why is the fuel pump eccentric so large on TA roller cams

Discussion in 'Street/strip 400/430/455' started by GranSportSedan, Jun 25, 2017.

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  1. GranSportSedan

    GranSportSedan Guest

    I have a TA solid flat tappet Cam and a TA billet roller cam and for some reason the fuel pump eccentric on the roller cam is huge in comparison. why did they do this? roller cam pic.png
     
    GranSportSedan, Jun 25, 2017
    #1
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Good question, I do not know, I believe the solution is to space the stock pump out a bit. The CV pump I use doesn't require that. The big eccentric strokes the pump near 100%. I believe JW measured all of this with a cutaway timing cover years ago.
     
    LARRY70GS, Jun 26, 2017
    #2
  3. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Here is Jim's comments on the CV pump from my original Engine build thread.

    http://www.v8buick.com/index.php?th...totype-specs-and-testing-larrys-motor.221289/


    "During the build I cut up an old timing cover, to check the fit of my Billet fuel pump, with the larger eccentric of the roller cam. Since my pump has only light contact with the cast cam of a stocker at minimum stroke, and has extended stroke capability, it fits perfectly with the bigger eccentric. Even with the wear arm in place. Here you can see I still have stroke available, even at full lift of the cam."

    [​IMG]

    [​IMG]

    "if you have ever wondered where the timing chain is close to the pump arm, here's the pic.."

    [​IMG]
     
    Last edited: Jun 26, 2017
    LARRY70GS, Jun 26, 2017
    #3
  4. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Here is page 65 of the current TA Catalog. See the note at the bottom. TACatalogPg65RollerCams.JPG
     
    LARRY70GS, Jun 26, 2017
    #4
  5. Briz

    Briz Founders Club Member

    My roller did not have an eccentric for the fuel pump.
     
    Briz, Jun 26, 2017
    #5
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yes, but all of TA's hydraulic rollers do.
     
    LARRY70GS, Jun 26, 2017
    #6
  7. Briz

    Briz Founders Club Member

    Maybe thats the difference. My cam ,Bought from Michael Garrison, is a solid roller.
     
    Briz, Jun 26, 2017
    #7
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Yes.
     
    LARRY70GS, Jun 26, 2017
    #8
  9. GranSportSedan

    GranSportSedan Guest

    i'm just wondering why they didn't make the eccentric the normal size. my cam is a blank so I could go solid or hydraulic with it. my plan of course is hydraulic since I already bought the solid gold hydraulic roller lifters
     
    GranSportSedan, Jun 26, 2017
    #9
  10. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    I'm curious as to why myself. I guess we will have to wait until Mike T or JW sees this.
     
    LARRY70GS, Jun 26, 2017
    #10
    GranSportSedan likes this.
  11. Jim Weise

    Jim Weise EFI/DIS 482

    I asked Mike this, and I guess it was a fight just to get the core manufacturer to put any fuel pump lobe on it at all. They did not want to do it for some reason. I think it was a "take whatever we can get" type situation.

    JW
     
    Jim Weise, Jun 27, 2017
    #11
  12. guyver002

    guyver002 Well-Known Member

    I can't help but think looking at the side by side. The larger profile definitly looks like it would actuate the pump arm sooner then push it further for an even deeper suction stroke and then close a little later. It's just my theory, but maybe it was to get a little more out of the stage 1 pumps they assumed most of their customers were running. With the excellent power and torque bump a roller would give perhaps they just wanted that little extra safty margin since I have read the stage pump can only support so much horse power before things get dicey with adequate fuel flow.
     
    guyver002, Jun 27, 2017
    #12
  13. Bluzilla

    Bluzilla a.k.a. "THE DOCTOR"

    I may be looking at this wrong but isn't the oem cam made with that section of the cam gear flange notched to counter balance the offset eccentric? I don't see any such thing on the roller core. One would think that there would be unwanted harmonics going on there, even though it's spinning half the speed of the crankshaft. Just a thought.

    Larry
     
    Bluzilla, Jun 27, 2017
    #13
  14. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    That would make sense. I looked at pictures of other roller cams with eccentrics, and didn't see anything like that though.

    https://www.google.com/search?q=roller+cam+pictures&tbm=isch&imgil=S_92Gf_z-084WM%3A%3BR96h_dCQUvtlSM%3Bhttp%253A%252F%252Fphotobucket.com%252Fimages%252Froller%25252520cam&source=iu&pf=m&fir=S_92Gf_z-084WM%3A%2CR96h_dCQUvtlSM%2C_&usg=__RVIRlGeSVYge6pT9XPlY3iet4yA=&biw=1280&bih=891&ved=0ahUKEwiz47nQ-t7UAhULVj4KHQmpAdMQyjcIPw&ei=k8xSWfPNAYus-QGJ0oaYDQ#imgrc=0mQfyt0QkQqAtM:

    Maybe it is balanced in other ways? I don't notice any vibration or roughness with my engine, it's very smooth.
     
    Last edited: Jun 27, 2017
    LARRY70GS, Jun 27, 2017
    #14
  15. GranSportSedan

    GranSportSedan Guest

    I just figured the flat spot was to keep it from rolling off the table. :)

    Since my cam hasn't been ground yet I wonder if they could reduce the fuel pump eccentric size when it's ground ?
     
    GranSportSedan, Jun 27, 2017
    #15
  16. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    What is your HP goal with your engine, and what pump were you planning on using?
     
    LARRY70GS, Jun 27, 2017
    #16
  17. GranSportSedan

    GranSportSedan Guest

    500-550 stock appearing hp, I have a RobbMC pump
     
    GranSportSedan, Jun 27, 2017
    #17
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Maybe the RobbMc pump won't mind the big eccentric. The CV pump doesn't. I wonder if JW ever tested a RobbMc pump with a TA roller cam, or if someone out there is running that pump with the roller cam. You might not need to reduce the size of the eccentric, especially if it gives you more stroke like the CV pump does.

    Maybe Jim can do some tests with his cutaway timing cover?
     
    Last edited: Jun 27, 2017
    LARRY70GS, Jun 27, 2017
    #18
  19. chrisg

    chrisg Silver Level contributor

    I've been running the RobbMc pump with a TA roller for over a year with no problems.
     
    chrisg, Jul 9, 2017
    #19
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Well, there you go, the big eccentric is not a problem unless you want to run a stock fuel pump, and if so, all you need to do is space the pump out and make sure there is no wear plate on the arm. I think most of the pumps come that way these days anyway.
     
    LARRY70GS, Jul 9, 2017
    #20
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