128 or 66

Brad------

The GM #3972128 thermostat housing was used ALTERNATELY to the 3877660 during the 70-73 period. It is NOT a "heavy duty" thermostat housing and it was certainly not used exclusively for LT-1's. They can be found on many engines during the period described. However, they will not be found on any engine which requires the triangular "tab" with a hole in it as the anchor point for the accelerator return spring. Actually, I think that there were few, if any, applications that required this "tab" during the 70-73 period. The "tab" is the only functional difference between the 3972128 and the 3877660, although there are a few other minor configuration differences.

In my opinion, either of these thermostat housings should be considered correct for any 70-73 Corvette.

The seller would probably like to THINK that this is a rare and necessary piece so that it will command more money or inspire foolish bidders to pay foolish prices.

The seller is correct that the 3972128 was never available in SERVICE; it was a PRODUCTION-only piece. So, he did get that part right.

[Terry M.]

Re: Question for 71 Lt-1 T-stat housing 2128 or 66

Brad,

Thanks for asking the question. While this information does not directly apply to your 1971 question, I think it will shed enough light on your question that you can evaluate the eBay sale and the seller’s statements.

The 1972 Flint build sheets for the water outlet state:

"3877660 Alum. has tab

OPT.
3972128 Alum. no tab

1- 3932368 Stud R-H 3/8" 5/8" Long"

The sheet lists the suffix codes to which these instructions apply. There are a total of 30 car engines listed, among them ALL Corvette 350 CID engines for 1972.

FWIW – 35 small block truck engines for 1971 have the same water outlet note -- less the stud listing.

What can one conclude from this information:
1) The 128 outlet is an optional outlet
2) Tab or no tab was the major difference

We are left to speculate if the water outlet build sheets for 1970 or 1971 were any different, but my money would be that they are not.

I wish I would have researched this when the latest 1970-72 TIM&JG was being written. Now you know why the judging manuals will never be without revisions.

[Brad M.]

Re: Thanks for responses/info

I had previously thought that my car must have a non-original t-stat housing on it. Based upon the information that it was apparently used on some 71 corvettes (whether Lt-1 or not) and that this 2128 housing was not available as a service replacement item, I think that I will keep it on there and basically assume that it is original to my car.

Thanks again, Brad

[Mike E.]

Re: Thanks for responses/info

My 71 LT-1 (30K miles, original belts, hoses, clamps, etc.) is 148 cars from the end of production. It has a 660 housing.

[Phil P.]

Re: Thanks for responses/info

this was covered about 6 mos ago---inconclusive results---my org heavy doc 72 lt1 has a 128 on it---wait for a judging manual then lets do what ever

[Alan T.]

Re: Thanks for responses/info

You are wise to keep it on there, Brad. My original (Star for Mechanical in Bowtie judging) very late 1970 LT-1 has the 660 housing on it, but it is not the original off-the-line housing for the car - the original 128 housing, along with the original hose, had been taken off years before by a former owner because a judge said they were incorrect. Fortunately that owner had saved the original housing/hose and later gave it to me, stating that for sure it was the one the car left the factory with. Also, the GM number on this saved original hose (still mounted to the original 128 housing) was different than what was called for in the JG - but the original-owner '70 LT-1 next to mine at Bowtie judging had the same hose number (it was a 5-Star Bowtie car). I had hoped at the time that the Bowtie team leader would have shown more interest..

[Harmon C.]

Re: Thanks for responses/info

The housing #128 was used on most all 73's I have looked at and was changed to read that way in the 73 TI&JG. The 660 was used for many years and the information just was put in later manuals and soon it makes people change out original parts to match the book.

Lyle

[Robert P.]

Re: Thanks for responses/info

A friend of mine has a early 71 LT1,he purchased new, It has the # 128 housing. Bob