flathead ignition


5237 FORD STreet speedway IN 46224 us


First comment is based on “need” , we do so many things to hot rods based on cool and very seldom need. Ignition is one of those areas , do we need a MSD 6A and a blaster coil with larger plug wires on a 9 to 1 compresssion flathead turning 4000 to 5000 rpm max ? Of course the answer is NO.
However the cool factor is there for sure.

The flathead engine having good compression and proper air fuel ratio with a proper rear axle .

( another forgotten area) would use approx 4000 to 5000 volts to fire the air fuel mixture at idle and maybe 8000 volts under load. A typical coil would supply 20,000 to 25,000 volts under snap throttle load.
So the ignition system would have 8,000 volts required and 12,000 to 17,000 volts reserve voltage available. In the olden days that would buy you 20,000 miles of driving ..before the old “tune up”.. A tune up would restore the parts back to the 5,000 volt level and we could now drive another 20,000 miles. Tighten the carb ( air leak is lean requires more voltage), replace or adjust the contact spacing (dwell is spark energy based on coil build up) and adjust the air fuel mixture with timing adjustment. (the way it used to be)
Now fast forward to the mid to late 70’s, federal emission laws were put in place that the oem had to certify the emissions for 50,000 miles etc. This couldnt be done with the old tune up levels required so something new had to happen.
The fix was to make the ignition electronic with no adjustable parts to speak of making the vehicle capable of running 50,000 without any actual ignition service needed. Fuel was now better and the plug manufactures used a new for the day extended tip plugs to also offer some heat change automatic adjustment based on driving style etc.. In reality we now only needed only 3,500 volts ( better eveything) and the reserve voltage in the coils was raised to 40,000 -50,000 volts to extend the driving emission certifications…. By comparison today in 2015 the igntion is certified emission wise for 100,000 miles and many last even longer !

Ok lets try to answer the question: Electronic Crab or points ???
The Ford crab is a very good ignition system using a dual set of contacts and provides a long drive cycle once cleaned and adjusted. However many want the electronics added to the system based on a fear ( not need) of the contacts and condensors failing from time to time. We build a few hundred of these each year and the ratio is 1 out of 5 are electronic.
Understand there is a large difference between “electronic” and ” high energy” with the electronic requiring the contacts as a switch taking away one of the maintance items and the high energy actually raising the output voltage of the system.
With the crab we dont wish to raise the voltage levels as the cap to rotor to case clearance wont allow high voltage as the spark will jump to the case. If high energy is needed we would supply a aftermarket unit with different cap, rotor style and distributor case etc.