Just traded for a '71 454 Corvette and had a question for you Corvette experts. Do these big block cars have a problem with overheating? Mine keeps on puking out coolant when I drive it. But the temp gauge only shows around 160. I had a Viper RT/10 that ran sometimes up to 250 and it never puked out coolant like this thing does. I thought it might have been the radiator cap so I bought a new 16lb cap but no change. Would a bad thermostat act this way. It has a new 4 row after market aluminum radiator. It hasn't even started getting hot yet so I need to remedy this before it does. Any info would be appreciated.

 

My experience with a stroked Road Runner & my own 71 -454 is that I always thought that the water level should be at the bottom of the inlet when cold. After talking with several knowledgeable people I learned that the radiator will find its own level by releasing some of the fluid once it warms up. ( cold/hot levels are different ) I used a laser temp gun to confirm that the actual temp matched that on the gauge.
Hope this helps.

 

Originally Posted by saunderscx View Post
I have an aftermarket aluminum radiator in a 72 C3 roadster with a 350SB. The original GM "expansion tank" is long gone.
I've looked at the "OE expansion tank" diagram briefly last week. The tank is like $170, then there's a cap, bracket, two straps, and T to tie into heater hoses. I more or less stopped looking at the diagram because that's not what I'm after. It seems the OE expansion tank is designed to work under pressure, but I think that's not at all a necessary thing with a modern aluminum radiator. Right ??
What are your thoughts on this ?
I see a lot of mistakes regarding this "missing tank". That is because many people see a car the same year as theirs and it has the tank, therefore your tank must be missing, right?
No. Only base C3 small block (no AC, no Auto, and no special engine) and BB cars have the factory aluminum surge tank. If your sb car has anyone of these options, then you would not have the pressurized surge tank. The filler neck with cap was on the radiator and there is no need for one.
If you really want to use a catch can, you could just order a plastic one from a 73 or later. I don't see why you would need it but it would work. Normally you would fill the radiator about 3" low and this room allows for fluid expansion when it heats up. If you overfill the radiator it will push this extra fluid out when it expands. Often people will confuse this with boiling out or puking. Then they re-fill the system when it cools down because they feel they need to and this madness continues over and over.
Last edited by Tom DeWitt; 11-03-2016 at 01:35 AM.
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Hi rs,
The big block engines generate a lot of heat.
It's important that ALL the proper parts of the cooling system are in place and working the way they were designed to.
This includes the water pump, fan, fan clutch, thermostat.
The radiator, cap, and the shroud.
The many seals from the shroud to the radiator and core support, the seals from the core support to the hood, and the seal from the lower valance to the core support. The idea is that it's the seals that insure that the fan is actually able to pull the air through the radiator and not around it.
It takes all these parts to properly cool the engine.
Regards,
Alan

All these parts are identified in the Assembly Manual.
Do you know about the Assembly Manual ... or perhaps you have one?

 

with Alan

Also be aware that when you pull in to park, the internal temps of the engine are still high. I would suggest that you do the following and see if it helps.

1- go to 60 - 65% antifreeze as it will raise the boiling point of the mix
2 - when you pull in let the engine idle for a minute or two
3- drill a 1/16 - 1/8 hole in the thermostat (flat area). It allows the fluid to be circulating before the stat opens.

Check the engine temperature of the engine at the water neck, and at the intake manifold where the intake manifold meets the heads - water passage on both sides. They should be close in temp.

The water level will not be at the top of the radiator filler. It will find a level 1" down or so.

The overflow tanks allowed the radiator to always be completely filled by absorbing the overflow and returning it as the engine ran hot or cold. Thus the radiators were able to be slightly smaller and still work.

A worn clutch fan can and does cause troubles - it will not allow the fan to bull enough air, as does the incorrect fan.

I did a friends 327 -67 with a/c. they changed everything - I found it had the incorrect fan, the A/C fan has more twist in the blades - thus pulling more air...

 

my 427 with all new parts will spit out anti freeze when i have a brain fart and add a little too much to the expansion tank.

 

Then you are not overheating. You are over filling, just let it push the extra fluid out and stop adding more.

 

well I had the same problem with a small block ,and all it was just the radiator cap!

 

I sure do appreciate the help here. I have a '71 SB with the "spitting out" issue. Just got it back from a shop (five months) and they did a tran rebuild, rear end rebuild, and lots more, but it never had this issue with them, and after all the money, I thought I'd tackle it again. I'm going to review the cap psi first, then the thermostat, and finally the fan clutch. It's always done this, and I replaced that stuff years ago. Maybe I got the wrong parts, dunno. I'll keep checking in. Thanks all!

 

Some auto parts stores will loan you a cooling system pressure tester. You can pressurize the cold cooling system to the pressure labeled on the radiator cap. Allow it to sit for 15-30 minutes......then read the gauge to make sure it has not dropped in pressure. Also look over the hoses heads radiator block & heater core for leaks. Check your engine timing. Check for leaking head gaskets.

I could have saved myself lots of time by doing the pressure test first.

 

this also will help find leaks, if any are present. IMO

 

Thank you! Well, the shop was supposed to have tested for that as I'd mentioned the problem. But I was paying big time for frame welding, rear end gear rebuild, tranny rebuild and more. Figured I'd go in search of my heating issue. I'm going to start with the cap and whittle it down. Much thanks again!!!