Rust was terrible in this distributor, MSD #8546, am replacing the reluctor wheel, pick-up, top bearing and seal. For someone that has done this, what did you have to do to get the reluctor wheel and locking pin installed on the head? File the wheel groove, freeze the head and heat the wheel, all of the above? I haven't messed it up , yet.
MSD distributor rust
- Thread starter Bird 426
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ckessel
Well-Known Member
Where was the rust located? HEI distributors, GM starting in 75, had an issue with rust freezing up the mechanical advance mechanisms. The cause was from faulty, high resistance plug wires. Too much resistance made the spark generated look for the least possible path. It would back track through the rotor, you could see a big burn mark circle around the center contact. It would blow through the rotor to the advance unit. Many times it would be severe enough to freeze up the mechanism. This would require you to take the distributor out, disassemble the unit entirely, remove the rust, lube up the mechanism and put it back together. When I worked at the stores, many sets of ignition components were sold to remedy after the problem was found. As far as putting yours back together, maybe someone else will chime in on that.
I think the thin core of the pick up coil triggers on the leading edge of the thick reluctor teeth... And I've watched enough wave forms to know I'm right... Do I prefer a thin tooth like Mopar used? Yeah... Do I think the fat tooth causes a problem? Nope...
Geoff 2
Well-Known Member
Well you need to watch even more wave forms because, nope, it triggers on the trailing edge, just as the sine wave passes the zero point as it goes negative.
The accuracy of when the trigger point occurs is determined by the air gap & accuracy of the reluctor machining. MSD specified reluctor gaps of 025 -050".
How accurate do you think the cyl to cyl variation is going to be with a 025" gap versus the 007-008" gap of Chrys & HEI??????????
Caption reads [ below]: Plug fires when trailing edge of reluctor aligns with with trailing edge of pick up.
The accuracy of when the trigger point occurs is determined by the air gap & accuracy of the reluctor machining. MSD specified reluctor gaps of 025 -050".
How accurate do you think the cyl to cyl variation is going to be with a 025" gap versus the 007-008" gap of Chrys & HEI??????????
Caption reads [ below]: Plug fires when trailing edge of reluctor aligns with with trailing edge of pick up.
Leading edge, trailing edge, it's an edge & it repeats consistently...... They are pretty stable...
The reluctor, pickup and top bearing were rust, top bearing was well on its way to being gone. Anything that was bare steel, except the black oxide shaft and weights. My question was the trick to install the reluctor wheel and pin back onto the head.
Will look for answers elsewhere.
Thank you.
Will look for answers elsewhere.
Thank you.
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Yes.....accurate repeatability.....the shape of the generated waveform, is the key factor.... be it positive or negative going, is usually rectified to produce a trigger pulse of a minimum amplitude that, is in turn, fed to the main switching transistor circuit to turn it off, causing the coil to generate the spark. Some manufacturers use this pulse directly, the MOPAR ECU and a programmable dwell circuit or some other manufacturers use this pulse to trigger an SCR, which discharges, a large series capacitor to the coil, as in a Capacitor Discharge system. Positive or negative going trigger pulse?? Depends on the rest of the circuitry and the manufacturer.......to prove conclusively, you need to see schematic of the device......just my opinion...
BOB RENTON
Just a dab of grease to hold the roll pin in the groove, slide the reluctor down till it engages the roll pin in the matching slot, then tap the reluctor home with a suitably sized deep socket & a small hammer....
Yeah, didn't use grease, the wheel just pushed the pin up the slot. I will try the freeze/heat thing tomorrow and see if I have better luck. Going to file the starting point just a touch to get it guided in. We'll see.
Well, this one isn't going as easy as grease it and knock it home. I have filed and messed around with it, finally lost the roll pin. Not a fan at this moment of MSD distributors, but it came with the car. None of the rusted parts, in my opinion, should ever have been rusty in the first place. Will call Holley in the morning and be open minded to their wisdom, and of course, more parts.
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