One breather cap or two?

I picked up some SBF valve covers today that have a pre-drilled breather/cap hole on one side and none on the other. I am not running a PCV setup, so is a single breather cap (Edelbrock open breather cap) enough or should I drill the other side and add another one?

I found some articles with differing opinions, but the overall consensus seems to be that one is fine if it's not a racing or super high speed application.

Thoughts?

 

Breather on valve cover, PCV on the other running to a fitting under your carb. Your engine will be happy-

 

Your engine needs some kind of breather system. Put a breather with a built in PCV on the other VC and connect it to the carb base. If you don't it will always be oily around the poorly working breathers. You'll never keep the engine clean.

 

yes been said before.........mongo like candy........sorry, i ment motor like pvc...........

 

Next question....
If I decide to add a PCV, can I run it into one of the plugged ports on the intake (Holley intake for SBF) instead of drilling out the valve cover? I have a couple of different sized ports behind the carb that would hide the PCV perfectly if that would work.

 

Unless they go into the lifter valey and not an intake port then no.

There is a thread on here somewhere where somone did that on a SBC, untold amount of razzing from people telling him he drilled into the plenum or the runners (I trust he didn't, as he swore it ran great). So if you want to drill your own hole for it, yeah that should work, and there are PVC valves that thread in FWIW.

 

This might help. The PCV sytem is often misunderstood.

 

You can drill and tap a hole in the rear of the manifold so that it accesses the valley, screw in a PVC from a mid-60's Vette, and run that to the carb base. I did that on mine so as not to cut-up my Cal Custom valve covers. You could also use the existing valve cover hole for a PVC and install an oil filler tube in the front of the manifold with a breather type cap.

 

Thanks, good info, I sure have had a misunderstanding of the pcv system.

 

I have just fitted a screw in cap on one side and the PCV is the other.
Should I need a breather as well? [probably a dumb question!]

 

Yep. To work right the engine needs air to flow through the crankcase. It has to enter in one location, pass through the engine and exit at another location not near the first location carrying gases and moisture with it.

There are several ways of doing it but if you want to cool the whole house you can't do it with 2 open windows in the same back bedroom.

 

Update:
I found another valve cover with a filler tube/cap in it that matched the other side. I installed a PCV cap on one valve cover with a tube running to the base of the carb. On the other valve cover, I have a regular breather cap.

Now, this might be getting a little too particular, but is there a better way to position the breather side and pcv side? I put the breather cap on the side with the filler hole near the front of the valve cover and the PCV on the one with the filler hole at the back of the valve cover. I figured that would be a natural flow with air entering at the front and leaving out the back.....better crossflow.

 

I do it like that (breather forward and PCV valve aft) to make it easier for me to get to the oil filler (breather).

 

does the valve cover with the pcv valve in it have a sheet metal deflecter under it? other wise it might just suck oil into the motor and cause massive oil consumption. this happens alot on Cal Custom covers and other aftermarket covers that get drilled for the pcv valve and don't have the deflecter in them. oil can be squirting up from the push rod under the pcv valve and sucks it right in

 

It has an oil baffle...a pretty big one, too. They are stock aluminum Mustang valve covers probably from the early 90's. Not very "retro" but they actually look pretty decent painted low gloss engine black with some pinstriping on the big flat top surface. Besides the big oil baffles, they also have fairly long filler tubes. I cut them down slightly so I could install the breathers that I wanted, but they still provide lots of clearance away from any splashing oil.

My Mickey Thompson valve covers probably looked cooler, but they sucked a ton of oil into the breathers and deposited it all over the engine and firewall. There are only two little baffle posts on the M/T's so even if I added baffles, I don't think they would be big enough. The HO302 and high volume oil pump can sling some damn oil!