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Discussion Starter #1
Today in Sunny Pasadena I took my day old fresh restoration for a ride to see how she'd handle 93 degree atmosphere. he 351 is pushing the radiator to the limits. It's a stock replacement that came with the car, so it's almost new. On cooler days, she does OK, but it's over 90 almost every day in the valley during the summer. Today I'm pushing 210 with a 180 stat. Any suggestions for a bigger (deeper core) radiator? Summit sells what appears to be a stock unit.
 

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Discussion Starter #5
I've got a big blade 17" fan about 1 1/2" from the radiator, so it pulls a whole lot of air through. I don't think a shroud would help in this case. Shrouds make the biggest difference when the fan is far from the rad. No A/C in this car. I really want to keep the stock look on this car so a aluminum radiator is probably not my first choice. Even though I can paint them, they look completely aftermarket.
 

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I agree on the looks of aluminum. Shrouds might do more than you think, the fan can suck air in from the sides without going through the radiator. I used to put in dealer AC and most kits would come with a fan and a shroud, rubber side seals for the radiator. Some cars would even have a flap to seal the hood so no warm air can get back in front. Are you using the big block style radiator with the rubber clamp type mount or small block with the side mounts?
 

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I would set aside all assumptions, and test for what's actually lacking. My first two tests:

  1. Fully warm, take it up to sustained mid-cruise speeds, and high-cruise (highway). If the engine cools-off, the rad is fine, and it's an airflow issue. Shroud it.
  2. Still hot? Install a cooler performance (160° to 175°) thermostat. Does it still hit 220°? If so, it's a radiator issue. If not, it's a circulation issue.
Armed with that info, hopefully you can address the problem more directly.

David
 

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Discussion Starter #8
Sure, I'll try a couple of more tests. I don't want to spend money I don't need to.
I noticed it hitting 210 at idle after a few mile drive. Outside temp was 93 degrees. If a thermostat's job is to keep the coolant in the radiator long enough to cool down before letting it back in, I can't see how a cooler stat will change things in this case. With hot outside air a radiator with more surface area or better conductive capability would hopefully be able to transfer the heat before hitting the block again. A cooler stat would let the coolant out of the block sooner, but if the heat can't be exchanged fast enough I'm still gonna run hot.
 

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If a thermostat's job is to keep the coolant in the radiator long enough to cool down before letting it back in, I can't see how a cooler stat will change things in this case.
No, a thermostat's job is to begin opening at the rated temp, then only open more if the temp continues to rise. It shoud regulate temperature between 5° and 15° above rated temp (20° under extreme loads). If it cannot, then the cooling system is not capable of cooling well enough. If it can, the cooling system is fine, and capable of staying 5-15° above rated temp. If it cannot maintain temp, it doesn't matter what the thermostat is or how open it is, as the cooling system is not capable of shedding enough heat. See what I mean? It's a cooling capacity test.
With hot outside air a radiator with more surface area or better conductive capability would hopefully be able to transfer the heat before hitting the block again. A cooler stat would let the coolant out of the block sooner, but if the heat can't be exchanged fast enough I'm still gonna run hot.
Exactly. So, if it still runs hot with a cooler T-stat, then you have a crippled system. Another indicator is the temp difference between the radiator inlet and outlet. A functioning radiator will be 10-20° cooler at the outlet at max temp. Any smaller spread means the radiator or airflow is insufficient to carry the heat away.

If the spread is good, then you're looking at a lack of circulation, or for something that is adding more heat than it should, such as ignition advance issues. Just for comparison, I have a puny stock original 17" 2-row 302/351 radiator in-front of my 351W/427 stroker with a Ford 7-blade clutch fan and shroud. It stays cool in summer idling or driving. While big radiators are nice and can't hurt, it may not be the actual problem(s).

David
 

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Discussion Starter #10 (Edited)
Yea, I had it stat backwards. Well, It's cool here today, (68) so I'll take her out for a run and see what temps I get. When I drove and raced all these cars back in the 80's I never ran too hot even in the hottest NY summers. The cars are now classics and have all kinds of issues keeping them happy. Freaking Prima Donas! :) Here's a link to my restoration site to see the princess in question- http://www.mechanknuckle.com
 

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Discussion Starter #11
Test results fully warmed up with outside temp at 70.

Cruising and at stop lights- 180
Afterwards, stopped and idling for five minutes- 190-195
Stopped, revving at around 2200- temp comes back down to around 185 and probably lower if given some time.

What do you think?
 

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Test results fully warmed up with outside temp at 70.

Cruising and at stop lights- 180
Afterwards, stopped and idling for five minutes- 190-195
Stopped, revving at around 2200- temp comes back down to around 185 and probably lower if given some time.

What do you think?
Assuming you have proper idle ignition advance ;), the fact it can stay cool with airflow at speed, but not idling, would indicate an airflow issue. It cools just fine even with higher load and RPM on the highway (ram airflow), and when the fan is spinning-up at 2200 in Park. To reassure yourself you're on the right track, start the engine COLD with the radiator cap off. When it hits 180°, you should see coolant flow in the radiator, increasing with temp. This also confirms it's an airflow issue, and not an oddball coolant-flow restriction on a fresh engine.

David
 
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