Water Pump Pulley

Discussion in ''Da Nailhead' started by Nick32vic, Jun 20, 2007.

  1. Nick32vic

    Nick32vic Well-Known Member

    HI, My 425 overheats when i go fast. I have a list of things im gonna try to fix it. One of them is get a smaller water pump pulley. Are they interchangeable with other waterpump pulleys? If not were can I get a small one for my 425?
     
  2. nailheadina67

    nailheadina67 Official Nailheader

    You may find that a smaller pulley will only help it run cooler at idle. Heating up at highway speeeds is a characteristic of Nailheads. Mine has always done that. In the past I had tried a 4 row radiator and it seemed to help but it was a cheesey core and only lasted a few years before it started leaking, and I replaced it with a 3 row. It tends to run hot but has never overheated on the highway, it just gets hotter at highway speeds.

    It has been said that the water pump with 3 blades will help as opposed to the 5 blade impeller. This is b/c it will keep the coolant in the radiator longer as it doesn't flow as fast. My thought on that is with a 3 blade pump, you would sacrifice cooling at idle speeds.

    To answer your question, to the best of my knowledge, the only smaller pulley that will fit is from a Nailhead a/c car, although the bolt circle size is the same as some fords and others, but the backspacing may be wrong.

    I found a nice 7 blade fan that seemed to help a little. Sometimes an oversized bore will cause this problem. Are you running a shroud? :Do No:
     
  3. Nick32vic

    Nick32vic Well-Known Member

    Ok, heres the break down.

    '65 425
    Apparently bored .30 over
    Kenny Bell cam and stall converter
    6 Stromberg 97 carbs running on the back 4 on a Weiand Drag Star Intake
    Mechanical fan and electric fan behind a Walker radiator.
    Fan shroud.

    Driving around town it doesnt get hot. As soon as we take it on the highway the temperature rises. We drove it highway speed for about 2 miles and it boiled over. I dont think it will over heat if its only driven around town at 25-30 mph.

    <img src="http://img.photobucket.com/albums/v298/NIck32vic/Cockroach/April%2022%202007/roadster2.jpg">

    <img src="http://img.photobucket.com/albums/v298/NIck32vic/Cockroach/April%2022%202007/2263.jpg">
     
  4. doc

    doc Well-Known Member

    Did I discuss with you getting a smaller pulley from me at one time about a month or so ago???????
    Any way , I have a 3 groove pulley sitting on my desk here that I will sell for $10 plus shipping. It is sand blasted and painted satim black, with no dings or dents. Measures 2 1/4'' deep by 5 1/8'' dia.
    It came off of a factory air 1966 425 in a Riv.
    Let me know if you want it.
     
  5. nailheadina67

    nailheadina67 Official Nailheader

    Perhaps that's the problem.........the electric fan may be restricting the air flow. I'd try removing one or the other and just using one fan. :Smarty:
     
  6. Nick32vic

    Nick32vic Well-Known Member

    When the motor was built thats when the problem started. The previous owners actually put the fan on to try and fix. It didnt make it better or worse so they left it on. We thought the bottom hose was sucking shut so i fixed that. No dice.

    Heres what we are planning on doing
    Put a 180 thermostat in it just so we KNOW its a 180
    put a smaller pulley on it
    Then start looking into carbs/jets and timing.

    Any other ideas?

    Doc, I dont think that was me. Let me see how big this one is though and Ill get back to ya.
     
  7. nailheadina67

    nailheadina67 Official Nailheader

    Maybe your radiator is too small......not enough BTUs. That pulley does look like it's too big. How is it on cool days?:Do No:
     
  8. nailheadina67

    nailheadina67 Official Nailheader

    Oh........and by the way.......THAT IS ONE SWEEEEET MOTOR!:TU:
     
  9. Nick32vic

    Nick32vic Well-Known Member

    No difference on cool days. It kind of perplexes that the builders/previous owners of this car didnt get it fixed. This is the second car we have that they built and this is the first thing we found that hasnt been as good or better than we would have done it. Every single thing they did was nearly perfect. Its a walker radiator and im sure they didnt just buy a radiator willy nilly. Its probably the right one. I could be wrong though. I guess im just wishing for an easy fix.
     
  10. nailheadina67

    nailheadina67 Official Nailheader

    You were posting as I was editing my post.........that pulley looks way too big to me. Excuse me, I'm on a dial up.:pp
     
  11. doc

    doc Well-Known Member

    Is your rad a 3 core or a 4 core????? IMHO, nothing less than a 4 core will work. A good clean 4 core+ shroud+ good 7 blade flex fan or electric and a 160 deg. thermostat in that car, [think about it, There is a absolute point on the high side that you hit like a brick wall. [the boiling point] the further you can get away from that point and keep the engine in operating temp. the better off you are. It is a lot easier for the rad to shed heat starting from 160 d. than 180 d. The hotter the coolant is to start with the longer it will take for it to cool down going thru the rad.If the heat aint there to start with it dont have to be dumped. A flex fan will be noisy at idle, but will move a ton of air thru the rad. But the car doesnt over heat at low speeds, it heats up at high speeds. So, there are things that will cause heating at high speeds, poor coolant circulation, some say an over bore will, but within reason it usually doesnt. I would get a shop to put the ''sniffer'' on it to see if there is combustion gas in the cooling system.
    Putting a smaller pully will give the water pump more force and also speed up the fan rpms increasing both coolant flow and air flow thru the rad. at the same time. A water pump doesnt '' pump'' it just moves the coolant around kind of like swishing your hand around in the bath tub. It is not a positive displacement pump. Another thing that can be done is to tack weld a disc to the back side of the water pump impeller to stop cavitation and give it a more positive force. I did that on my jeep and it hasnt run hot since. Make the disc the same dia as the impeller and about .035 or so thick. You dont want it to rub the timing gear cover after it heats up.
    A fan shroud is a must, and the fan has to stick at least 1'' inside the shroud with no more than 3/4'' clearance between the blade tips and the shroud.
    If the car has no shroud the fan has to be within 3/4 in of the rad all the way around to be effective.
    A fan will cool the engine up to about 40 mph and after that the effect begins to drop off.
    How ever in a open roadster like your car the engine is shedding heat all the time at a greater rate than a car with fenders and a hood covering it.
    Make shure the pressure cap and system is really working and not just look like it works. you need 14- 18 lb. of pressure to lower the boiling point.
    I once drove a ford over 300 miles with it showing 230 deg. on the guage. BUT it was keeping coolant in the system. the engine was not damaged. As long as the engine keeps coolant in the system it wont do a whole lot of damage.
     

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