What's the deal with radiator cap rating and coolant systems?

[71CHEVYSHORTBED402]

Originally Posted by davischevy

I had an extra NOS tank on the shelf with no mounting bracket. The other day a guy gave us a bunch of stuff off a really nice 70 CST truck.

My son in law put the stash in storage. I was checking the goods over last week and there on the shelf was a complete overflow setup, yellow tank and bracket. Now I have a bracket for that NOS tank.

My red and white 72 has never had an overflow tank, and I have had no problems.

Odds of that aren't that high. OT I'm not found of the instructions how to mount said bracket. They tell you to mount it off-kilter, probably because the nozzle doesn't clear the voltage reg. connect. It's so close the radiator as well, and seemed to high or low, I don't remember. I lost the regulator so no shortage of real estate. Made a bracket for the bracket, rivet screws with kep-nuts instead of the taps that came with the kits.

I had the impression a tank was the better option. After reading this thread it appears it doesn't have to be.

[davischevy]

Originally Posted by 71CHEVYSHORTBED402

Odds of that aren't that high. OT I'm not found of the instructions how to mount said bracket. They tell you to mount it off-kilter, probably because the nozzle doesn't clear the voltage reg. connect. It's so close the radiator as well, and seemed to high or low, I don't remember. I lost the regulator so no shortage of real estate. Made a bracket for the bracket, rivet screws with kep-nuts instead of the taps that came with the kits.

I had the impression a tank was the better option. After reading this thread it appears it doesn't have to be.

I had an NOS Vega setup on the shelf so after thirty two years I put it on my red and white truck a couple of months ago.

I put one on my Longhorn because it's a big block. As it turns out, it's the coolest running big block I have ever had.

What ever cap you use with the tank, it needs the arrows on it. One arrow will point to the overflow tube.

I called that tank NOS. That was not intended to insinuate the tanks were available from the factory on our trucks.

[71CHEVYSHORTBED402]

Originally Posted by davischevy

I had an NOS Vega setup on the shelf so after thirty two years I put it on my red and white truck a couple of months ago.

I put one on my Longhorn because it's a big block. As it turns out, it's the coolest running big block I have ever had.

What ever cap you use with the tank, it needs the arrows on it. One arrow will point to the overflow tube.

I called that tank NOS. That was not intended to insinuate the tanks were available from the factory on our trucks.

"What ever cap you use with the tank, it needs the arrows on it. One arrow will point to the overflow tube."....Say what?

Believe or not the expansion tanks were available from factory on rare occasion. Shows on the SPID and I believe those were Govt. trucks. The only question I have is did they use the blue cap per kit instructions or leave the better cap in place

[DeadheadNM]

I'll trade an RC15 for your blue cap.

[davischevy]

I may have missed it, but what kind of cap did the trucks with factory installed overflow have?

[71CHEVYSHORTBED402]

Originally Posted by davischevy

I may have missed it, but what kind of cap did the trucks with factory installed overflow have?

That's what I want to know Either RC15 like without the tank or they swapped it out for the blue one in the kit.

Originally Posted by DeadheadNM

I'll trade an RC15 for your blue cap.

Not sure what I'm doing with it. If I were to be tempted by an RC15 then it depends on the RC15

[davischevy]

I have never seen a coolant overflow on a SPID on a 67-72.

[davischevy]

[QUOTE=davischevy;8738865]

What ever cap you use with the tank, it needs the arrows on it. One arrow will point to the overflow tube.

/QUOTE]

I guess nothing is absolute. I should have said "unless closed system is noted on the cap".

[Ol Blue K20]

It definitely needs to be a recovery type cap. A closed system cap will push it in the tank but will be unable to draw back to the radiator.

[71CHEVYSHORTBED402]

Originally Posted by davischevy

I have never seen a coolant overflow on a SPID on a 67-72.

You got me there. I can't seem to locate the thread on the topic. If I remember right it was concluded best guess some govt. trucks were stocked with the coolant tanks & SPIDs to match.

Here's one, post 5. I don't know enough to tell what year this SPID is, and I can't read the RPO code. I'm surprised nobody commented on it: Post 5 http://67-72chevytrucks.com/vboard/s...d.php?t=546610

[71CHEVYSHORTBED402]

BOOM! This isn't the SPID I recall but good enough. 72 Chevy, RPO 8B6, which matches the SPID I linked to earlier.

Post 21: http://67-72chevytrucks.com/vboard/s...d.php?t=560500


Rare enough the RPO isn't included here: http://outintheshop.com/options.html