Valve Covers

[minifridge1138]

I just bought a pair of pro-form valve covers. They are black and say Chevrolet in red letters. I was comparing them to the old covers, and noticed that the new ones do not have a hole for the PCV valve. I have also noticed a lot of crate motors in magazines with the same valve covers and they also don't have a PCV valve, but they do have Breather caps. Can I use a breather cap instead of a PCV valve?

I appreciate the help

 

[minifridge1138]

checkup

Hello? Anyone have any ideas?

 

[JohnZ]

I just bought a pair of pro-form valve covers. They are black and say Chevrolet in red letters. I was comparing them to the old covers, and noticed that the new ones do not have a hole for the PCV valve. I have also noticed a lot of crate motors in magazines with the same valve covers and they also don't have a PCV valve, but they do have Breather caps. Can I use a breather cap instead of a PCV valve?

Only if you don't mind having hot oil mist all over your engine compartment - that's OK for race car engines, but sucks on a street car.

Just drill 1.22" diameter holes in the valve covers (in the same location as in the stock covers so they don't interfere with a rocker arm) and use the original PCV grommet and valve on one side, and the valve cover-to-air cleaner intake grommet and elbow/hose on the other side.

 

[minifridge1138]

Thank you

I hadn't thought about hot oil mist. yeah, good call.
Thanks for the feedback.

 

[Tom Bryant]

Your original valve covers and many after market ones have an oil baffle under the PCV hole to separate the oil mist from the vapors that are drawn out through the PCV valve. When adding a hole to a valve cover it is a good idea to add a baffle if you can. Some valve covers aren't thick enough to drill and tap blind holes that won't show on the outside and you don't want screw heads showing either. The perfect cure for this is this PCV grommet from Moroso that has a built in baffle. It's available for $5.50 from Summit. I was going to use it on some covers I was considering but I bought a pair of Billit Specialties ones that had the bolt bosses for the baffles cast into the under side and included GM style baffles in the package.

Here's the link to the Summit page.

Moroso PCV grommet.

Tom

 

[minifridge1138]

Baffled

OK, my original valve covers were the short ones. The new ones are tall. And both the left and right have oil baffles. Does that mean that i can just put an oil breather in, and not have any problems?

Yes I am fairly new to a lot of this, but the only way to learn is to ask.
Thanks for all the help.

 

[JohnZ]

OK, my original valve covers were the short ones. The new ones are tall. And both the left and right have oil baffles. Does that mean that i can just put an oil breather in, and not have any problems?

Yes I am fairly new to a lot of this, but the only way to learn is to ask.
Thanks for all the help.

Tall or short doesn't matter, nor do baffles - if you use breathers instead of the correct PCV setup, it's going to blow hot oil mist out of the breathers, as all they provide is pressure relief, not ventilation.

Crankcase ventilation is a closed system - draws in outside air from the air cleaner on the passenger side, draws it through the crankcase, exhausts it through the PCV valve on the driver's side, through the hose to the carb base, where the vapors are drawn into the intake and burned with the incoming air/fuel charge.

 

[minifridge1138]

problem solved

yeah, i only mentioned the tall vs short to say that i had plenty of room for a baffle without hitting the rocker arms.

The only reason i was thinking of using breathers instead of PCV was to reduce the amount of vacuum hoses. I know i've still got vaccum leaks someplace and the less hose, the less potential leaking.

I've seen some breathers that get clean air from the air filter, and some that are just a filter that plugs into the hole in the valve cover. Any particular reason to go either way?

 

[JohnZ]

yeah, i only mentioned the tall vs short to say that i had plenty of room for a baffle without hitting the rocker arms.

The only reason i was thinking of using breathers instead of PCV was to reduce the amount of vacuum hoses. I know i've still got vaccum leaks someplace and the less hose, the less potential leaking.

I've seen some breathers that get clean air from the air filter, and some that are just a filter that plugs into the hole in the valve cover. Any particular reason to go either way?

Any breather that just plugs into the hole in the valve cover is going to blow hot oil mist all over the place from crankcase pressure. There are no additional vacuum hoses involved - the stock setup had an elbow in the passenger side cover with a large hose to another elbow in the air cleaner, and a PCV valve in the driver's side cover with a 3/8" hose to the port in the carb base - that makes a closed system that works and doesn't blow oil mist. Just duplicate it with your new covers.