This will be a little lengthy. On the Vettes the rad. cap is about the same height or slightly lower than the thermostat. So the thermostat when the motor is cool is not sitting in the coolant. The fix is to drill a small hole so that the fluid will flow through the tstat and work properly, otherwise you get an air bubble and the tstat will not always open up right away when the motor heats up. Now I don't have an expansion tank and the LT1 cars never did the coolant just puked on the ground. This always leaves the rad down on fluid about 3 inches below the cap, therefore keeping the fluid even further away for the tstat. Now my probelm is with the FI my temp sensor mounted in the intake right by the tstat is not always in coolant and it gives the computer a false reading and keeps the fans running when the motor is not needing them. I discussed this at great length with the FI manufacter. He believes as I do that the coolant sensor is not always immeresed in fluid giving a bad reading. He suggested running a recovery tank. Not a puke tank but a recovery tank like all the newer cars are running. I agreed. Now does the tank have to be higher than the rad cap or will it suck the coolant back in to the rad. when it cools down even if it is lower. I can use my washer bottle for the recovery tank as I will put in a fitting at the bottom or I can probably use a later model C3 recovery tank form a 77 or later C3, which does mount a little higherthan my washer bottle but is this needed. Soory for the long post but I need to get this right. The car runs at the correct temp it just keeps the fan running and the computer may or may not be seeing the right temps which can cause it to run in an open loop.

 

this manifold filler cap from Morosso that I got from Summit racing keeps everything full. I use a non blowoff on the radiator and a 20 pound on the intake.

I've since plumbed in rear manifold coolant lines also

 

As long as the lines are air (water) tight the tank can be lower. Just look at the C4 Corvette for instance. The tank is low in the front bumper area.

 

The relative height of the recovery tank is unimportant, you just need to put the tube either in the bottom of the tank, or thru the cap with a tube feeding to the bottom of the tank. I like the way Gkulls setup looks, very nice and it answeres all the problems.

 

Gordonm, the '72 shop manual BB cooling system section says that the coolant level is supposed to be three inches below the neck of the overflow tank.

I haven't looked to see if it says anything different for the small block or LT-1.

These cooling systems are such a pita because everything has to go through the overflow tank.

When I had my radiator repaired I cheated and filled it through the upper hose then finished it through the tank. Much faster that way.


cc

 

gkull, I tryed one of those and my Stewart stage III pump would lift a 22 lb cap every time I blip the throtle. Had to build a flat cover for the Moroso T-stat housing on the intake to blank it off. Stewart told me not put a cap on the intake but I had to learn for myself. Coarse it may be a radiator restriction due to its inability to flow the voulume that the Stewart pump puts up. Not sure on this one.

Sorry Gordanm didn't mean to hyjack your thread, I don't think it matters if the tank is below the radiator. Make sure the hose to the radiator is off the bottom of the overflow tank.

Neal

 

Hey Gordon - wouldn't it be easier to take your temperature from the head? That would solve your problem right away. One sensor in one head for the EFI and the other for the dash gauge. My philosophy is that this allows a temperature reading closer to what's happening in the combustion chambers.

Anyway...
When you set up a recovery tank, it can be at any level in relation to the radiator - depending on your recovery tank setup as follows:
1) If the recovery tank drains into the heater lines, then the tank can be at any level higher than the heater line connection.
2) If you want the coolant drawn back into the radiator and the recovery tank has a hole in the *bottom* connecting it to the radiator cap, then the recovery tank has to be higher than the radiator cap
3) If you want coolant drawn back into the radiator and the recovery tank has a tube coming into the top of the tank, then that same tube has to go all the way to the bottom of the recovery tank. This setup allows the recovery tank to be mounted at any level - even lower than the radiator.

In setups 2 & 3, you need to make sure that the radiator cap is one of those bi-directional type like Stant. (Maybe they're all that way...)

 

Your radiator had to have some kind of cross flow problem. because my pump creates a suction and would collapse the upper hose when I blip the throttle when I tried to use a high flow Thermistat.

That is also a strange statement from Stewart. Many circle track cars use this same setup because of the low radiator position

 

Are you reversing the flow ?

 

That is a good thought. With all the later serpentine belt systems needing a water pump that turns the other direction, is it possible that maybe one got boxed wrong and you got a reverse flow pump?

 

I'm away for the weekend but this gives me a few ideas.

 

No. The lower hose has a spring in it to keep it from collapsing the upper one does not. I had to increase the flow through the T-stat to not create such a suction with a big gallon per minute racing water pump

 

the radiator is a universal aluminum, didn't think about it till now but it may be that the radiator is my restriction to flow. After talking with Jack at Stewart he told me not to run the radiator cap on the intake. I did put one there to try and remove any air that might be trapped there. I started with a 16 lb cap and worked up to a 22 lb cap but the pump would still lift it. What rediator are you running? May have to dump the one I have and try a different one.
I seem to remember you speeding up your pump with a custom pulley. Your radiator must flow a lot of water for the top hose to collapse.

thanks Neal