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Technical Rochester 2g question

Discussion in 'The Hokey Ass Message Board' started by Pass The Torch, Sep 4, 2020.

  1. Pass The Torch
    Joined: May 18, 2018
    Posts: 566

    Pass The Torch
    ALLIANCE MEMBER

    Here's the skinny: 283 Tri-Power. Starting the car, no issue. Let it run, idle, no issue(s). Drive it around, or let it get good and warm, and the idle slowly drops, and engine dies. Been playing with this for a few weeks, and finally decided to dig in and figure this out.

    When the problem happens, and the engine dies, (or I shut it off) I can see fuel pouring down the barrel(s), and on the intake from the center (primary) carb. Took it off and apart, and verified that the gaskets are good and all the assembly screws are tight; put it all back together and still does it.

    Thinking I have a hairline crack somewhere on the body or bowl that obviously gets worse and shows itself with enough engine heat. Thoughts / suggestions? Any way to bench test to confirm?
     
  2. saltflats
    Joined: Aug 14, 2007
    Posts: 10,313

    saltflats
    Member
    from Missouri

    What's the fuel pressure?
     
    wraymen likes this.
  3. Pass The Torch
    Joined: May 18, 2018
    Posts: 566

    Pass The Torch
    ALLIANCE MEMBER

    Pressure is at 10 or so. Facet pump, with regulator. I should mention that this is not a new set up; It's been on the car for many years; driven trouble free for the last year and a half after an engine rebuild, including round trip to Louisville last year with the exact same set up - nothing has been changed, save for air and fuel filters. The issue had only been in the last few months or so, again, once she's good and hot.
     
  4. 41rodderz
    Joined: Sep 27, 2010
    Posts: 5,198

    41rodderz
    Member
    from Oregon

    You can have cracks develop from over tightening screws/fittings . You said the gaskets are good but that is not going to help if the surfaces are warped. Check that out.
     

  5. Rusty O'Toole
    Joined: Sep 17, 2006
    Posts: 9,297

    Rusty O'Toole
    Member

    10PSI fuel pressure way too high
     
    egads, scrappybunch, wraymen and 3 others like this.
  6. Kevin Ardinger
    Joined: Aug 31, 2019
    Posts: 231

    Kevin Ardinger

    Is the float heavy? Possibly something under the needle and seat? Had the same problem with one of my secondary carbs. Carbs were out of the box from an unnamed Rochester guru, and one float was set way off. About the only thing that can do that is a issue with the float or the needle and seat.
    10 psi is way too much by the way. 4-6 should be plenty

    Sent from my iPad using The H.A.M.B. mobile app
     
    X-cpe likes this.
  7. Almostdone
    Joined: Dec 19, 2019
    Posts: 312

    Almostdone
    Member

    Agree with O’Toole. Drop that pressure to 4 or less and might solve your problem. May need to replace the needle and seat as well, since that’s what the fuel is pushing past. The 2Gs want a fuel pressure of 4 psi or less.
     
    Blues4U likes this.
  8. Blake 27
    Joined: Apr 10, 2016
    Posts: 659

    Blake 27

    Don't overlook a fuel percolation issue.
     
  9. Bob Lowry
    Joined: Jan 19, 2020
    Posts: 221

    Bob Lowry

    Whenever I have a new issue that I didn't have before, I retrace my steps to see what I did last before it happened.
    Perhaps a piece of dirt was dislodged when you switched the filter, or a piece of hose got loose and inside the
    needle and seat. My guess would be to go back to the needle and seat, make sure that is seals completely when
    you turn it upside down and blow into the inlet, and check the float for any gas inside. Most likely not the float
    as it doesn't happen all of the time. If you have been running that fuel pressure all this time with no issues, it
    could be that it is too high and finally getting past the seat. I typically set mine at 4.5 lbs. Let us know what you find out.
     
  10. Pass The Torch
    Joined: May 18, 2018
    Posts: 566

    Pass The Torch
    ALLIANCE MEMBER

    With regards to PSI - That's how it had been set before I acquired the car; and it ran trouble free until recently. Not saying it isn't too high, more that this isn't something I came up with and had trouble right off the bat.

    Needle and seat - wouldn't that give trouble regardless of engine temp.? Just asking.

    I'll drop the PSI and see what she does.

    Percolation - nothing new to cause that issue out of the blue. The way the lines and everything are located have been that way, unchanged, since 1980, give or take. Haven't touched a thing.
     
  11. Mine are at 4 1/2 lbs on a recent rebuild and run great. 4 barrel Holley’s don’t like much over 6-7, 10 is a bunch. Are you sure your at 10 lbs.? Good working gauge?
     
  12. Pass The Torch
    Joined: May 18, 2018
    Posts: 566

    Pass The Torch
    ALLIANCE MEMBER

    Backed it down to 5 to see what it did; seems to have done the trick. I've not touched it since I took over the car about 2 1/2 years ago, (that's where it was set) and drove it quite often since the engine rebuild last Spring; I guess she finally decided it was too much pressure. No idea why it was set that high, and the only person to ask is no longer with us...

    Thanks to those that chimed in.
     
    Almostdone, cactus1 and wraymen like this.
  13. hudson48
    Joined: Oct 16, 2007
    Posts: 2,642

    hudson48
    Member

    I have tripower on my 327 and had the same issue. Your fuel pressure is too high. 4-5lbs is all you need.

     
    egads likes this.

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