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Projects Building My 34 B'Ville Coupe With a Potvin

Discussion in 'The Hokey Ass Message Board' started by N49racer, Aug 11, 2020.

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  1. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    Hi All
    I'm in the process of building a 354 Hemi with a Potvin setup for the street. I'm looking for anybody that has ACTUALLY BUILT an early Hemi with a Potvin Supercharger setup. I have some questions. If this is the wrong venue, I apologize and you can set me straight.

    ted
     
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  2. Deuces
    Joined: Nov 3, 2009
    Posts: 23,753

    Deuces

    Bump for a hamb member
     
  3. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    Just remember that you can only get a 1:1 drive ratio.

    Also, what the heck is long enough to fit this in? Got any pictures?
     
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  4. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    I know it has been done. I want to see HIS car.
     
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  5. PotvinV8
    Joined: Mar 30, 2009
    Posts: 408

    PotvinV8
    Member

    What are your questions? I have experience with the setup.
     
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  6. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    How much has been cut off the end of the crank.
     
  7. MUST. SEE. PICS.
     
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  8. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    I race at Bonneville so I thought i would build a 34 5 window in the 50s salt racer style. Then I happened on a picture of a Potvin. The length is 44 inches which should fit with some massaging. I'll look at starting a build thread as it's going to be a journey. DSC05400.JPG DSC05401.JPG DSC05402.JPG
     
  9. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    I forgot to address the 1:1 ratio. The 1:1 works out great for my 415 Hemi. Chico at Moon Eyes runs a roadster on the salt with one of his Potvin setups on a SBC, it is overdriven. He told me it was a drive off of some GMC truck thing that fit inside the Potvin cover.

    cheers
    ted
    I have the body and frame currently but have not started on it yet. Accumulating pieces.
    IMG_0843.JPG
     
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  10. You might want to plan for some sort of harmonic balancer or degreed timing wheel that spins off the end of the driven rotor in the 6/71 since there is no access to the balancer area at the front of the motor. I guess the guys who ran them will chime in soon. They may have run a degreed flywheel and a hole in the bell housing. Probably not too practical for street driving and tuning. As you said, "it's going to be a journey". Watching
     
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  11. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    The

    The only REAL worry I have is the longevity of the drive system. I put some miles on my cars and it must be reliable. I will be running a gear drive setup as I don't think the double chain drive with a slip fit on the crank will do it. Getting a timing mark is fairly easy as I should only need a TDC mark for reference. I'm will be running a pulley for the gen off the front end of the top rotor. Not having a balance is a concern. Then there's the lubrication thing, and the injection thing and oh it's going to be a bumpy journey.
    Building a Hot Rod or a Race Car is just a bunch of problem solving exercises.


    ted
     
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  12. gimpyshotrods
    Joined: May 20, 2009
    Posts: 23,264

    gimpyshotrods
    ALLIANCE MEMBER

    I dig the offbeat stuff.

    I am building a mid-engine blown Hemi Model A pickup.
     
  13. You got this Ted. Any plans on coming back to the Salt?
     
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  14. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    If the order was open , we would be there
     
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  15. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    Last year we only put 2 passes on the car because of the poor salt. We changed the oil and it ready to race but here we sit listening to it on the internet
     
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  16. PotvinV8
    Joined: Mar 30, 2009
    Posts: 408

    PotvinV8
    Member

    You mentioned running a gear drive setup so I assume this info is moot as it would be dependent on the method in which one couples the crank to the blower rotor.

    Chico's setup was fabricated by Fred Larsen back when he ran that engine in his streamliner so I'm sure it's a mix and match of parts from the day.

    The chain drive coupler that is employed on most Potvin setups is designed to be the weak link in the system in case there is a backfire, cough, sputter, spurt, etc through the blower. The chain is designed as the shear point to keep the damage to a minimum if the speed between the blower's rotor and the crank change significantly. Just something to consider regarding street use and a gear drive.

    Timing, as mentioned, can be marked and measured off the flywheel, that's how my setup is and Chico's as well.

    Not sure your concern regarding the "lubrication thing" as the blower is treated just the same as any other top mounted 6-71 setup in that the bearings are sealed.

    Fueling is a concern as there is a lot of real estate between the hat and the intake valves which can cause all kinds of fun, especially on a mechanical setup.

    You mention running a pulley off the blower for the generator, which isn't a problem on its face, so long as you're not planning on using a Hilborn-type fuel pump as this would typically be driven off the front of the blower.

    Good luck, have fun, and keep us posted!!!
     
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  17. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    Thank You for the input.
    I decided to go with the gear drive as opposed to the slip fit chain as I believe the slip fit and the key ways would not last as the pulses from the blower and the engine would cause them to wreck the crank fairly quickly. The backfires (if any) should be taken care of by good BOV system. Making it look 50ish may be an issue but i think putting the BOV up by the manifold would help.

    The lubrication for the bearings is easy with sealed bearings. I'm wondering if the gears will get enough splash or a trough might be needed to direct more oil to the gears.

    For the fuel, i'm thinking of running efi UGH and hiding it under the manifolds as I will be casting the manifolds myself and will make them a little taller than the Potvin ones. It's not authentic but there has to be some trade offs to get reliability.

    No, i'm not thinking of running MFI as I want this to reliable. Running carbs on the intake to the blower looks to me to be a pain unless I want to use some kind of primer system.

    ted
     
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  18. PotvinV8
    Joined: Mar 30, 2009
    Posts: 408

    PotvinV8
    Member

    That's how my SBC Potvin is setup, injectors under the manifold. Hopefully it won't turn into a large fuel bomb if they ever leak. Might consider putting a little fuel through the blower as well just to keep things cool.
     
  19. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    Is yours for the street? are you running the chain coupler? I was thinking of putting mine on a dyno to run it in and hopefully work the bugs out before driving it. Glad someone else is going the efi route. When I mentioned it I was waiting for the shit storm :) Do you you need to cut the crank off on the SBC? If I don't have a bolt in the end of the crank or the bolt holding the gear on the rotor, i end up with 1/16 clearance.
     
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  20. PotvinV8
    Joined: Mar 30, 2009
    Posts: 408

    PotvinV8
    Member

    Street, yes. Chain coupler, yes. Dyno is key for tuning and figuring things out. Didn't need to cut anything on the SBC, it all slipped together nicely. How are you measuring the distance between the crank and rotor with the blower/timing cover adapter installed?
     
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  21. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    If I take off the front main cap I can get in there with a mirror. I knew it was going to be tight by using measurements.
     
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  22. PotvinV8
    Joined: Mar 30, 2009
    Posts: 408

    PotvinV8
    Member

    I'm sure you've already thought of this, but I would measure it like you do a bellhousing/clutch/trans setup to achieve hydraulic throw out bearing specs.

    Measure the stick out of the crank against the timing cover flange and do the same on the blower from the rotor to the mounting surface of the timing cover adapter. Should get you really close. But you've probably already done this...
     
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  23. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    Yeah, I came up with 3/4 inch minimum I need to cut off. I think I was just looking for someone else that had hacked the end off their new 1/2 inch stroker crank. Yaknow at least I wouldn't be the only idiot out there.
    :(:(;)
     
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  24. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    well if there isn't anyone else I guess I'll be the first. It only hurt for a a while. Boy, this better work
    DSC05413.JPG DSC05414.JPG
     
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  25. RatPwrd
    Joined: Apr 15, 2019
    Posts: 235

    RatPwrd
    Member
    1. 37-38 Chevys

    MAN!! that definitely falls under "measure twice cut once" and hopefully not "cut it twice and its still too short!"
     
  26. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,672

    Jmountainjr
    ALLIANCE MEMBER

    What is your plan for cutting the crank snout?
     
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  27. I think he already did from the looks of it.
     
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  28. N49racer
    Joined: Aug 26, 2012
    Posts: 94

    N49racer
    Member

    A big cut off wheel and a deep breath and there it was. luckily it didn't need to be that accurate as once the hub is on there is just a washer and bolt like original.
     
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  29. JC Sparks
    Joined: Dec 8, 2008
    Posts: 733

    JC Sparks
    Member
    from Ohio

    [QUOTE="N49racer, Yaknow at least I wouldn't be the only idiot out there.
    :(:(;)[/QUOTE]
    You will never have to worry about being the only idiot out there. We are all there with you.
     
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