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Distributor Mystery

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Tim_Creger

Tim_Creger

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Dear Forum,

I've posted a few questions about my electronic ignition over the summer,and now have a whole new oddity to ask about. I bought a new Pertronix EI distributor to replace the original that quit working in my MGB ('72 car with a newer B engine). The previous thread was asking basic questions about static timing the engine, which I've done a dozen times with no success. Today I decided to see how the old dizzy and the new one matched up. With the #1 cylinder on TDC I installed the original dizzy and see that the rotor is at the 8 o'clock position. Everything I've read says it should be at the 1 o'clock position. I then installed the Pertronix dizzy and observed the rotor at the 2 o'clock postion, exactly 180 degrees opposite the original.

I pulled both units out, laid them on the bench side by side, matched up the offset drive dogs so that they were in the same position, and see that the rotors are 180 degrees opposite in position. I've never heard of this situation, and yes, I made sure that the drive dogs were correctly seated when I installed them, and that is why I did the bench comparison to make sure I was seeing what I was seeing.

Can anyone refer me to a distributor expert - I've seen some posts referencing someone, but can't find the contact info for that person.

Any help would be gratefully appreciated. I also posted a few photos for anyone to look at and tell me if I'm missing something obvious.
 

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Tim, if the offset dog is 180° on the P-unit from the old diz, just juggle the wires at the cap to work the same way. The electrons don't care, <span style="font-style: italic">you'll</span> know what's what and the rest of us won't tell. :wink:
 
Dr. E.

Yes, I thought of doing that: "Juggling" wires by moving them all two spots clockwise (or counter-clockwise, it matters not in this case). However, given the old dizzy is 180 degrees off of what I've read it should be, what are the chances the timing chain has slipped? The engine was rebuilt about 10,000 miles ago by Ivor Searl, an engine rebuilder in England. I have a hard time believing the timing moved that much, but stranger things have happened, I suppose.

The reason I asked for Jeff's contact info is that I am thinking about sending him the old unit to rebuild, and then use it to work on the timing, since it can be static timed. I don't think I want to experiment with the P unit, as they are sensitive to toasting the modules when ignition is on and the engine isn't running.

Tim
 
When one of the distributors (don't know which) was assembled the upper part (above the flyweights) was installed 180 out. It DOESN'T matter to the engine which way it was assembled so long as the fire goes to the right plug at the right time.
The timing has not slipped- the new (probably) distributor was just assembled backwards- no problem!
BillM
 
Tim said:
The reason I asked for Jeff's contact info is that I am thinking about sending him the old unit to rebuild, and then use it to work on the timing, since it can be static timed. <span style="font-style: italic">I don't think I want to experiment with the P unit, as they are sensitive to toasting the modules when ignition is on and the engine isn't running.</span>
Click to expand...

Good thinkin' Sir! We've seen a number of toasted boxes for just that reason. There's a: "Those who switched back to points from petronixx.." thread over in the Triumph forum, interesting from both -points- of view. :wink:
 
Well, in follow-up to my last post, I have the following to report. I sent my old points distributor to Jeff at Advanced Distributors. He finished rebuilding it today, and when I called to check on it, he confirmed what I had suspected: the last rebuild of the dizzy was done such that the rotor was 180 degrees off of what it should have been had it followed standard manufacture design. If you look at the photo I posted earlier, you'll note the rotor pointing at the 7 o'clock position. This is what I found when comparing it to a new Pertronix unit that had the rotor pointing to the 1 o'clock position. This is with the engine static timed to the number 1 piston at TDC, and both valves of the number one piston fully closed (compression stroke). At that timing setting, the #1 plug should be firing, and all manuals I've ever read said the rotor should be at the 1 o'clock position.

Well, I didn't spot this upon removing the old dizzy to replace it with the new Pertronix, so it's no wonder why I couldn't get the new unit to run the car.

Anyway, I will have the rebuilt points dizzy installed soon and with any luck will have no problem getting the car started and running again.

Best to all,

Tim
 
Installed the rebuilt distributor, made sure to get everything set right this time, car started right up, ran a few minutes and died. See other thread "Not the distributor, but what?". It was the fuel pump, probably all along. :-(

Thank you to the board for helping diagnose the problem, it's good to have others to bounce ideas off of.

Tim
 
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