What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

[Tom S.]

I am looking for the correct original water pump 3/4 inch heater hose fitting for the 1971 LT1 small block 350 without AC. I have attached a photo of the fitting that I have and it has two "nicks" on the edges going around the fitting. I have seen others that have only one "nick" going around the edges on fitting. Which one is correct as original? Any comments would be welcome. Thanks

[Terry M.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Does anyone have an idea, other than a SWAG, as to what those "nicks" mean; or why they are there?? Asking for a friend.

[Joe L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Does anyone have an idea, other than a SWAG, as to what those "nicks" mean; or why they are there?? Asking for a friend.

Terry-----


I believe they identify the manufacturer of the fitting. I don't know how to decode it, though, and at this point it's entirely academic and a moot point.

[Gary B.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

My 1971 parts book calls for a 38499848..
It should look like this.
Gary B
3849848.jpg

[David L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Attached is a photo of a 3736495 nipple for a 3/4" heater hose and described in my 1969 Chevrolet Parts catalogs (Oct. 1968 & May 1969) in Gr. 8.866 as "2 3/4" O.L. X 7/8 hex. - 1/2-14 thrds." The length of the threads measure about 0.69" long. The length of the hex section measures 7/8" long. This one does not have any "nicks". I may have others in my 40-year collection.
GM # 3736495 was replaced by GM # 3849848 in June 1971 as per my Chevrolet Parts History manual for "over the counter" parts.
Dave

[Terry M.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Terry-----


I believe they identify the manufacturer of the fitting. I don't know how to decode it, though, and at this point it's entirely academic and a moot point.

Joe
That was my SWAG as well. I have seen them with one "nick" nearer the center of the hex portion.

[Joe L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Attached is a photo of a 3736495 nipple for a 3/4" heater hose and described in my 1969 Chevrolet Parts catalogs (Oct. 1968 & May 1969) in Gr. 8.866 as "2 3/4" O.L. X 7/8 hex. - 1/2-14 thrds." The length of the threads measure about 0.69" long. The length of the hex section measures 7/8" long. This one does not have any "nicks". I may have others in my 40-year collection.
GM # 3736495 was replaced by GM # 3849848 in June 1971 as per my Chevrolet Parts History manual for "over the counter" parts.
Dave

Dave------

The GM #3736495 nipple was discontinued from Chevrolet parts in June, 1971 and replaced by the GM #3849848 as you mention. However, it continued to be carried by GM for other car divisions until October, 1986 when it was finally discontinued and replaced by the 3849848.

As far as the correct nipples go, the 3736495 was used for all small blocks and big blocks without C-60 through at least early 1968. Thereafter, it may or may not have been used for non C-60 small blocks and big blocks. My original owner, non-C-60 small block was equipped with the 3736495. It could be that the 3736495 and 3849848 were used interchangeably. Both are virtually the same length, the same thread size and really differ only with respect to the length of the hex.

Small blocks with C-60 used nipple 3849848 from 1964 right through the end of C3 production. Why this nipple, introduced in late 1963 calendar year, was used instead of the 3736495 I do not know. All I can presume is that there was some feeling on the part of the designers that the long hex of the 3736495 would somehow interfere with some of the C-60 components.

1966-74 big blocks with C-60 used nipple GM #3739798. This is a much shorter nipple.

[David L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Dave------

The GM #3736495 nipple was discontinued from Chevrolet parts in June, 1971 and replaced by the GM #3849848 as you mention. However, it continued to be carried by GM for other car divisions until October, 1986 when it was finally discontinued and replaced by the 3849848.

As far as the correct nipples go, the 3736495 was used for all small blocks and big blocks without C-60 through at least early 1968. Thereafter, it may or may not have been used for non C-60 small blocks and big blocks. My original owner, non-C-60 small block was equipped with the 3736495. It could be that the 3736495 and 3849848 were used interchangeably. Both are virtually the same length, the same thread size and really differ only with respect to the length of the hex.

Small blocks with C-60 used nipple 3849848 from 1964 right through the end of C3 production. Why this nipple, introduced in late 1963 calendar year, was used instead of the 3736495 I do not know. All I can presume is that there was some feeling on the part of the designers that the long hex of the 3736495 would somehow interfere with some of the C-60 components.

1966-74 big blocks with C-60 used nipple GM #3739798. This is a much shorter nipple.

Joe,
The 3736495 nipple (2 3/4" long) in my photo was removed from a water pump with casting # "3927170" and casting date "A 18 70" (Jan. 18, 1970). This water pump was used on engine blocks used in 1970 Camaro SS350 models as well as other 307 & 350 C.I. engines that were cast in Tonawanda, NY. Tonawanda used the 2-digit year on their casting dates. My 1970 Camaro Assembly Manual (UPC 1, Sheet M5) lists the water pump nipple as GM # 3739798 for V8 engines. GM # 3739798 is the short nipple (1 1/2" long) used with 3/4" hoses. According to my Chevrolet Parts History Manual GM # 3739798 was replaced by GM # 3736495 in May 1966 for service parts (not necessarily assembley line parts). This is what I am confused about. I can see why the 1 1/2" long nipple might be used with models with A.C. for possible clearance issues. I have other 2 3/4" long nipples in my collection but I never really paid much attention to what engines I removed them from in the salvage yards...... I guess that I should have.
Dave

[Joe L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Joe,
The 3736495 nipple (2 3/4" long) in my photo was removed from a water pump with casting # "3927170" and casting date "A 18 70" (Jan. 18, 1970). This water pump was used on engine blocks used in 1970 Camaro SS350 models as well as other 307 & 350 C.I. engines that were cast in Tonawanda, NY. Tonawanda used the 2-digit year on their casting dates. My 1970 Camaro Assembly Manual (UPC 1, Sheet M5) lists the water pump nipple as GM # 3739798 for V8 engines. GM # 3739798 is the short nipple (1 1/2" long) used with 3/4" hoses. According to my Chevrolet Parts History Manual GM # 3739798 was replaced by GM # 3736495 in May 1966 for service parts (not necessarily assembley line parts). This is what I am confused about. I can see why the 1 1/2" long nipple might be used with models with A.C. for possible clearance issues. I have other 2 3/4" long nipples in my collection but I never really paid much attention to what engines I removed them from in the salvage yards...... I guess that I should have.
Dave

Dave-----


The story on the GM #3739798 nipple is about the same as what I previously mentioned for the GM #3736495. The 3739798 was discontinued from Chevrolet SERVICE parts in May, 1966 and replaced by the 3736495 as you mention. However, it lived on in SERVICE for other GM car divisions and was finally discontinued from SERVICE without supersession only a few years ago. As I also previously mentioned, it was used in PRODUCTION for BB Corvettes with C-60 right through 1974.

I believe that for 1969 and later Corvette engines, the waterpump hose nipple was installed at the engine plants for at least some, if not all, engines. So, it's hard to come up with any documentation as to what part number(s) were used. Therefore, we have to rely on what is observed on known-original cars. As I mentioned, my original 1969 small block was originally equipped with the 3736495 nipple. I believe that nipple could have been used well after 1969 for non C-60 SB and BB Corvette applications.

[Patrick H.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Joe,

A question on the C60 usage.
In 1972 they started to install this part at the engine plant rather than at St Louis, as 72 and later it's now painted engine color. In addition, the engines were not coded for C60 vs non-C60.
So, my thought is that they could not have been using two different parts since Flint had no idea if the end car would or would not have C60.

Does that sound correct?

Patrick

[Gary B.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

After all is said and done, attached picture is from a very low mileage 71 LT-1. Engine build date of Feb 3rd, 1971.
Gary Bosselman
DSCN5656.jpg

[Joe L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

Joe,

A question on the C60 usage.
In 1972 they started to install this part at the engine plant rather than at St Louis, as 72 and later it's now painted engine color. In addition, the engines were not coded for C60 vs non-C60.
So, my thought is that they could not have been using two different parts since Flint had no idea if the end car would or would not have C60.

Does that sound correct?

Patrick

Patrick------


Beginning with 1969 the part number for the waterpump hose nipple was no longer shown in the AIM. That essentially indicates that the nipple was installed at the engine plants. As I mentioned in a prior post, my 1969 was originally equipped with the "long hex" GM #3736495 nipple. However, as I recall, it was not painted but did show signs of paint on the exposed threads. This implies to me that the nipple was on the engine when the assembly was painted but some sort of temporary covering was used on the nipple.

I believe that although prior to 1969 GM had specified the 3736495 be used for non C-60 small blocks and the 3849848 be used for small blocks with C-60, either nipple could have been used with or without C-60. If so, it would not really have mattered which nipple the engine plants installed.

[Joe L.]

Re: What is correct water pump 3/4 in fitting for 1971 small block w/o AC ?

After all is said and done, attached picture is from a very low mileage 71 LT-1. Engine build date of Feb 3rd, 1971.
Gary Bosselman
[ATTACH=CONFIG]109329[/ATTACH]

Gary------

This is obviously the 3849848 nipple and it appears that it was installed on the waterpump when the engine was painted. From the photo it's hard to say if it was originally completely painted or if most of it was covered. As I mentioned above, I believe that the 3736495 on my 1969 was installed on the engine when it was painted but most of it was protected with some sort of temporary covering.