1912Minerva Posted November 15, 2015 Share Posted November 15, 2015 Hi All, For the Model 20 owners - I am wondering what type of spark plugs you are using and what gaps you are running? My car idles at low revs beautifully but hesitates badly under acceleration and I am trying to narrow down the cause. One of my suspects is the plugs. I am running an NH Holley carby (from T Model Ford) as I don't have a Breeze and the bottom section of my inlet manifold has been cut off at some stage. The fuel delivery line had a big U-bend in it before arriving at the carby and this was eliminated today by re directing and modifying the line so it now has a fairly steady fall from tank to carby with no "uphills" - this definitely seems to help but it still hesitates under acceleration (whether it be idling or actually driving). I also wondering if a magneto refurbish is also on the cards... Cheers, Andrew. Link to comment Share on other sites More sharing options...
MochetVelo Posted November 16, 2015 Share Posted November 16, 2015 Your fuel flow is easily checked by disconnecting the fuel at the carburetor. If you get a steady flow, it is OK. You can check your intake manifold tightness by playing an unlit propane torch along the connections. Increased motor speed indicates a leak. A magneto rebuild is always a good idea. It eliminates a potential cause of trouble. Phil Link to comment Share on other sites More sharing options...
trimacar Posted November 16, 2015 Share Posted November 16, 2015 I doubt it's the spark plugs causing the hesitation...I'd look at the carb first, what you're describing sounds like starving for fuel, and if it's not in a fuel line restriction, then it's in the carb....float set too low, size of jets not correct, and so forth...am not familiar with Holley carbs so don't know if they have any mechanism for an acceleration pump to add additional gas...... Link to comment Share on other sites More sharing options...
1910Hupp Posted November 19, 2015 Share Posted November 19, 2015 I ran the NH prior to going back to the Breeze . The NH is a very simple carb and really there is nothing to adjust other than the mixture and Idle speed . The later won't effect your acceleration but the former might. Close it right up and openit 11/2 turns then open close/ until its running sweetly and that's it . The other thing is to check that the throttle at the carb is moving as it should sometimes if the linkage is not right when we depress the gas pedal the carb throttle hardly moves at.all . The major problem with the NH is that it is to big for the Hup engine as it was designed for the 2.3l of the Model T. Hence top end speed is great but smooth idle is a problem. You say you have a smooth idle which would be unusual in my experience with the NH on the Hup ? Inlet manifold leak The previous owner of my car converted the plugs to 18mm which I'm sure are non standard. I run Champion D21's (the hottest 18mm plug I could get) gapped to 23 thou Karl Link to comment Share on other sites More sharing options...
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