I have a 72 cutlass supreme with a freshly cleaned 4 row brass radiator, new flowkooler pump, 180* thermostat, new upper hose and custom lower hose, a dual fan setup off of an 04 Impala, with proper shroud. Engines been built 15 years ago, never a cooling problem, actually drove it from nc to Illinois, About 10 years ago I popped a head gasket, removed both heads and installed cometics multilayer gaskets, since then it seems I've not been able to drive on the interstate for awhile without putting it in neutral and coasting and allowing it to cool down, I've only got it to 210 before I repeat, th400 with 3.42 rears, Holley 750hp carb, 78 front jets, 84 rears, performer intake, 1 3/4" headers, timing is 12* initial and 36* total, 15" of steady vacuum at idle, any ideas would be much appreciated thanks

 

If you have to coast in neutral for it to cool down on the highway then perhaps the transmission is putting too much heat into the transmission cooler.

 

I do run the fluid through the radiator then through an external setrab cooler as well, I haven't thought of that

 

The trans cooler is so small in relation to the rest of the radiator that this is a non-issue.

When a car overheats at speed, the problem is usually inadequate cooling area. Normally, I'd say that your radiator is partly plugged, but if it really is a freshly-cleaned four row, that's unlikely. Were the electric fans in place before the heating problem started? They can often impede airflow at speed.

Also, since the overheating is apparently directly linked to your new head gaskets, one has to ask...

Did you check head and deck flatness before reassembly? Are you sure the new gaskets didn't have some improperly-punched holes? Have you run a leakdown test?

 

The engine did do it with a mechanical fan with the factory shroud, then I went to a clutch fan with a factory shroud, still had the problem, I did check the head and block with a known good straight edge and feeler gauges, but it's been so long ago I can't remember the numbers, I'm not sure if the head gaskets had or didn't have the correct holes, when the radiator shop cleaned the radiator they soaked it in chemicals but didn't remove the tanks, which I wasn't happy about, so I might start with a new aluminum radiator

 

When I had exactly this problem on a Chevy truck, when the truck started to overheat, you could feel that the bottom third of the radiator was still cold, because it was so plugged. Might want to try that, or an IR thermometer.

 

Okay, thanks a lot I appreciate the ideas

 

Has anyone tried the champion radiators, thinking a three row

 

I say try the Champion 2 core, has larger 1" cores. My G body Champion 3 core was well made but wasn't great at cooling my 403. In theory a large 2 core will out cool even a 4 core rad.

 

Okay so no luck on a larger Waterpump pulley, AND I have my my alternator power steer setup like the 350 olds came, so can I get a set of pulleys to fit the 350 setup?

 

Have you verified that the radiator temps are constant across the face before you go spending a lot of money and swapping parts?

 

How much variation in temp should I have from the top to the bottom, before I removed the radiator to have it rodded out (which didn't happen) because the shop chose to soak it in some chemical, I did notice with my infrared temp gun a difference but I can't remember the actual numbers

 

I'm pretty sure I have a KE Waterpump pulley and a 6.25 crank pulley the crank and Waterpump are almost 1:1 ratio that can't be good

 

This is not a very scientific answer, but when this happened on my truck, I could comfortably hold my bare hand against the bottom third of the radiator when the truck was nearly boiling over. That sounds like more than a 100 deg difference top-to-bottom. My gut says that anything over a 50 deg delta is probably too much, but that's just a guess.

 

Okay I'll try it tonight and let y'all know, did you see what I said about the crank pulley diameter Joe

 

I read through this thread, What Joe mentioned check the core for hot & cold spots would be dead accurate to the overheating issue you have. If you run hot on the highway, that means you only have partial flow through the tubes in rad which are cooled by the fan/fans. I they boiled your rad out in an acid bath agitator then I would bet some of the fins are loose in the core now. That will be a problem with overheating as well.
Also it takes a good water pump to push through 4 rows of tubes, but I see you have a new flowcooler pump.
Good luck with the outcome, Joe is keeping you on track with a good diagnosis.
Cheers
Eric

 

Just some info for those who may be reading this and have a similar problem, partially blocking the air flow across the radiator can do the same thing.

Leaf buildup, mouse nest, whatever, can block air flow and cause overheating at highway speeds. A coworker just had this issue on his truck and he discovered a clump of leaves between the radiator and the shroud, in the corner where it was difficult to see until the shroud was removed.

 

Okay so, I drove it around and got it up to 180 which is all it would go to on 45mph highway, pulled over and checked with my Mac tools infrared gun, top driverside inlet 179* bottom driverside 150*, top passenger side 175*, bottom passenger side was 160*

 

I'm running a Be Cool with twin Spal fans. If you want an easy, very reliable, but expensive fix, I just got home from running around in city traffic and then on the highway for about 20 miles in 90 degree heat with high humidity (if that makes a difference). The car runs at 180-185. ALL the time. Joe's gonna hate this post. I just know it.

No fan!

 

Also on the way back to the house through some back roads running like 25-30mph it was down to 165 so tomorrow I'm going to run the interstate to a cruise in and I'll check it again

 

I think you're THAT close to finding a way around and fixing this problem. My 2 cents. I went with my setup because I wanted complete reliability around town or wherever. I can drive this thing whenever I want. It's a good feeling to know you're not going to overheat. Cracks me up when the fans come on at a light and the guy in the next lane looks over. HIGH TECH!

 

Yeah I would like that feeling, has anyone tried the champion radiators 3 or 4 row?

 

It doesn't.

 

I do, 71 Supreme with a 496 stroker with a champion 4 row right now that runs 185-190 constant. Very hot days it can creeps towards 200 at a stoplight.

 

Awesome thanks gunmars

 

I'm in the sameish boat temps ok but on the hi way I was creeping up above 220 455 w 3:42s using AC pulleys. I bumped my jetting up in the qjet and now it's stays at 200 ish in town and went to 220 and stayed there on the highway for 10 miles at 70 mph ~3k Rpms 85* temps. When I got off the hw temps dropped right back down, I'm thinking I just can't shed the heat on the hw current rad is 3 cores from the 350 in ok condition. I plan to go w the mc161 4 core. So post back and let us know how it goes!

Mini rant friggen autoincorrect makes me re type stuff like Rpms 4 times before it doesn't change it to Rams or some other shizzle... Ok rant off

 

That's the exact radiator I'm looking at, they have a scratch and dent page, I found 2 mc161 in that section for 240-250$

 

How much air is reaching that fourth core. Just thinking.

 

I have a 2 row Be-Cool rad, very good rad for the price. IMO if you need a 4row rad to cool a stock 350-455 or even a decent street build with 9.5.1 + compression on the street. A 4 row is overkill.
If a new 3 row copper or aluminum rad won't cool the engine, then you have tuning issues IMO.
For mild stock 350-455 a 2 row is more than enough as well.

Eric

 

There's mc161 s on eBay in the 250 range

I assume air reaches every row , although I concede that air is hotter at the fourth row than it is at the first row

The 455 came from the factory w a 4 core. As Joe p has opined if the factory could get away w a cheaper rad reliably....they would.

The newer aluminum rads of today do shed heat better, but with only ~$20 difference between a 3 row and a 4 row seems to make little sense to try the 3 row.

My car has a fresh rebuilt engine w new water pump, hoses, thermostat, fan clutch stock fan and shroud w stock seals around rad. The 3 row rad cooled my 350 w np but it was in the car when I got it and is an unknown quantity unlike every other component. The car doesn't overheat but it runs up closer to hot that I want, I would rather run closer to the middle range and have a little buffer.