I have a 1964 3.8 FHC E-type. My car is still a positive ground with a generator. This has not been a problem with a high torque gear reduction starter, high performance swirl blade radiator cooling fan and electronic fuel pump (no points). I have installed a Pertonix Flame-Thrower distributor and a Pertronix 40,000-Volt 3.0 OHM coil. This set-up is working great. The advertising states that this delivers twice the voltage to spark plugs to increase horsepower, fuel economy and spark plug life, and 2:1 improvement over points in current fall time for increased coil output.
My Service manual says the plugs should be replaced every 10,000 miles and cleaned and checked every 2,500 miles with a gap of .025. The manual mentions that the gap settings recommended have been found to give the best overall performance under all service conditions. They are based on extensive dynamometer testing and experience on the road, and are generally a compromise between the wide gaps necessary for best idling performance and the small gaps required for the best high speed performance.
I had always thought in general the larger the gap the hotter the spark that was generated.
I am interested in what others have found to potentially increase performance. Should I consider a certain type of plug wire? I have been reading about Denso iridium u-groove plugs in particular. It looks like the IW16 plug is recommended and come with a .035 gap.
Has anyone experimented with various gap settings?
Thank you, Don

Submitted by wcjssj@comcast.net on Fri, 06/19/2009 - 02:13

Hi Don

I have a pertronix unit and a high voltage Lucas coil. I have been using standard Jag plugs of various makes. All seem the same. I tried the 0.035' gap, but found poor performance at rpms over 4000. Im back to a 0.025" gap.
All gas stations used to have plug cleaners. Havnt seen one in 30 years. Change my plugs when I change the oil. Of course unleaded gas keeps the plugs much cleaner.

Have fun

Curt