Test for Cracked Distrib housing and Rotor??

[Bill Goddard]

I have been reading about distributor problems and checking for cracks in distrib hsg's and rotors but no mention of how to do the check. I don't think a simple continuity check between terminals on hsg would detect a potential high voltage jump in operation. Can you use a paint wiped over the plastic in hopes of filling a crack similar to Zyglow? Are some cracks so fine that they can't be seen with naked eye but will still cause a breakdown?