73 coolant resevoir clamps

[William M.]

Re: 73 coolant resevoir clamps

Wow. Thanks for all the responses. Some differing opinions out there.

[William M.]

Re: 73 coolant resevoir clamps

Dr Rebuild catalog says no clamp on the overflow hose, since it's not under pressure. They sell a green solid band spring clamp for the hose to the radiator. My car's got a tower clamp on that one, which I didn't think seemed right.

[Robert S.]

Re: 73 coolant resevoir clamps

Since my earlier response, I looked again at my 74' and examined the spring clamp I removed (radiator end) under magnified light and the one on the car (overflow tank end), both of which I believe to be factory original. Both are dark green, square cut edges. Also no clamp on overflow tube. Also confirmed that the replacement purchased has the newer rounded edges that I had never noticed.

[Harmon C.]

Re: 73 coolant resevoir clamps

my 4/2/73 L48 car that i have owned since new has the sharp edged spring clamps from the coolant tank cap to radiator on both ends of the hose. also the overflow hose from the tank cap to the ground has a wittek screw clamp (not the tower type)

The cars I have pictures of are NCRS Bowtie cars. The combination you have is one I belive to be original. I will check my 73's to see what I have on mine.
As I was looking close at the caps on the coolant tank I found my 75 has a much larger tube and hose than the 73's with no clamp on the hose. I have a 73 with the green spring clamps also.

[Christopher K.]

Re: 73 coolant resevoir clamps

My '73 has dark, perhaps olive green, sharp edge spring type clamps from overflow to radiator at both ends. Overflow to ground has dark side screw band clamp. This car sat for many years with the timing chain broken. Looks like these are original.
Chris

[William M.]

Re: 73 coolant resevoir clamps

my 4/2/73 L48 car that i have owned since new has the sharp edged spring clamps from the coolant tank cap to radiator on both ends of the hose. also the overflow hose from the tank cap to the ground has a wittek screw clamp (not the tower type)

Seeing that my car was built one day after yours (4/3/73) I think I'll go with your approach. Thanks to all!

[Tom R.]

Re: 73 coolant resevoir clamps

To summarize, sounds like a consensus among contributors that 73 (and 74) used the square edged, green spring clamps for the radiator to coolant recovery tank.

I took some photos at Carlisle of green spring clamps and captured a 70 LT1 clamp and a 78 Pace Car clamp, both photograhed on fuellines. Factory would have used the same clamp for the radiator to recovery tank hose.

Pictures always worth a thousand words. These contrast the square edged clamp versus round edge clamp. Note the late model clamp is green, clean and no rust...nice original clamp. We can conclude than that sometime between 75 and 78 clamps were engineered to avoid injury from the sharp edges.

Note: After doing some research in the AIMs...and some notes I've been keeping these are both GM# 3786276 and called out as such in the 1970 AIM and in the 1978 AIM...but a different configuration. I suspect they are called out in AIMs in between.

fuelline 78 web.jpg

spring clamp 70 LT1 Bowtie gasline web.jpg

[Harmon C.]

Re: 73 coolant resevoir clamps

Tom
I would say for 1973 half of the clamps I have seen are the type with the screw on the side that uses a flat blade screwdriver. The band is flat and the clamp fits just one size hose. I have pictures of the Bowtie cars but they were take before digital cameras and I don't know if I can post them. The clamps are just like the ones on the automatic transmission lines at the radiator. The 73 aim shows two 3786276 clamps and one 3786275 clamp on the overflow. I would belive one clamp is the spring type and the other on the over flow is the band type. I think Ralph Spears responded that his car has what I think the AIM calls for and I have a picture of an original owner car like Ralph's car. I think the line workers used all side screw clamps at times because of shortages or ease of installation. Joe may be able to check out the part numbers. This should put lots of doubt in a judge thinking their is only one factory correct way to judge the clamps.

[William M.]

Re: 73 coolant resevoir clamps

I found pictures of 73's in 2 reference books. 1973-1977 Corvette Fact Manual 2nd Edition by Peter J. Licastro page 66 has the solid band clamp with flat blade screw on both the hoses attached to the resevoir. Vette Vues Fact Book of the 1973-1977 Stingray by M.F. Dobbins page 21 has the same. I think Lyle is right in saying this style clamp and spring style clamp might both be correct!

[Tom R.]

Re: 73 coolant resevoir clamps

The 73 aim shows two 3786276 clamps and one 3786275 clamp on the overflow. I would believe one clamp is the spring type and the other on the over flow is the band type. I think Ralph Spears responded that his car has what I think the AIM calls for and I have a picture of an original owner car like Ralph's car. I think the line workers used all side screw clamps at times because of shortages or ease of installation.

In 78, I triangulated the numbers in the 78 AIM with what we see on original cars and concluded the following. I suspected this tracks back to 73.

3786275 is yellow
3786276 is green
9770783 is red
3829058 (black)

The AIM in 78 refers to 3829058 (black) for the coolant tank to radiator clamps...but we see both green and black spring clamps with green used at the radiator cap port. I believe workers concluded that black worked for the tank port because it was a larger diameter than the rad cap port but the smaller green worked better at the rad cap port.

Now in 73, the AIM shows a 3786276 for the fuel line clamp that shows up on 73 Corvettes as green. But your 73 rad cap port to tank port refers to the 3786275 (yellow) and 3786276 (green) both of which I suspect were too small to secure the larger diameter hose and the tank port. I suspect what they did was pick one that worked as Lyle describes.

I'm concluding in my speculation with what Lyle is suggesting...

This should put lots of doubt in a judge thinking their is only one factory correct way to judge the clamps.

But there are two issues...what to do for restoration and secondly, how to judge.

[Tom R.]

Re: 73 coolant resevoir clamps

I think Lyle is right in saying this style clamp and spring style clamp might both be correct!

I might also add that the 78 AIM sheet 13A shows a note that the green spring clamp 3786276 was superceded by 3829058 (black) I suspect to accommodate the larger port size for the coolant tank hose. So...the red did not work in 73...and they figured out in 1977 for the 78 model year.

PS...1976 AIM on page 13A shows the same note. YOur 73 AIM does not show that note

And the 73 judging guide does not reference to radiator to coolant tank hose so a judge should not be offering any deducts for clamp type and I believe that's where Lyle is coming from.

Well I've got to leave this discussion and move onto my fantasy football teams...

[Harmon C.]

Re: 73 coolant resevoir clamps

To add a little fact I found while checking out my 75 the outlet for the over flow line on the cap is much larger than the one on my 73's so the cap also changed at some point. I would say the judge who judges the radiator and the overflow tank and cap noticed that the clamps on the hose were from NAPA could and should take a deducton somewhere if it is not spelled out in any other place on the judging sheets I would include it with the overflow tank and cap. If the clamps were what we have described I said before I would take no deduction. Just because it is not completly spelled out in the manual to judge the clamps is not a reason for me not to take a deduction I know is a new part from NAPA and not original to any 73.

[Joe L.]

Re: 73 coolant resevoir clamps

To add a little fact I found while checking out my 75 the outlet for the over flow line on the cap is much larger than the one on my 73's so the cap also changed at some point. I would say the judge who judges the radiator and the overflow tank and cap noticed that the clamps on the hose were from NAPA could and should take a deducton somewhere if it is not spelled out in any other place on the judging sheets I would include it with the overflow tank and cap. If the clamps were what we have described I said before I would take no deduction. Just because it is not completly spelled out in the manual to judge the clamps is not a reason for me not to take a deduction I know is a new part from NAPA and not original to any 73.

Lyle-----

If you're talking about the coolant recovery reservoir CAP, there definitely was a difference between 1973 and 1975. 1973 used cap GM #1497193. This was a one-year-only piece. It was discontinued without supercession in May, 1975. However, cap GM #340194 will SERVICE the 1973 application.

1974 may have used cap GM #1601187 or GM #345478. GM #1601187 was the only SERVICE cap for 74-76 applications until September, 1977 when it was replaced by the GM #340194.

GM #345478 was the cap used in PRODUCTION for 1975-76. It was never available in SERVICE.

[Joe L.]

Re: 73 coolant resevoir clamps

In 78, I triangulated the numbers in the 78 AIM with what we see on original cars and concluded the following. I suspected this tracks back to 73.

3786275 is yellow
3786276 is red
9770783 is green
3829058 (black)

The AIM in 78 refers to 3829058 (black) for the coolant tank to radiator clamps...but we see both green and black spring clamps with green used at the radiator cap port. I believe workers concluded that black worked for the tank port because it was a larger diameter than the rad cap port but the smaller green worked better at the rad cap port.

Now in 73, the AIM shows a 9419381 for the fuel line clamp that shows up on 73 Corvettes as green. But your 73 rad cap port to tank port refers to the 3786275 (yellow) and 3786276 (red) both of which I suspect were too small to secure the larger diameter hose and the tank port. I suspect what they did was pick one that worked as Lyle describes.

I'm concluding in my speculation with what Lyle is suggesting...



But there are two issues...what to do for restoration and secondly, how to judge.

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.

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.

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

As far as I can tell, all of the above are flat, spring style clamps (although I have one reference which I believe is incorrect which indicates the 3786275 is a wire-style, corbin-type clamp). All are phosphate-finished but dyed the color indicated for quick identification.

As far as the "sharp" or "rounded" edges of the clamps, I strongly suspect that was a change which was effectuated at some point through a change to the specs of the original part numbers. All of the above-referenced clamps were available under the described part numbers until the early 90's. I'm sure the "sharp" edges were revised before that time.

All of the above clamps were replaced in the early 90's by METRIC-sized clamps which are close enough in size to be functionally equivalent.

[William M.]

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?