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Old 10-07-2019, 10:09 AM   #1
BUBBAS IGNITION
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Default Helmet and why not ????

I get a ton of questions each and every week asking about the newer electronics and other replacement distributors. Usually from someone with a chevrolet thought process. Its tough for a chevrolet small block guy to imbrace a flathead !! (I would be a good example guess as it took me a few years ).
Often the first thing to change would be the distributor. I just today finished a Model 68 Helmet with two bolt coil. This unit uses a dual set of contacts and the small cam . Once set up and adjusted i have ran it for over 30 minutes at 6000 rpm , the unit has 9 degrees of mechanical advance ( 18 engine) and has performed perfectly with a dwell of 36 degrees !!!
Cant imagine why you would ever have the need to change this unit. This one has a new 12 volt coil and good caps . A new set of wires and it should run forever ......
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Last edited by BUBBAS IGNITION; 10-07-2019 at 10:18 AM.
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Old 10-07-2019, 10:14 AM   #2
35fordtn
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Default Re: Helmet and why not ????

Jim the only thing better would be a 11a helmet in my opinion. I’d much rather have a 68 or 11a helmet over a crab! And as you well know many think the crab is the u it to have, but a 11a helmet performs the exact same! Nice post and excellent work! Thanks to your informative posts on here people seem to finally understand the workings of these units. Keep up the great work!
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Old 10-07-2019, 10:30 AM   #3
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Default Re: Helmet and why not ????

Quote:
Originally Posted by BUBBAS IGNITION View Post
I get a ton of questions each and every week asking about the newer electronics and other replacement distributors. Usually from someone with a chevrolet thought process. Its tough for a chevrolet small block guy to imbrace a flathead !! (I would be a good example guess as it took me a few years ).
Often the first thing to change would be the distributor. I just today finished a Model 68 Helmet with two bolt coil. This unit uses a dual set of contacts and the small cam . Once set up and adjusted i have ran it for over 30 minutes at 6000 rpm , the unit has 9 degrees of mechanical advance ( 18 engine) and has performed perfectly with a dwell of 36 degrees !!!
Cant imagine why you would ever have the need to change this unit. This one has a new 12 volt coil and good caps . A new set of wires and it should run forever ......
Jim, How much voltage can a helmet rotor handle, in case a guy runs higher cylinder pressure or larger plug gaps? It's been my understanding (could easily be wrong) that these rotors can short to the shaft if subjected to higher voltage,like a "hot" coil or a 12 v. coil can produce.
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Old 10-07-2019, 11:34 AM   #4
alanwoodieman
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Default Re: Helmet and why not ????

yes they will short to the shaft, but an easy fix, just two layers of shrink tape and your back in business
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Old 10-07-2019, 12:26 PM   #5
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Default Re: Helmet and why not ????

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Old 10-08-2019, 08:12 AM   #6
BUBBAS IGNITION
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Default Re: Helmet and why not ????

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Quote:
Originally Posted by 40 Deluxe View Post
Jim, How much voltage can a helmet rotor handle, in case a guy runs higher cylinder pressure or larger plug gaps? It's been my understanding (could easily be wrong) that these rotors can short to the shaft if subjected to higher voltage,like a "hot" coil or a 12 v. coil can produce.
Goodpoint as thats always a concern in these old ignition systems . I made a tester once from a old NAPA Echlin training manual showing how to test Flathead helmet rotors using a coil set up to check for shorts.
Every rotor i tested showed shorted !!!!! A rule of thumb is you cant STOP secondary voltage ( you can prove this theory with a scope) if the voltage is high enough it WILL GO TO GROUND , you may not know where but it will go to ground.
The only thing you can do is control it , it will always take the least path of resistance . So keep the shaft insulated with shring tube , use good connectors, and good plastics should be ok. Even though we feel as if the engine mods are drastic , most flatheads use very low compression ratios and overly rich air fuel ratios....
Stay tuned as i am gearing up for some live engine testing with a lab scope this winter......

As far as a hot coil is concerned a coil will only produce what the engine asks for . The compression ratio may ask for extra but the three carbs ( maybe rich) will ask for less and the trade off may be just normal spark is needed .....
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