Freshwater upgrade for a Ford 302 V-drive.

Discussion in 'Gas Engines' started by missinginaction, Dec 27, 2018.

  1. missinginaction
    Joined: Aug 2007
    Posts: 719
    Likes: 53, Points: 28, Legacy Rep: 512
    Location: New York

    missinginaction Senior Member

    Before I start let me say that I know many will tell me something like "you should put a small block Chevy in there". I get that but the existing engine is in excellent condition. It's a 73 with about 1.200 easy hours on it. Typically slow cruising at 1800 rpm. No leaks, anything that bolts to the block has been replaced in 2014. It's raw water cooled and has always run in fresh water. The existing cooling system works fine. Based on what could be seen when the engine was out of the boat the inside of the block was remarkably clean. No sludge in the oil return galleries. I'll post a photo....

    126.JPG

    I'm going to take this boat to Florida in 2020 via the Intracoastal Waterway. Spending a long time in salt water I think it's a good idea to invest in a fresh water or closed cooling system. I'd prefer to run a "full system" rather than a "half system" and run antifreeze through the exhaust manifolds. I've been doing my homework and understand how to plumb a full system. I'll need to fabricate a block off plate for the manifold to riser joint. I'll mount a "piggy back" style cooler in the front of the engine, above and between the mufflers. Something like this.......

    98146.JPG

    If you look at my engine and the cooler you'll see that I need to install the cooler with the fittings facing the engine. For this discussion though just look at the photo and please follow along. The two studs in the center/bottom of the heat exchanger are an oil cooler mount. As I understand it the cooler will be installed as follows.

    1. 90 degree fitting on exchanger lower left is raw/sea water intake from Sherwood pump.
    2. Pipe exiting exchanger with tee fitting is raw/sea water outlet from exchanger. Hoses attach to the tee and one goes to each exhaust riser to quench the exhaust.
    2. Large fitting on bottom of exchanger feeds antifreeze to engine water pump. Antifreeze is pumped through the engine and exits the thermostat housing mounted on the intake manifold. As the antifreeze exits the thermostat housing it travels to the exhaust manifolds, travels through the manifolds and then travels to the two fittings on the expansion tank (the top tank, left and right of the pressure cap. The antifreeze then cycles through the expansion tank down through the exchanger and the process repeats itself.

    If I've got any mistakes in my plumbing please let me know. I think I'm OK with this.

    I have two major questions though.

    1. I've looked all over and cannot find a marine thermostat housing for a small block Ford that's designed for freshwater cooling. The way I see it I could use an automotive style housing. Something like this.......

    th25_1.1700.jpg

    The issue is how to get the antifreeze flowing out of the thermostat housing to the port and starboard exhaust manifolds. I think I've solved that issue by using a bronze tee fitting between the thermostat housing and the manifolds. Something like this....

    1858695.jpg
    You can attach hose barb fittings to this tee and use it as a splitter. This would solve the plumbing problem and get coolant to the manifolds.

    One last issue. How are the manifolds cooled then the thermostat is closed? Ford automotive thermostat housings have a bypass circuit that typically (in a car), runs from the thermostat housing to the water pump. I'm wondering if I could drill out the bronze tee fitting, install a nipple and get some coolant to the manifolds via the bypass circuit while the engine is warming up. It might delay the warmup a few minutes but since it's a fairly small amount of coolant, would it be a problem? I'm concerned that the manifolds could get quite hot with a closed thermostat and no coolant flow. I don't want to damage the manifolds.

    I realize that this is a long post but I wanted to cover all the bases. Please feel free to weigh in with any suggestions.

    Thanks and Happy New Year!

    MIA
     
  2. gonzo
    Joined: Aug 2002
    Posts: 13,288
    Likes: 323, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The bypass, when installed in a car, feeds the heater core. If you are running the manifolds through it, the warm up will be faster. Make sure that the heat exchanger is sized for manifold cooling. Otherwise, the heat exchanger is the same as a car radiator.
     
  3. missinginaction
    Joined: Aug 2007
    Posts: 719
    Likes: 53, Points: 28, Legacy Rep: 512
    Location: New York

    missinginaction Senior Member

    I see what you mean Gonzo. If I didn't run bypass coolant through the manifolds wouldn't there be a risk for hot spot development in the manifold water jacket? That's my biggest concern. Without that bypass connection it seems to me that there would be no coolant moving in the manifolds until the thermostat started to open. MIA
     

  4. gonzo
    Joined: Aug 2002
    Posts: 13,288
    Likes: 323, Points: 93, Legacy Rep: 2031
    Location: Milwaukee, WI

    gonzo Senior Member

    The bypass lets the coolant circulate through the engine block and manifolds before the thermostat opens. Basically it is a closed loop until it warms up, and then it opens to the heat exchanger. If you didn't use the bypass I agree the manifolds would get hot spots and cause problems.
    https://www.boatpartstore.com/images/coolfig2.jpg
    Buy Fresh Water Closed Cooling Systems for Mercruiser, OMC and Volvo Penta | PerfProTech.com https://www.perfprotech.com/buy-fresh-water-closed-cooling-systems-for-mercruiser-omc-and-volvo-penta/category/1284
     
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