Distributor SHOCK!

Ouch! Will someone remind me what causes an HEI to give you a good shock while setting timing? All the ignition wires are firing fine.  

There are lots of good reasons to get zapped. #1 40,000 volts minimum at idle. Everything looks good with no missed for the engine right. But most of these HEIs are running on the ragged edge of a miss. The resistant of the cap and area around the towers is higher than the plug and wires so everything runs fine. Remember the part about the path of least rsistance. So now insert your nice sweaty, greasey hand, which is low resistance path and ZAP you get to make a trip to the ER for stitchs in the back of your head that you just hit on that nice sharp edge for hood.  

Some dielectric grease under the boots that go to the distributor cap helps a lot.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Thanks PM8,
I always use dielectric grease on both ends, so I'm covered there. I just need to find which wire is bad. At least those 18,000 volts don't sting as hard in a dry garage with clean hands and a glove!  

Yep, No problem.  
professional hi-performance engine builder

Horsepower sells engines and torque wins races

Check the resistance of each wire and you should see one very different. If not, check the resistance on your spark plugs. They have resistance built into them to control burn temperature and build up resistance over time, or can be missed by quality control when made.  

when one of the wire terminal at the spark plug ends gets pulled off inside the spark plug boot..  it will increase the voltage needed to arc over and cause high voltage leaks until the rotor burns through...

i have also found missing ground straps under the HEI in cap coils and broken wiring harness up from the housing that removes the ability for the voltage in the frame of the coil to escape to ground ...   when this happens..  the coil will sometimes make little noises ... like a 12 gauge shotgun going off under the hood...   yes its that loud..

the spark has to complete a circuit...

out the coil high tension terminal...  through the button.. through the rotor.. jump the gap to the closest cap terminal. up to the spark plug wire..  down to the spark plug.. jump a gap there..      into the head.. into the block... into the dist hold down clamp,  up the distributer housing..    to the HEI capacitor hold down screw.. that if you notice also connects to the 3 wire harness to the cap...   to the little folded metal ground strap under the coil... through the coil laminations,  to the black wire that leads into the coil body..  


got a digital volt and ohm meter?????

set the meter to 200K OHMS...   200,000 ohms...    measure the wires...   if good... the direct reading on the volt meter should be less than the overall lengths of the wires... IN INCHES...

a 24 inch wire...  if good should be less than 24 on the display..    

a 12 inch wire should be less than 12 on the display...

usually it will be a half the length...

one thousand ohms per inch MAX...


i hope this explains it

when i first started working on cars for a living... a lady who owned the store down the block brought her V6 buick in..  it was misfiring..   i checked the timing.. it seemed to be way off...    i noticed that she had folded cardboard triangle tubes to run the spark plug wires through..  when i grabbed the hei cap like i did every day.. ZAPP...  the ends of the wires were pulled off and just shoved in...  this open circuit had to be jumped by the spark.. but it took a lot more voltage peak to flash over the gap..  the wire insulation was not designed for that kind of high voltage.. so i got zapped.. learned a lesson...  i hope i have shared a lesson...  

Yes you have, and it's right on the money. I've been experimenting with different size springs in the distributor this week, and when I had the cap pulled off to the side I didn't notice that #2 spark plug wire had gotten hung under the valve cover.
It must have loosened the connection. I checked it visually and the spark plug end was fine - but it must have pulled it loose at the other end which is harder to detect inside the elbow boot. I checked the resistence per Flynryan's advice and that revealed the shocking truth! I dislike being the ground for an electrical circuit. Thanks to all once again - no more head clank on the edge of the hood for sister Brazil.  

One thing I learned was that if the dist isn't grounded good, it will knock the crap out of you.