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286 Merc Flathead, 3 x 97's Need Help!

Discussion in 'The Hokey Ass Message Board' started by Psychobilly Boi, Sep 21, 2010.

  1. This is on my list of things to try. I'll buy a timing light as its a pretty good thing to have anyway! I'll see how the spark looks on each lead.

    I also have a mutimetre so I'm going to check resistance from the brass button on the inside of the dizzy cap to the spark plug terminal to ensure there is no break in the curcuit from cap to plug.

    I've got new points as well so I'll replace them the current ones look suspect.

    I'm using Bosch but I've heard the Champion plugs are having massive issues.
  2. Adam F
    Joined: Jun 19, 2001
    Posts: 323

    Adam F

    Hey Dan,

    Here is my list of ideas-

    Install new condenser- especially if you’ve been fedding 12v to it all the time!

    Install ballast resistor - this goes in the hot wire from the coil to the dizzy - then check points – as I mentioned the other day if you’ve been running them to hot they can ark and burn out.

    Check the post on the distributor that the hot wire attaches to is in good condition and that the insulation is intact- remember that time you guys had to come and push my car? The insulation on that little post had disintegrated and the distributor was grounding out, causing the motor to stop running.

    Leads- Leads leads! – As ugly as they are –I am currently running 8mm bosh rubber insulated leads – when I had cloth/vinyl wires with stick on ends I had problems with keeping the ends on the wires and stuck into the crab cap.

    I agree – the vacuum brake make be stuck on – stopping the dizzy from spinning up. I also had the leather pad fall out of the cam and get stuck in the weights once- motor didn’t run too good with that in the Dizzy ( actually happened at the front of the house after I had just driven 1600 kilometres! )

    Low battery? I chased my tail once with similar symptoms only to find that my battery was so low and my charging system was screwed. Have you had your on trickle charge?
  3. Updated with the latest findings on my original post.
  4. HeyyCharger
    Joined: Dec 8, 2008
    Posts: 941


    Bump for Phsycho!!

  5. Updated again on my first post.
    Joined: Jun 6, 2005
    Posts: 1,887

    Member Emeritus

    I'm just jumping in because this post was interesting. After reading thru everything the continual loss of valve adjustment needs to be resolved but after reading all the other posts , I dont think that addressing ignition as an issue is the problem. Bogging down and popping in your words to me means running out of fuel during acceleration. The three carbs oppening up at once to me produce a lean mixture. You didnt indicate the carb jetting and I don't know if you have ethanol base fuels but I would suggest that you richen up the jetting in the carbs two to four points to get a richer off idle response. Increasing the fuel pressure will not increase the fuel flow thru the jets so dont bother with that. These are my thoughts.
  7. BLAKE
    Joined: Aug 10, 2002
    Posts: 2,776


    Lots of info here, so apologize if this has been covered - I'd replace that dial-type regulator with a good Holley unit.

    My 8BA with 3 x 97's did the same thing after I rebuilt/re-jetted the carbs and installed the dial-type regulator set to 2.5 lbs. I did some digging and lots of folks report problems with these regulators. I replaced the regulator and set the Holley unit to 2.5 lbs using a gauge... the problem was immediately gone and it's been fine for 4+ years.
  8. xadamx
    Joined: Apr 18, 2003
    Posts: 1,170


    Sounds like you've done everything but take the carbs off and check them thoroughly for clogs, blockages, crushed emulsion tubes, stuck bits, etc. It doesn't take long to rip into those. Good luck, and thanks for updating this post...I've been keeping an eye on it.
  9. Hi Dick, great to hear from you mate.

    From my reasoning I had to start somewhere and ignition with my limited technical knowledge was a good a place as any. At least now I have accomplished two things. I have a much much better understanding of my ignition system and I've eliminated 98% of the ignition system as a cause of the issue. Next stop carbs.

    My thought process, as basic as it may have been, was that without changing anything to so with the carbs it started running crap. So my mind started to think of probable causes which entailed things that have a tendancy to fail such as coils, condensors, spark plugs etc.

    I cant help but think that maybe two issues happened simultaniously sush as the lifters backing off/cam lobe failure and something to do with the carbs.

    But why would the carbs, which ran great at one stage suddenly produce a lean condition off idle. Im guessing that something has clogged one of the jets, idle circuit or off idle circuit.

    What I plan to try next - change the oil in the car and look for pieces of camshaft. Take the main jets out and examine for debris. I also have two block off plates so I can put these under two carbs and run the centre to check its operation as a single carb. I can swap each of the carbs into the centre position to check each in turn.

    Sound reasonable?

  10. Hi Blake,

    Good suggestion these dont exactly come with a brilliant reputation.

    However, I dont have another reg at the moment but I have a fuel pressure guage in the car and its at a constant 2.5psi so I'm assuming (maybe dangerious) that the fuel pressure is ok?

  11. Hi Adam,

    Unfortunatly that's the next step is taking apart the carbs making sure they are not blocked up with any debris or anything. I'm hesitant to take them apart as I dont know 97's at all and dont want to mess up what is an expensive set of carbs!

    This along with removing one other question that has been asked which is have a wiped a cam lobe (I'll be draining oil tonight to look for chunks).

    I have a jet wrench I can at least take the main jets out and look for signs of debris. I'm guessing taking out the fuel bowl plugs will allow the fuel to drain out (and take with it anything in the bottom of the bowl). Unlike 94's its impossible to see well into the bottom of the bowl with the float in the way!

  12. Updated on first page again.
  13. So does it only play up under load or is it also while stationary? Fuel pressure doesn't drop under acceleration at all? Just wondering if the fuel pump is on its way out, not pumping enough under acceleration.

    Either way its a nasty learning curve...
  14. Hi Devil,

    Its under load that I can see it most.

    Fuel pump is a new electric one.

  15. Hi Guys,

    Lots of crap in the bowls of the carbs, see my original post for the update.

  16. strombergs97
    Joined: May 22, 2006
    Posts: 1,888

    from California

    Hello..Take them apart and check the emulsion tubs to make sure they are not plugged, the small air holes on the side of the tubes. Blow them out to make sure "NO" residue or contaminates. Is that rust particals, if so maybe from you tank..
    Check the power valves also for particals..CLEAN...CLEAN... CLEAN..
  17. As Strombergs said clean clean clean. Obviously got that shit blocking up the carbs and restricting the fuel flow...
  18. Updated main post.
  19. andyg
    Joined: Aug 10, 2007
    Posts: 560


    I know it may be too late for this advice and maybe you've already done it but....

    you got to find out where that stuff is coming from or you'll be tearing into those carbs again shortly! a good filter as close to the carbs as possible but on the tank side of the pressure gauge will work temperarily but not for long.

    it's awesome to see you've went through the process and at least have a good suspect now. that's what it takes to keep 'em on the road! and sometime when it tanks out on you on the side of the road you'll be better able to find the problem!

    thanks so much for keeping this updated. it helps us all learn.
  20. dodored
    Joined: Feb 5, 2007
    Posts: 640

    from Concord NC

    Having similar issues with my flathead. I installed a PCV valve under the intake in the plenum to relieve some pressure, but I suspect that has caused more issues than it solved. Keep us posted.

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