Slick 60's

Hi guys,

Think I know the answer here but just double checking. My engine vac at idle is around 13.5 inches and idle is rough. When I plug off the hose leading to the large side of the vac advance module, the vac at idle goes up to 15.5 (better).

Sounds like the large diaphram is leaking to me. You guys agree ?

Also, any idea what vac level I should be targeting i.e. 17 in's ?

Thanks

Sounds like a bad one to me. You could test it with a hand held vacuum pump...I wouldn't recommend sucking on the line to test it, you may just end up with a mouth full of dirt.