Third hole in valve cover

[blaylock6502]

As If u couldn't tell by now my 74 cj5 was kinda pieced together when I got it. I got a used valve cover in an attempt to fix an oil leak. I was getting ready to put it on and I was curious as to what goes in the third hole on the valve cover on a 258. I have the pcv and oil filler cap ( which is another deal All thogether). I was looking at pictures to see which hole was supposed to be the pcv because I have a breather and it is interfering with the oil fill cap removal. It doesn't look to me that it would make a difference which hole the pcv was in as the baffling looks the same and the holes are the same size?? But I looked at some pics of old used engines on craigist and it looks like there is a vacuum hose running to both holes? Also should the pcv have full manifold vacuum?

 

[PoliceMonkey161]

One hole goes to you air cleaner as an intake (or you can get a push-on breather element), the other has the PCV valve that is connected to your vaccum soruce.

 

[blaylock6502]

Awesome! Any idea if that's ported or manifold vacuum ( not that I'm exactly sure what ported means)

 

[PoliceMonkey161]

It would be full, normally at the base of the carb, below the butterfly valves/venturi's (throttle plate?). Ported means the vaccum side before throttle plate, so it is protionate to throttle increase (i.e. vacuum advance hose).

 

[69jeepcj]

To try and shed more light on what policemonkey said. Ported vacunm is above the throttle plate on your carb and has no vac or VERY little at idle, once you hit the gas pedel and crack open the throttle plates vac starts to build untill a certain rpm (probably around 3000) then drops off. manifold vac is below the throttle plates and gets full vac at idle up untill a certain rpm, (probably around 3000) The dif is at idle. manifold vac gives better idle, better gas milage, lower engine temps, better throttle response. ported was a crude emissions attempt starting around 1970-71. All engines after that came from the factory with ported. If you switch to manifold vac at your vac advance can on the dist, your rpm will raise at idle so you will have to lower your idle screw to bring your rpm back down. your timing will go up at idle as well, Say your initial timing at idle is 8* with ported vac, When you plug the vac advance line into manifold vac your advance now has full vac and will raise the timing at idle about 10* so your new initial timing at idle will be 18*. sorry I got carried away, I forgot you are just wanting to run the pcv, I would run the pcv on manifold vac.