With all the overheating Cleveland threads we have had lately, I figured I would show one of the main reasons they do this. Mine has been running a little warm in this 95° weather, so I figured I would tear into it and find out why. I know its not my radiator or water pump, both are brand new. So I figured it had to be the notorious Cleveland bypass system. As it turns out, I was right.
Notice how the "hat" on the thermostat is smaller than the hole in the bypass restrictor? The lack of seal to the restrictor causes water to continually circulate around the bypass area in the front of the engine and doesn't let water flow to the radiator like it should.
It looks a little jagged, thats from me prying it out, but even before that the holes didn't match up. I ended up just soldering a pre 1982 penny inside the restrictor, and put a windsor thermostat in it. Hopefully this will take care of my over heating, and will help others see why this becomes an issue on the Clevelands.
If this is works i`ll do this to my engine and put it back in once the car is done or just may build a new motor and put the original one away.. Otherwise this is a great breakthru.I also emailed joe elmore on horsepower tv as i got him as a friend on facebook.I asked him in a personnal message that since you do alot of engine builds and done many small blocks and big blocks,how about doing a build on the 351 cleveland motor.Ill let you know if i get a responce and i`ll post it here.
I was actually about to post a link to that because I had forgotten to originally. I may need to do a little further explaining about how and why this works as well so people know why they are doing it.
The water pump on a Cleveland has a smaller port on the passenger side that pumps the water through the bypass circuit. When the thermostat is closed, this circuit is open and basically just circulates water around in the block until it heats up enough to open the thermostat. The design behind it is to keep the block from having hot spots before the thermostat opened up.
Once the thermostat opens, the "hat" on the Cleveland thermostat is supposed to seal against the plate and close the bypass off and allow the main water pump port to do its job. Then it should work like every other water pump setup out there. The problem is that the seal is not made most of the time.
When the seal isn't made, it allows some of the water to just circulate the block and continue to get hotter. Most will continue to go to the radiator, but it reduces the flow enough that the heat just builds up.
Now I will tell you why I don't like using the block off method, without making some modifications first. The factory design is a genius idea when working properly. Allows the water to circulate well before the thermostat opens, preventing hot spots. This is especially good for the Cleveland since the heads are known to crack at the exhaust valve seats when overheated. Blocking the bypass off doesn't allow coolant to flow through, potentially causing hot spots. But, if you drill a few 3/16" holes around the perimeter of the thermostat, you get a low amount of flow to the radiator that will prevent hot spotting. I put 6 in mine, just for the extra flow since I am working with a large amount of heat, but 2 should be plenty.
The part that Andy linked to is the easiest way by far, and I highly recommend going that route. I am just too impatient to wait 5 days (I live on the other side of the country from WCCC) for something if there is another way that will work. If you do choose the penny soldering method, there are a couple of things that are a must. You must, clean and sand any corrosion off both the brass restrictor and the penny. You must use brushable flux and solid solder. You must use a pre-1982 penny. The pennies 82 and after have zinc cores in them. If you were to just barely sand enough off the penny to expose the zinc, you would eventually have all or part of a penny skin floating around in the cooling system, or at least a car that started to overheat again. The zinc in the penny would act like a sacrificial anode that people use in radiators, and eventually it would be dissolved.
This is great info as I'm almost on the road with my 351 clevi. I installed the standard 351C thermostat but at 160 degree. I'm going to definitely look into this and contact WCCC. They have always been the antidote to the numerous cougar problems so thanks again for the pics and helpful knowledge.
The block off plate solved my problem on the Green Standard 70 and I made sure I put it on the vert. I believe the thermostat that I used is a NAPA 194.
Since posting this thread 351c owners in all makes of cars have been finding it via Google and we are selling them almost daily! Several have reported back and been very happy with the results.
That's awesome Don, glad to here it helped in more than one way.
The ebay seller that sold the repop brass plate for the longest time finally made another batch and is selling again. But at 40 bucks for his piece versus the 18 for yours, it should be easy to make a decision. Not to mention that your piece combined with a standard thermostat is more effective anyway.
I am also happy to report that mine runs much cooler since the mod. I haven't put too many miles on it since I did it, but did have it running in the driveway for over 30 minutes, idle and revving, with nothing more than 190° on the gauge. When moving down the road I haven't seen anything past 180°.
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