got a wierd problem.

when i did my engine wap into my 72 duster, i installed a GM HEI distributor that was fitted for mopar. its just a simple summit brand dist. anyways. ive had it in the car for abt a year with no problems. but ive recently spotted an oil leak at the back of the engine. i resealed the oil pressure fitting, replaced the o-ring around the dist but that didnt help. i also replaced my pcv valve. i took the cap off the dist and found oil inside the dist. ive asked all my buddys and local shop owners and non of them have heard of this. apparently oil is coming up through the shaft. there are no other oil leaks on the whole engine. any ideas?

thanks