1969 Overflow Tank 300hp Only?
 

I came acorss a 1969 Coupe at the Pomoa Swapmeet and noticed that the car had an alumium overflow tank. When I asked the owner about it, he didn't seem to know a whole lot about the car, but said it was all stock. His looked to be an early 69 300 hp 4speed. It had the can style wiper acutuator instead of the pie pan style.

I also noticed that is radiotor was smaller than the one in my 69 350/350hp. The core support opening for the radiator was also smaller.

Sooo.... did only the alumimum expansion tank only come on the 300 hp due to the smaller radiator? I would think that the 350hp would have benifited rom the overflow so I'm confused as to why the lower horse would have it and not the higer horse.

Was this a mid production update or did they start with in from begining of production?

Hi bbp,
My understanding is that in model year 69 the aluminium radiator with aluminium expansion tank was used on the 350/300 and 350/350, 4-speed, non a/c cars. The same engines with auto trans and/or a/c used a copper radiator with no expansion tank.
Is your 350 hp car equipped with automatic transmission or a/c?
Regards,
Alan

:iagree:

Curious as to how this lore relates to 1968 small blocks as well?

-W

This subject comes up often and is subject to much misunderstanding. First off, that's not an 'overflow' tank, those didn't appear till 1973 Corvettes and are properly called 'coolant recovery' tanks. What you saw was an expansion tank, also sometimes erroneously called a 'surge' tank.

All Corvettes prior to '73 has expansion tanks. Some were external to the radiator (like this car) and some were internal to the rad itself. What governed the configuration was the type of rad that GM chose to install. If they chose a copper brass with integral filler cap and expansion tank, then there was no need or benefit in having an external expansion tank.

If they chose a stacked plate aluminum rad, this had no internal expansion tank or cap, so the external expansion tank was added.

This is why Corvettes prior to '73 must never have the rad or expansion tank filled to the top- guaranteed they will puke the excess after shutdown.

The old rule of thumb is no pre-Bubba Corvette ever had two rad caps.

Both '68 and '69 300HP or 350 HP with no air or auto had an aluminum rad with external expansion tank.

'68 and '69 with 300 or 350 HP WITH air or auto had a copper brass rad with no external expansion tank.

The NCRS judging guide has a nice matrix showing all the possible combos for the two years.

I purchased my 69 with a 350/350 no A/C 4spd in 1973. It came with a copper radiator and no external expansion tank. It was built in November 1969. Isnt this contrary to what is stated above?

:iagree: My '69 350/300 no A/C automatic also came with a copper radiator and no expansion tank.

C3 stroker's config is in accordance with the judging guide, I've revised my post above. With ref to MelWff, could be that the historical info Alan and I have is incomplete or incorrect or there are exceptions to the rule.

I've always wondered why GM used the expensive aluminum rad with external expansion tank when the brass/copper unit was more than up to the job- and cheaper to produce.

The thrust of what I was saying above is the 'no two rad cap' config. :D

That's because you have an automatic, as Mike posted, cars "WITH air or auto" used the copper radiator and no expansion tank. I can't explain the copper rad in MelWff's 69 as all 4sp no AC cars used an aluminum rad and the expansion tank. His car may have had the rad replaced by a previous owner, or it may be an automatic car converted to 4sp, there are a lot of those out there.

All 68-72 small block, no air, 4sp cars used what is commonly referred to as the 19" aluminum radiator. This rad had no filler neck, no tanks attached to it, and required the separate expansion tank. This is the same radiator that was used in all 63-67 small block cars. Chevrolet probably used it for 68-72s because they already had it on hand and knew it worked. I assume the aluminum radiator was done away with in 73, because it probably wasn't sufficient to cool the newer, hotter running, more heavily emission controlled cars.

69-72 small blocks with air AND/OR auto used a 25" copper/brass radiator with an attached tank and filler neck. 68 small blocks with AC and/or auto used the same copper/brass radiator as 66-68 big blocks, again with an integral tank and a filler neck.

69-72 no air big block cars used a 26" copper/brass radiator with attached tank and a filler neck.

The one set up I'm not sure about would be the 69-72 big block with AC. Big block AC cars used an expansion tank. The BB AC expansion tank was completely different from the aluminum ones used on small blocks. The BB one was a long thin copper one that was mounted behind the wheel well, up inside the right front fender. I'm not sure if the BB AC cars used the aluminum radiator that the 65 396s, 68-69 L-88s and 70 LT-1s used, or some other radiator, but since it had an expansion tank, I don't think it used the copper rad found in non AC big block 69-72s.

To go along with the different radiators used, there were 3 different core supports used between 69-72, one each for small block no AC 4sp cars, one for small block AC and/or auto cars and one for big blocks. 68s used different, 68 only core supports.:thumbs:

Interesting. Late production 1969 350/350hp 4speed 3.73 car. Documented. First sold 10-23-69 # 729118 . No signs of it ever having the smaller aluminum radiator or an expansion tank installed. the core support has no signs of being cut or modded to take the larger radiator.

Unless someone went to all the trouble of changing core support and radiator, i see this as an example of an exception to the rule.

Car is 95% unmodified (mainly engine has been modded, aluminum intake, headers, smog gone, acceel dual point dissy, 650 Holley dbl pump, tires, vaccum hoses, brake calipers, master cylinder, booster) other than that, the car is purely stock original.

All original panels, paint and interior. Getting shabby but, still original.

'73 also marked the introduction of the long-overdue coolant recovery tank paired with a copper brass rad similar but not identical to the previous years units. I can't imagine a setup with an aluminum rad, expansion tank and a recovery tank. No place left for the engine. :D

Not according to the AIM. LS5 option sheet B2 clearly shows an expansion tank plumbed into the heater hoses. I see no filler neck on page B6 either though it's not necessarily proof. For big block with A/C, C60 option page D5 shows a different expansion tank.

I've looked a photos of other 70 big block vettes, one an NCRS restoration, all have the aluminum expansion tank.

:iagree:
When I bought my original '69 BB non-A/C car, it had a copper/brass radiator with no filler neck and an aluminum expansion tank mounted on the passenger side inner fender. The AIM confirms this.

I am trying to figure out if my 1970 4sp w/o AC started life as a small or big block. It has the aluminum expansion tank and the aluminum radiator.

Do all big block cars have the larger brass/copper radiator even if they have an aluminum expansion tank?

The NCRS guide reflects this also. I don't think it's appropriate to assume that the configurations remained consistent from years to year. Even '68-'69 varied considerably.

From what I've seen and conversations I've had with others it appears so. I don't doubt the expansion tank is original. My question was whether it shipped with an aluminum radiator or copper/brass. People tell the copper/brass was original. Some people have been putting aluminum radiators to get better cooling. Doesn't necessarily mean its a small block radiator. The big block has a bigger radiator.

If you're wondering if yours was a conversion I'd suggest checking the AIM, LS5 option. This gives you most of the changes when when this option was ordered. The radiator is different, shown on page B5 and B6 of the LS5 option pages, AIM. If it came with A/C, option C60 shows a few more changes which apply to the big block, a different expansion tank.

Is there a number on your block, in front of the right cylinder head?
Do the casting numbers and casting dates fit the time period when your car was built?

I have a good friend who had an early 69 350/350 4 speed non AC with the copper rad & no AC and no expansion tank. I have an early also (Sept 68) 69 350/350 4 speed non AC with the aluminum rad and expansion tank. There seems to be no rhyme or reason as to what was installed - just whatever the they had in front of them that day!

Not original motor in mine, it had a 1969 CE 427 and the small aluminum radiator with aluminum expansion tank when I bought it last year. I suspect it was originally a small block car based on the radiator but the discussion about big blocks and aluminum expansion tanks made me wonder. Thanks!

:thumbs:

Is there any possibility that it might have varied due to build location? Sorry not sure if all vettes were built in one location or at various eg..... Willl Run vs Van Nuys etc...

All corvettes till mid 81 I think, were built in St. Louis. then moved to Bowling Green.