I'm in the planning stages for my engine swap:

1) Got the motor picked out (350/400)
2) Found a place to get it done (I think!)
3) Confirmed that existing driveline will hold up

So my question now is, will the existing radiator be sufficient? It's new as of October.

I would think your cooling system should be OK...swapping a small block for a small block. Just remember...increasing horsepower increases heat that has to be carried away. Just make sure everything is clean and there are no restrictions. A high flow water pump may help. Make sure all the seals around the radiator are in place.

If it hasn't over headed in the past, I don't know why it would now.
I myself have never had over heating trouble, but I hear lots of people do.
Last summer I put in a ZZ-4 crate and in town or on the road it has never over heated.
Good luck with your new bullet.
Ken

As long as everything is right, it should be okay. If something was not right, it will show up. The radiator is only a small part of the total picture. There will be more heat, but you should be okay.

Redid my smallblock with some of the usual performance upgrades -- pistons, cam, pushrods, roller rockers, intake, carb, headers, exhaust. Left the radiator stock. Figured if it wasn't broken, don't fix it. Temp was decent, but pushed 200-210 in traffic. Tried a product from Red Line called "Water Wetter". It works by reducing the surface tension on the coolant mixture to the radiator fins. Dropped the temp 30 degrees. Now, even with the A/C on, temp doesn't get above 180-185. One bottle is sufficient. Cost is about $7-$8. Hope this helps.

Our C3's have one minor flaw with the cooling systems that I have a problem with and I will be making this change soon. If you have spent anytime studing race car cooling systems or stree/strip set ups you will notice that the transmission has its own cooler. Any of these conditions can be caused by a stuck thermostat, throwing a belt, a bad fan clutch or a plugged radiator.

Our C3's have the transcooler built into the radiator. There are some problems with this design.

First if the engine over heats it also over heat the transmission fluid. Secondly if the transmission over heats then it adds heat to the engine. Either way overheating can cause damage.

Secondly we all know how much heat has to funnel its way around the transmission and header make it even worse. There are reasons there are gaskets that go between the trans and the trans tunnel to keep the heat out of this area and out of the drivers compartment. We all at sometime have complained abou this heat issue.

Transmissions don't produce the heat that an engine can, but if your having trouble keeping it cool giving your trans its own cooler can help. It can also be helpful to add an oil cooler to cool the engine oil.

A word of caution you can cool an engine too much especially the oil. All oil filters have a bypass thermostat valve in them that will allow oil to pass through unfiltered until the oil warms ups then it will start filtering it. If you cool the oil too much then this valve may never close so the filter can do its job.

What would be the consequenses of a thermostat failure? Would you notice anything exept a rise in temp? Would it do anything bad?

Since it would route your coolant away from the radiator, the temperature will rise "to infinity and beyond" until you shut it down or something in the engine siezes due to oil breakdown. Maybe you'd luck out and the engine would die due to vapor lock - a rare time you'd be glad to see that! Your engine cannot maintain a workable temperature range with a thermastat stuck completely shut. Now if it were stuck part-way open, that could be a different story, but I doubt it, given the hot nature of our Vettes...

Oh sorry, I should have been more clear....I was referring to the thermostat on the oil cooler that after shark was speaking about and what would happen if it failed.

Our C3's have one minor flaw with the cooling systems that I have a problem with and I will be making this change soon. If you have spent anytime studing race car cooling systems or stree/strip set ups you will notice that the transmission has its own cooler. Any of these conditions can be caused by a stuck thermostat, throwing a belt, a bad fan clutch or a plugged radiator.

of course it inst just c3's.. just about every auto trans car ever built.

one thing to watch for when you mount a trans oil cooler..

dont mount it in front of or behind your radiator as you will just restrict radiator airflow and defeat the purpose.

you need to mount it someplace under the car where it will get air flow, but be very carefull about putting it someplace where it could get hit by a rock (lost a thm 350 this way) and just to be safe.. install a pressure gauge...

also dont use an external cooler up north... ie anyplace where you use an engine heater during the winter.

if you do.. it wont keep your trans fluid warm. (which I believe is the real function of the radiator pass through... not cooling)

if you try to drive your car with cold trans fluid it will slip like mad.. trans fluid needs to be at a higher temp to function correctly, this is just basic fluid dynamics.. pressure increases as temp increases.

I usually ran these in series with the radiator.. that way it would warm up the transmission fluid but keep it from getting too hot..