Coil resistance

[Dave Woodward]

Just trying to troubleshoot some rough running at c. 2,500 rpm and am replacing the coil in advance of Silverstone. It’s been running a Pertronix flamethrower 1.5 ohm. I have a replacement on order but not convinced it’s going to arrive before the weekend.

If I have a Lucas 3 ohm coil in the garage, will the difference in resistance cause me any issues??

[StewbieC]

Hi Dave, higher resistance normally means less power and less spark, high ohmage coils will also run cooler (and should last longer). The only caveat is to find out if the Lucas coil requires a ballast resistor or not and you may have to take the one out you may have. They are normally wired in series with the coil. Also if you have electronic ignition you need to work out if the coil is compatible. Sorry I can't be more help.

[Dave Woodward]

Replacement Flamethrower has just arrived

Anybody need a 3 ohm Lucas coil

[Dave Woodward]

A quick run out shows it’s still running rough between 2-3,000 rpm and surging a little on idle. It had started doing this before the engine came out. Since then, new dizzy cap, new leads and new coil.

What’s next? Any thought?

[clive]

Fuel system? I don't know what products are on the market nowadays, but the likes of Redex or similar carb cleaner run through the carb intake might clean the jets without having to do a strip down.

[Dave Woodward]

After all that, it was the timing that has too much advance. All fixed now.

[clive]

Glad to hear it's OK. I am surprised that it was the timing unless it has always been problematic.