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Old 09-23-2011, 06:51 PM   #1 (permalink)
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Default 351c overheating with no thermostat

My 1970 c51 cleveland has been overheating quite a bit recently so i was planning on removing/replacing the thermostat only to find out i don't have one. i notice that the heat drops consistently whenever i stop at a light or i am parked. what else could be causing this? i plan on flushing the radiator and replacing the lower rad. hose since the PO just wrapped another hose around (what i believe to be) a split hose and clamped it on. Could the lower hose be collapsing while i am driving? What else should i check for?

PS: My oil pressure has been relatively high (pretty much as far as the needle can move) ever since i drove it on the highway a couple weeks back
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Old 09-23-2011, 07:39 PM   #2 (permalink)
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You're probably overheating because you don't have a thermostat.
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Old 09-23-2011, 07:49 PM   #3 (permalink)
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Quote:
Originally Posted by Maxum96 View Post
You're probably overheating because you don't have a thermostat.
Could you elaborate?^
On my cj5 i took out the thermostat and it ran chill as a cucumber.
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Old 09-23-2011, 08:01 PM   #4 (permalink)
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351C has an internal bypass. The 351C thermostat is special and without it, some water will go through the bypass and keep circulating in the motor without going through the radiator. Also, removing the thermostat on any motor can allow the water to pass through the radiator too fast and not allow the radiator to absorb enough heat from the water to cool it before it returns to the motor. That's why racing engines will often using restrictors (look like giant washers) to restrict the water flow instead of using a thermostat.

351C thermostat

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Old 09-23-2011, 08:06 PM   #5 (permalink)
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Cool when slow/idling but hot when zipping along tends to mean some kind of flow restriction, which could be as simple as that lower hose (and many here swear by having a spring in it to prevent this very thing), or as tough as plugged passages in the block. A slipping belt could be an issue as well (when the pump is needing more power at higher rpm). A bit of a long shot, but easy to check.

Of course, the the ancient gauges can't always be relied upon, either.

I'm not sure how not having a 'stat could lead to overheating (other problems, but not overheating...)

Good luck!
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Old 09-23-2011, 08:21 PM   #6 (permalink)
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First flush the system well and ad a RobertShaw 333-180 stat with the restrictor plate installed for a C engine.

Flow restriction inside the block happens in a C engine at speed without a stat installed.
Without it the 70% of coolant is passing thru the rad without first going thru the block to exchange heat.

If your going to run a C engine without a stat/res plate installed,
You MUST plug off the bypass hole in the block.
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Old 09-23-2011, 09:00 PM   #7 (permalink)
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thanks for the help. I'll be buying that thermostat this weekend. I was looking the thermostat up online at oreilly's and it was listed as race-only. Can someone give me some insight on this too?
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Old 09-24-2011, 07:36 AM   #8 (permalink)
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As has been mentioned make sure the restrictor plate is there under the tstat and make sure you get the correct cleveland tstat. Another option is to purchase a restrictor block off which allows the use of a more common windsor tstat. I haven't tried this myself but others have reported good results. More info here:

http://www.mercurycougar.net/forums/...ght=clevelands
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Old 09-24-2011, 09:36 AM   #9 (permalink)
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Default Thermostats for Clevelands----Not your typical Ford

proper 351c thermostat - Clevelands Forever!

Stant
180 29468 Cleveland specific
Stant 192 29469 Cleveland specific Stant 180 13468 Cleveland specific Stant 192 13469 Cleveland specific Stant 192 S-346-192
Gates 180 33128 Cleveland specific Gates 192 33129 Cleveland specific RobertShaw 180 333-180 Cleveland specific Ford/Motorcraft 180 RT-310 Cleveland specific Ford/Motorcraft 192 RT-139 Cleveland specific; 70-73 351C,351CJ, & Boss 351 Ford 180 D7PZ-8575-A Cleveland specific Napa 180 197 Cleveland specific
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Old 09-24-2011, 10:45 AM   #10 (permalink)
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Dollars to doughnuts the PO removed the thermostat because it was overheating and he erroneiously thought this would help. You definitely need a thermostat in a 351 Cleveland; as mentioned, it's not like other Ford blocks. I would recommend going to NAPA to get it. Otherwise, the parts guy will try to sell you a Windsor thermostat and tell you all Ford V8 thermostats are the same.

Thus, since you'll be working on the cooling system anyway, it would be a good idea to pull the radiator and take it to a good shop. They will run a flow test on it and fix anything that needs fixing. Old Mustang radiators are notorious for getting clogged. And you cannot unclog it yourself.

Then, install the freshly cleaned radiator, new hoses, and the new thermostat. While you're at it, you might consider also replacing the water pump. Then you'll be golden!
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