1971 Corvette 350 Automatic

Looking at DeWitts website I'm noticing that my vette currently has a radiator similar to the 1973 version. I'm not going that route because it doesn't fit well, but curious if I should go BB or SB. Cooling and Fit is my concern, originality is not. I would assume the BB is better cooling or is it just different in design? And as I have never seen a radiator without a radiator cap, how the heck do you fill the BB rad?

1973: http://www.dewitts.com/pages/product...asp?ProdID=281
1969-72 BB: http://www.dewitts.com/pages/product...asp?ProdID=283
1969-72 SB: http://www.dewitts.com/pages/product...asp?ProdID=280

 

Only the base small block cars had radiators with caps in the early 70's. The other engines had an 'overflow' tank mounted under the right-side front fender. The pressure cap was fixed to the overflow tank, rather than the radiator. With that design, you fill the radiator completely [via the o'flow tank], then continue filling to the COLD line on the o'flow tank with the cap OFF. Fire the car up and let it warm up so the T-stat opens, then keep tank up to the COLD line as air escapes from the system. Once all the air is out and the engine up to temp, the tank it then filled to the HOT line and the pressure cap put back on.

In operation, as the engine heats up and coolant expands, the excess fills the o'flow tank; as the engine cools back down and the fluid contracts, the radiator stays full by drawing fluid from the tank. So, the radiator stays full all the time and fluid level changes only in the tank.

If you do not have an o'flow tank, then you have to leave expansion air space in the radiator before you put the cap back on.

 

Great info here 7T1. If I understand this, the difference is the BB adds additional fluid in the reservoir, but the tanks and cores would be identical. Thus, BB cooling would cool better due to having more fluid, but it would likely be minimal.

 

I always wondered why water would leak out when I opened mine, well it only took 15 years to figure it out could have been worse

 

It's called an expansion tank. Later C3's had overflow tanks and with that switch the radiator cap went back onto the radiator.

Expansion tank:

Part of pressurized cooling system. The expansion tank has the radiator cap. The tank has air in it to compensate for the hot coolant expanding.

Advantage: More pressurized coolant available to cool engine.
Disadvantage: Air will be in the system and can promote corrosion.

Overflow tank:

Non-pressurized. Pressurized system has no air in. Hot coolant will expand by opening radiator cap pressure valve and go into overflow tank. When engine cools the system sucks coolant back from the overflow tank.

Advantage: No air in pressurized system.
Disadvantage: Less overall capacity.

 

Hi,
Just to clarify here...
The base engine with 4-speed had an aluminiun radiator with an aluminium expansion tank (with a 15# radiator cap) in 70-72.
The base engine with auto trans and/or A/C had the copper radiator with the 15# radiator cap and no expansion tank in 70-72.
I believe the BB radiators cooled more because of their bigger cores, not because of their aluminium or brass overflow tanks.
Regards,
Alan

 

Thanks for the clarification on the tanks.

 

[QUOTE=71_S-Ray;1573756980]1971 Corvette 350 Automatic

Looking at DeWitts website I'm noticing that my vette currently has a radiator similar to the 1973 version. I'm not going that route because it doesn't fit well, but curious if I should go BB or SB. Cooling and Fit is my concern, originality is not. I would assume the BB is better cooling or is it just different in design? And as I have never seen a radiator without a radiator cap, how the heck do you fill the BB rad?

1973: http://www.dewitts.com/pages/product...asp?ProdID=281
1969-72 BB: http://www.dewitts.com/pages/product...asp?ProdID=283
1969-72 SB: http://www.dewitts.com/pages/product...asp?ProdID=280[/QUOTE

If you currently have the 73 style radiator in there it's no surpirse it doesn't fit well. That core (and the BB) uses a 27.5" core section, while the correct SB one (last link) has a 26" core section.

All these radaitors are huge in comparision to any others Corvette generation and there is really no reason to alter something or make changes to get one in there over the other. I'd just go with what fit's your currently core support. If you still have the 26" support, then used the A70 sb without a expansion tank.

Measuring radiators and core supports has always been a subject of confusion. When measuring a radiator, you only want to measure the fin area only. This is the distance between the two headers.
When measuring core supports you want to measure the center line of the U brackets. The easiest way to do this is too hook your tape measure on the outside edge of one bracket and measure to the inside edge of the other. That will give you the center line which is exactly 1/2" larger than the core dimension.

So, the 26" radiator core will have 26 1/2" U brackets on center.
and the 27.5" radiator core will have 28" on center.

Hope that helps

 

Thanks for all the replies. They really cleared this up for me. I'll definitely be going back to the stock rad that fits my car, but unfortunately I have to deal with a stuck valve first. The constant fixing never changes. It's the priority of what's next that changes.