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Old 03-14-2012, 12:21 AM   #1
1970CustomCamper
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Question MSD coil bad? Make my own plug boots?

I think my MSD StreetFire distributor with built in coil is burnt. Only had for 8 months. Contacts were burnt inside cap. Had power to coil, but no spark at plugs. Was warrantied and putting in new one now. No electrical ignition box, just standard oe ignition.

1. 4 spark plug boots closest to down pipes on rams horn exhaust manifolds were all cracked and melted. Did this burn out coil? From plugs arching?
2. MSD 8mm wires were expensive! Do I need to replace wires, or can I just replace 4 boots. They are straight boots (silicon).
3. Can I make my own boots out of 3/8" fuel hose? Or will that melt because not silicon?
4. I bought sleeves that go over boots to prevent this in future. Anyone have any experience with these? Made by DEI...

1970 3/4 ton GMC long bed, 350 with th350. Tow 2 ton utility trailer daily.
Thanks for your help,
Danny
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1970 GMC Custom Camper 3/4 ton, 350 automatic, th350 tranny, PS, 4 wheel drums, 8 lug steelies, Dana 60 rear end, Spanish Cedar & stainless wood bed, new interior, California truck w/ no rust (maybe just a little). daily driver, work truck & tow vehicle that wants to be a show truck someday...
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Old 03-15-2012, 09:42 AM   #2
Lee H
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Re: MSD coil bad? Make my own plug boots?

I'll give this a shot.

1) No and no. I'd guess you aren't running stock GM spark plug shields. If you don't have them you should.
2) The boots are replaceable.
3) NO!
4) Yes these will help, I use them with headers.
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1972 C10 SWB, Air, PS, PB, 350/350THM. Second owner.

1965 Corvette roadster, 44K miles, 327/365 SHP, 4 speed, side exhaust, knockoffs, teak, second owner (bought in 1970), Have ALL numbers matching components.

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Old 03-15-2012, 01:09 PM   #3
HEI451
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Re: MSD coil bad? Make my own plug boots?

What is the resistance of the carbon post between the rotor and coil??

Was it installed correctly? Sequence is, cap, brush with spring pointed upwards in cap, insulator, coil. IF the carbon post was incorrectly installed, above the insulator, and/oir it has too much resistance, the possibility of the coil failing is great.

The ONLY way to test the coil is to remove it from the cap, then, take it to a good auto parts store, one that has an off vehicle testing machine, connect it up, and let it run to get it to full operating temperature. Resistance tests of coils and HEI modules are absolutely useless any more, run testing is the ONLY way to get coil health revealed.

The EPOXY filled coil in cap, large HEI COILS are very prone to failure because of heat. They do what is called "layer shorting", the heat destruction of insulating layers between primary and secondary windings. When thins happens, coil temps go nuclear, much higher than normal for an epoxy coil, and that heat is resistance, which is work the parts have to do. The "work" increases well past the level the system can stand, HEI modules being the first part to fail from the over-work. This is because EPOXY does not transfer heat away from coil internal windings, it holds the heat inside the coil.

The ONLY way to fix the coil in cap heat issues is to use a round, remote mounted OIL FILLED coil, out of the large HEI cap, NOT a round/square epoxy filled coil.

And, I consider the MSD products, for the most part, excellent, top notch, save for their coils, all of them (Chinese made, very low quality, and VERY layer short prone), and the "Ready to Quit" and "Street Mis-Fire" systems. Everything else they have is the best you can get.
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