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Technical Flathead belt misalignment

Discussion in 'Traditional Hot Rods' started by HaroldDegand, Apr 17, 2021.

  1. Hi, my plan is to put a french flat in my original '32 chassis, using '32 engine mounts.
    No worry about firewall, my question is about the alignment of the pulleys.

    I put new 8RT waterpumps from Speedway to run single belt system, probably with an electric fan.

    I have a misalignment between the pump and the crank pulley.
    The pumps are about 4mm (1/6") more toward the engine.

    I'll also need to change the gen, french flats runs 24v system.

    My options are :

    1 - machine the crank pulley and get it 1/6" more toward, but the belt stay close the distributor and the engine mounts,
    2 - press the waterpump pulleys out, put a washer and press back on, the belt is a little bit far away the dizzy. Is there a risk of damaging the pulleys during the operation ?
    3 - nothing to do, it's not so bad

    What's your opinion ?



  2. I might be wrong,,,,but I believe you have a mismatch of parts you are trying to use .
    I wouldn’t try pressing the pulleys out any,,,,,and I’m pretty sure that the parts you are using requires you to run two belts .
    I’m sure more talented eyes will chime in here soon .
    Good luck .

  3. shorrock
    Joined: Oct 23, 2020
    Posts: 60


    Had the same problem, put the pumps into my lathe and cut through the pulleys. They are quite fragile. The rest of pulley center was then machined off the shaft. Inserted new centers, silversoldered them, machined to 0,025mm undersize the shaft diameter and refitted the pulleys to their new location. You will probably not be able to pull the pulley without destroying it as the are very tight. On my 34 I had to make the crank pulley as well as I could not run it the way it was. This time I made a new pulley, machined the old one off and pressed the new one on the remaining slotted tube .
  4. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,308

    from Quincy, IL


    Several years ago i wanted to use new 8RT single belt pumps on a dual belt engine to gain the integrated engine mount arms of the 8RT pump. That required replacing the pump’s wide belt sheave pulley with narrow belt versions.

    The first pulley I attempted to press off the pump, shattered. I then made a two piece support sleeve/fixture, held together with a hose clamp, that pressed against the pulley hub inside the pulley, instead of the sheave taking the force. That worked nicely and I harvested some narrow belt pulleys from used Mercury 8CM pumps.

    So far so good. However, it turned out that one of the narrow belt pulleys shaft bore was too big and was not a press fit on either new 8RT pump shaft. That pulley was bored out and fitted with a sleeve, also bored out a bit, to gain a press fit. Whew! lots of work to avoid modifying the motor mounts to adapt the different height of the Merc pump ‘arm’. Not to mention that any future pump replacement now required like modification. :confused:

    It would appear to me that you could possibly solve your problem by using a single sheave 8RT crank pulley designed to work with the pumps you have.

    rusty valley likes this.

  5. Thank you all for your replies.

    I don't want to damage the pumps. They are brand new and very long time for delivery (ordered begin December and received last week-end).
    Also, US parts are pretty difficult to find here in Europ.
    So the most simple, I believe, is to shave the back of the crank pulley about 1/8".
    This way it will go "deeper" in the engine. The misalignment will be 1mm (1/24") so pretty ridiculous.
    If replacing the crank pulley by a 8RT, do I need to change also the timing cover ?
    US timing cover do not accept french dizzy. Do you see what I mean.....
  6. Do you have the oil slinger installed?? On US motors there should be a bushing installed on the crank snub that spaces the pulley and it has grooves machined in it to push the oil back into the motor. You can add shims or remove material accordingly to the bushing to gain the proper alignment.

    Last edited: Apr 17, 2021
  7. Yes, I'm pretty sure there is an oil slinger.
    The machined groove is directly on my crank pulley.
    I bought an offenhauser one piece oil seal to replace the front cork seal, so whatever, my pulley must be machined.
  8. solidaxle
    Joined: Jan 6, 2011
    Posts: 605

    from Upstate,NY

    If it were mine and the crank pulley was correctly installed and the generator pulley lines up. I would relocate the water pump pulleys. I'll just caution you, do not put pressure or a puller on the pulley's they are prone to break, you need to press the shaft.
  9. gary macdonald
    Joined: Jan 18, 2021
    Posts: 236

    gary macdonald

    Double groove crank , one goes inside and the pump to gen one goes outside to pump and fan . One fanbelt didnt go around both water pumps . One belt for pump and fan one belt for gen and pump
    walter likes this.
  10. Flathead Dave
    Joined: Mar 21, 2014
    Posts: 3,736

    Flathead Dave
    from So. Cal.

    Get a single belt crank pulley.
    I went from a 2 belt pulley system to a single. I replaced my 8BA sedan water pumps with 8RT pumps and then replaced the crank pulley with a single pulley.
    Last edited: Apr 17, 2021
    Hnstray likes this.
  11. Hnstray
    Joined: Aug 23, 2009
    Posts: 12,308

    from Quincy, IL

    Crank pulley ‘should’ be an easy swap ...... depends whether or not the pulley snouts are the same diameter on French vs US production.

  12. alchemy
    Joined: Sep 27, 2002
    Posts: 18,291


    Do you expect the stock front crossmember to clear that late model pulley? You might want to do some measuring there before you get too far into this project.
    Flathead Dave likes this.
  13. Yes, that's right but on a french flat, the fan is too far away forward and there is no room to use it. It is litterally in the radiator.
    I didn't re-use the original pumps because they are very ugly.
    As I said, I have to replace the original gen by a 12v one. So I can align it as I want.
    Yes, of course I did ! The crossmember was modified and there is room enough for the french dual groove pulley.
  14. Maybe it's easier to see the difference between the 2 pumps like this :


    I put a 3mm (1/8") sheet metal under the new one, now it lines with the old one :

  15. gary macdonald
    Joined: Jan 18, 2021
    Posts: 236

    gary macdonald

    Got it , understand now .

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