coil, condenser or points?

[chilly1]

I have a miss on my 1971 55 hp chrysler 557 hc. The parts are $$ and I want to save $$. It starts flawlessly and sounds good until I run it for a few minutes at part throttle, then when I bring it down it misses. Both plug wires cause worse running when removed. Is any one piece of this ignition system more prone to problems?

Thanks!
Cheapskate Joe (LOL)

 

[Frank Acampora]

Re: coil, condenser or points?

Well, Joe, I can not cross reference model numbers with ignition so I will take your word that you do not have electronic ignition. With either magneto ignition or points and coil battery ignition, the points must be clean and gapped to .020. Both sets must be equal gap or the timing between cylinders will be different.

Since with either ignition system, the spark is weakest at slow speeds, it would be normal to see improperly set points or dirty ones to cause slow speed running problems.

Timing set too retarded will also cause low speed running problems. The engine will generally start well because you are most likely setting it to start/fast idle position. Worse running when you remove either plug wire shows that both are firing.

But let us not forget that reducing the idle speed too low will also lead to missing or stalling. It may sound fast to the ear and it is difficult to set by ear, so a tach is really a necessary instrument on any boat, but, idle speed should be around 1000 RPM in neutral and 700-750 in gear, in the water.

 

[chilly1]

Re: coil, condenser or points?

Thanks, Frank! I see I need to read more. I am not sure how to adjust idle speed, but I know about the timing. I do not think I have a start/fast idle speed position. I also have no tach. I DO have to give it part throttle or it will die. I was very thorough with the points, but they could be dirty again.

Question: My mag plate says .020 gap, and the Chrysler Crew guy says .015.
Would .015 change anything in a good way for me?

I also have a brown plug on top, and a wetter blacker one on bottom. Half of the bottom electrode is still white.