4 Bolt Mc6

[steveohara]

Tom,

Or anyone else... I would be curious to know if anyone has ever investigated whether there is any difference in performance, output etc between the older coils with the sharp 90 degree corners vs the newer style that has the nice rounded shoulders??? When I handle the different versions it feels like the later model with the rounded shoulders weighs more and I wonder if the two coils have the same internal windings??
Steve O'Hara

[Scott Kneisel]

They don't have the same windings.
The newer coils have a secondary winding resistance of about 6200 ohms whereas the older ones have a winding of around 3500 ohms. Primary resistance is very low and about the same for both coils at about 0.5ohms but that is hard to measure without a proper resistance bridge which I don't have access to anymore since I retired. There could be minute differences which could make a difference in the output.

All this translates to a theory that the later coil should have a higher voltage output because of the greater ratio but in my experience the older coils seem to have a more robust spark although I have never measured the output. It may just be my perception.

Scott

[steveohara]

Scott,

I've only run a couple motors with the old style coil and they ran great. Both versions create an amazing spark just spinning a motor over by hand when they are set up right.
Would the later version perhaps be more effective with the spark plug under heavy pressure from compression?
Steve O'Hara

[Terry Bentley]

The 4 bolt block,if actually an original Mc 6 would be same as 1-62 saw block. Unless a 1-45 with X port added. A friend of mine was a Mac dealer back then and always acquiring replacement saw blocks that were not stamped. Unfortunately most of the saw blocks did not have all of the ports drilled. I guess I could say my 4 bolt Mc 6 is a very rare "factory mod" since it has only 2 oval exhaust ports and dual ball bearing crank.