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Discussion Starter #1
I have a 351C in my 67' and a reliable source (as he restores these kinds of cars, including cougars) has told me some interesting info on my 351C. I rebuilt my Cleveland with a high volume Weiand water pump to avoid over heating which is a common occurrence in these motors. My source tells me that the high volume pump will likely blow a hole in my heater core under the hood due to high psi and I DO NOT want a coolant leak in the interior. He told me to restrict the flow to the heater by going from the factory 5/8's od size hose to a 3/8's od hole going to the inlet of the heater. Has anyone else heard this and how did they do it? Thanks for any info.
 

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Reducing the size of the hose will increase the pressure (think of when you hold your thumb over the end of a garden hose) not reduce it. That said, I still don't believe the water pump pressure would exceed the pressure of the radiator cap, or even if it did, that it would cause a leak in the heater core. Suggest you ask some of the heater core rebuilders for their opinions.
 

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Sounds like a load of poppycock to me. The pressure in the system is controlled by the radiator cap. There will not be more pressure in the system than what the cap opens up at.

Looks like Jim was typing at the same time as me, but agree with what he says. The heat ports on a Cleveland are on the water pump and the block, next to the thermostat. They are basically open to the thermostat/radiator. There is nothing to restric or increase pressure to the heater core that would be any higher or lower than that of the rest of the system.
 

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After thinking on it some more, I understand the theory behind it, but it doesn't hold water (pun intended) in real world practices.

The water pump pushes water to the heater core, the water that goes through is then returned to the block near the thermostat to be sent through the radiator. Now think of Jim's water hose explaination. It does cause pressure to increase, but it is on the back side of the restriction, which would be the water pump side. The front side would actually have less pressure, but mostly because of less water making it through the restriction.

I think that the theory behind it is that it tries to pull more water on the back side than it pushes through on the front, thus causing a negative pressure. The problem is that the water pump doesn't really create any pressure, maybe a few pounds, if that. The pressure in the heater core would still be the same if you reduced the inlet hose size, so I wouldn't bother with it. I would just make sure you have the correct radiator cap on it and be done with it.
 

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Also, the way the Cleveland is designed, it moves more water volume than any other small or medium block engine Ford makes, and most other small blocks from brands x,y, and z.
So, it's not really prone to overheating due to lack of water movement. Most of the overheating issues are caused by not using the appropriate parts, incorrect timing, and poor cooling system maintenance (burping the system, improperly flushing the block, corrosion buildup, etc). Additionally, overboring can be a problem somtimes.

Water volume is rarely a problem, if ever, when the parts and tune are correct.

I agree with those guys on the heater core issue as well ^^
 

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if your resricting the hose for flow , i'll agree on that . but , regardless of tube size---10 psi is 10 psi out--if you plug the hose beyond the restriction ,it wiil get to 10psi , but the smaller hose will take longer to reach 10psi---same as most adjustable proportioning valves---just an adjustable time delay
doctordesoto
 

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Discussion Starter #7
Thanks a lot guys. Looks like I won't mess with any restrictions on the flow to the heater core. My 351C has been punched .40 over and overheating is just something I'm worried about. I have the high volume pump, electric fan and 4 row horizontal flow aluminum radiator. I feel I did all that's possible for the coolant system so I'll just have to see what happens when I drive the car. What was said about the thumb over the end of a garden hose makes sense though...more pressure which makes me believe a larger diameter hose would make more sense. lol Thanks again!
 

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Good luck with it. I think the first gen Cougar and a 351C is a marriage made in FoMoCo heaven. like chocolate and peanut butter.
 

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Thanks a lot guys. Looks like I won't mess with any restrictions on the flow to the heater core. My 351C has been punched .40 over and overheating is just something I'm worried about. I have the high volume pump, electric fan and 4 row horizontal flow aluminum radiator. I feel I did all that's possible for the coolant system so I'll just have to see what happens when I drive the car. What was said about the thumb over the end of a garden hose makes sense though...more pressure which makes me believe a larger diameter hose would make more sense. lol Thanks again!
Well maybe my setup will make you feel a little better: .030" over, true 10:1 compression, 4 row copper radiator, standard water pump, proper 351C T-stat and restrictor and block half-filled with Hard Blok concrete. Runs nice and cool.

Regards,

Bob
 
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