Chapter 2. Missing at part throttle.

[drolston]

I am going to get this old flathead purring like a kitten if it takes me a year! Which I am well into.

On my recent "Missing at full throttle" post, you helped me fix that problem. Turns out two ignition wires had gone open circuit. They would jump the gap and run fine at low rpm but give out at high rpm. Now it revs right up to 5,000 rpm without missing a beat. Until it starts starving for fuel and losing power. I turned the fuel pressure up from 2.5 to 3.0 psi and that helped a little but not completely. Pulled the top off of the center carb (97) and found that the float was set way low; like almost 3/4 inch. I reset to a shade under 1/2 inch. Will road test that fix soon.

But another problem has shown up. The engine idles perfectly but runs rough as I slightly open the throttle from idle to about 1,500 rpm. Above which it smooths out. Smooth at idle and high rpm pretty much rules out ignition:

- Except that in trouble shooting the full throttle problem I replaced the Pertronix distributor with a rebuilt points distributor. For whatever reason, the Pertronix distributor had a lot (like five turns) of vacuum brake; the points distributor is set with the brake having a very light drag. Could too much advance too early cause the low rpm stumble. I have the advance setting advanced 3 degrees, which is what ran fine on the Pertronix.

Any suggestions?