73 coolant resevoir clamps

[William M.]

Re: 73 coolant resevoir clamps

Mine has the solid band clamp with flat blade screw on the hose going to the radiator and no clamp on the overflow hose (yes, I know I have the wrong fan and I'm missing my smog)

[Joe L.]

Re: 73 coolant resevoir clamps

Here's what looking at engine compartment pictures of 73's on sale on e-bay has turned up: the majority have the solid band clamp with flat blade screw. While most of these cars aren't exactly Top Flight examples, this style clamp is definitely the most common. Am I just seeing car after car where owners replaced the original spring clamps? Or were these what the cars left St. Louis with?

William-----


I don't think they've been replaced. For one thing, the band-style clamp with side screw of the configuration pictured is generally a PRODUCTION-style clamp. I consider it unlikely that such a clamp would have been used in a field replacement situation. For field replacement, it's FAR, FAR more likely that a stainless steel, worm screw type clamp would have been used. So, I have no real doubt that clamps such as the ones seen on your car are original.

However, these clamps are are certainly not the ones that GM specified to be used as shown in the AIM and as also seen on other apparently known-original cars. Generally, I have noted the band-style, spring clamps for the coolant reservoir hose, but I do not doubt that others were used. Here's what I think happened:

The band-style spring clamps have a very narrow range of hose OD size that they are designed to effectively work with. For instance, I believe that the reason for the change from the 3786276 to the 3829058 probably occurred because there was a slight change in the OD of the hose at some point. Keep in mind that the sort of hose that was used for the coolant reservoir was a commodity-type item---it was supplied by different suppliers and there may have been slight or,perhaps, not-so-slight differences in the OD of the tubing used by the assembly plants. When tubing OD changed, there was likely a need to change clamps since, as I mentioned, the band-style spring clamps work within a very narrow range of hose OD size.

The 3786276 and 3829058 would work for 2 slightly different hose OD sizes. However, what if another slightly different yet hose OD size began to be supplied? GM may not have had another spring-style clamp available which would work with that size hose. However, the band style, side screw clamp would have a wider range of hose sizes that it would work with. So, perhaps it was decided, at some point, to just go ahead and use this style clamp which would work with whatever slightly different OD size hoses were supplied. Or, it may be that the band style, screw clamp was used only when the factory was receiving and installing the "oddball" size hose OD. The one thing that surprises me, though, is the fact that the side screw clamps were apparently used with the cap end of the reservoir hose. That's because the nipple on this end is PLASTIC. The side screw clamps can cause breakage of the plastic and I don't know of another application in which a side screw style clamp was used with a plastic nipple.

I believe the band style , side screw clamps used were GM #9420534. This was a PRODUCTION-only clamp, not available from GM in SERVICE and not typically available in the aftermarket.

[Tom R.]

Re: 73 coolant resevoir clamps

[quote=Joe Lucia (12484);367244]Tom-----

I think you have the 3786276 and the 9770783 reversed. The 3786276 is GREEN. The 9770783 is RED. The 3786275 is YELLOW and the 3829058 is BLACK, as you have noted. ]/quote]

Thanks Joe...yeah, caught that later in the afternoon and corrected the comments above to avoid confusion among future readers.

I'm not sure about the 3786275. However, it's designed to work with rubber tubing of 9/16" OD size.

We see increased use of the 3786275 clamp in later C3 years to secure the headlight actuator hoses, cruise control and, occassionally a carb port.

[Tom R.]

Re: 73 coolant resevoir clamps

As far as I can tell, the 9770783 is designed for use with rubber hose for 1/4" tube size. The 3786276 and 3829058 are designed for use with 3/8" tube size, but are slightly different to accommodate different OD rubber hose used with 3/8" tube.

Joe...how about Silver 14007703? What size hose was it intended to secure? This was late C3 to secure the emission hose from canister to the lower left front carb port.

[Joe L.]

Re: 73 coolant resevoir clamps

Joe...how about Silver 14007703? What size hose was it intended to secure? This was late C3 to secure the emission hose from canister to the lower left front carb port.

Tom----


I have not been able to come up with much information on the 14007703. It was a PRODUCTION-only piece and was never available in SERVICE. Applications originally using it were SERVICED by GM #2494772 and, later, GM #25518880 and GM #1648216. However, the 14007703 was a band style, spring clamp. The SERVICE clamps were all worm screw type clamps with a size range of 1/4" to 5/8". The 14007703, being a spring clamp, had a much narrower range but all I could say about it is that it was designed for use with a hose OD of somewhere between 1/4" and 5/8".