I have a 75 CJ5 with a Chevy 327, it always runs hot. It has never overheated as of yet, but it always run about 210 degrees. I've tried lifting the engine with mounts from Advance Adapters to get the engine centered with the radiator. I've replaced the fan shroud that was missing, flushed cooling system, eveything. Why's it still running so hot?  

What radiator do you have? What degree thermostat?  

How do you know it is 210? Have you used a mechanical temp gauge on it? Shroud and fan are more important than anything else when doing a engine conversion.

What kind of fan and is it shrouded correctly. That is the fan should be at least 1" in the shroud, but not more than half the width of the fan, and no more than 1" to 2" clearance from the blade tips to the shroud for clearance.

210 is not hot. If it runs 210 all the time, that is great. When an engine runs 40 degree differentials, all that heat'n and cool'n takes a toll on the motor as far as expanding and contracting.  

210 isn't really to hot for a fuel injected/computer controled engine,... Its ok for a carbed 327. they never had much more presure than 7psi on the open  radiator cooling system.

todays 18psi systems raise the boiling point to make 220 no big deal

the 327 should have a 180 t-stat unless its injected.  

Just a thought, but have you checked your ignition timing and fuel curve? Or possibly even running too hot of a spark plug. Too much timing advance will cause overheating; a lean fuel condition will cause overheating; and a step or so hot on the spark plugs will also cause overheating.  

The t-stat is 180 and the cap is a 12 psi cap. Shroud installed properly, if 210 is Ok then I'm good. Unless any one else thinks it's to hot. I was thinking it was because a buddy of mine has 454 in his CJ7 and it only runs about 190 degrees. I do get some fluxtuation in temp, 190 running on highway it jumps to 210 sitting in traffic and on the trail. Thats why all the fuss, I feel thats to much of a differance.  

I think the radiator is one of the most important items when swaping motors. You dont wana take a 4 cyl jeep swap in a v8 and leave the 4 cyl. radiator. That would be silly! Ther radiator does make a difference! Are you running a single row brass radiator or a triple row aluminum radiator? Theres a big difference in the cooling factor there!  

A radiator is a heat exchanger. The efficientcy of the heat exchange has more to do with the radiator build materials and air movement through the radiator than the size of the radiator.

There is a disadvantage to thicker multi row radiators. Multi row radiators cause more static pressure build up, which actually makes them less efficient because less air volume can run through them.

Frontal area is also more important than thickness, but is usually dictated by grill size. And in a CJ, there's not much.

If a vehicle keeps it's cool above 35 mph, then the radiator is properly sized. If the vehicle heats when sitting in traffic, then there is an air flow problem. If you install a bigger radiator and don't address the air flow, one thing will happen. It will just take a little longer to heat up to the same temp as the smaller radiator.

Change a copper and brass radiator to aluminum? Ya, that will help. More rows? Won't help a thing. You have to increase air flow through the radiator. Just like going down the road increases air flow.

Bigger dia fan, steeper blade pitch, new clutch, aux fan, hood vents and reduced skid plating to reduce static pressure under the hood, and a propperly designed shroud, are all going to be the way you fix in-traffic heating issues. Not a multi-row radiator.  

Other things that don't help, higher flow water pumps and electric water pumps.

Another thing that can help, reduce or eliminate the anti-freeze. Water is more efficient at exchanging heat than anti-freeze. Never run more than a 50/50 mixture. Use only enough ant-freeze ratio to protect against the low temps in your area. In the summer use a RedLine product for anti-corrosion, and forgo the anti-freeze altogether. This can help 5-10 degrees.

What happens to the temp if you lift the hood and let it sit there and idle for 30 minutes?  

It's an older engine. They are best run at 180-195 or so. 210 ain't bad but I wouldn't want mine to run that hot and it doesn't give you much room for error if something goes wrong. But you just solved your own problem. On the highway the radiator is getting plenty of air so the engine runs cool. In traffic and on the trail it is not. You clearly have an airflow problem. Either the fan is not moving enough, the radiator fins are plugged, or your shroud is not tight enough around the fan. If you can fit one I highly recommend one of the rigid steel race fans from Flex-a-lite http://www.flex-a-lite.com/auto/html/race-fans.html

And, contrary to what others say Flow Kooler pumps do make a big difference over cheap part-store pumps. But water flow does not seem to be your issue.  

Moving coolant through the radiator too fast can be counter productive, as can too slowly. The thermostat controls flow.

The guys that designed the water pump and the speed that the pump runs via the pulley size, are pretty sharp. They have probably even done some testing to arrive at their conclusions.

So, generally I would not say messing with flow rates, without some specific knowledge, coupled with testing, would be good advice.

That's what I'm trying to say about after-market hi-flow pumps. I think they do make a difference, and it might not be the difference you want.  

It has to do with the size and number of rows! So i guess the 427 overheating in my nova had nothing to do with the brass radiator which was a 2 row with half inch rows? but when i put an aluminum 2 row with 1 inch rows in i can sit with it idling for a half hour and it dont go over 180?  

The fan cools the water/antifreeze in the radiator. The more water/antifreeze in the radiator, the more that is gona get cooled. The more water/antifreeze that comes in contact with the rows, the better. The heat is exchanged through the rows and fins. The more surfaces of the radiator for the coolant to touch, would be best.  

So, it's all about heat being transfered from the water/antifreeze to the rows and fins. Then what?

Are you forgetting about the heat transfer from the rows and fins to the air. And if the heat is now in the air and you move the hot air and replace it with cooler air...

Wow, you can see pretty quick how moving more air can disipate more heat.

This is basic thermodynamics for a high efficiency air to water heat exchanger.

There's lots written on the subject, you don't even need to make it up using anecdotal evidence.  

ok, so it looks like we both have good points. you need to move a lot of air and you prolly dont wana be using your 33 year old radiator, if thats what it has.