Oil Breather Cap Question

[427 Street]

I just changed my valve covers on my '64 427FE from chrome baldies to 427 Cobra finned-aluminum covers. I was not told when I bought the new covers that the current oil breather cap would not work....I was also not told that I needed two breather caps. I found some temporary twist on oil caps at NAPA today.

Question: Do I need breather caps? The back of my intake vents to the carb so I am assuming I do not need any additional venting, but I am not sure. You can see the hose from the back of the intake going into the Holley.

I think these are the correct twist-on caps: Mustangs Unlimited - The Premier Source for Mustang, Shelby and Cougar Parts and Accessories

Pics of the engine...before and after. I also changed from the 8" Stelling-Helling to the correct 14" air cleaner which would have been found on the street cars. Next? Change the red wires...

[Gaz64]

Fresh filtered air needs to be plumbed to one rocker cover, since you have a pcv valve at the top of the lifter valley.

The engine also needs to "breath" crankcase PRESSURE via a filter on the rocker cover, or a hose going to the base of the aircleaner.

[vector1]

i wouldn't run it without some kind of vent, whether you have a pcv valve or not. you will start weeping oil or blowing gaskets if the crankcase pressure builds too much. nice looking engine bay.

[427 Street]

Thanks for the replies...do I need two breather caps, or can I get away with just one?

I am still not sure what the "breather" is on the back of the intake and going into the carb. It used to be a stack with a breather on top. The previous owner said it was misting too much oil around, so he had Gessford Eng. build the base and he ran the hose to the carb. I thought that was the equivalent of the rocker breathing into the air cleaner....guess not.

[mickmate]

Those caps you found look correct and are breather caps. With that PCV set up you have and the two breather caps that should be fine and look good.

[Wbulk]

X2 on on the first two comments. The concept is there needs to be filtered air going into the valve cover which becomes the source for the PCV valve where the air is sucked into the back of the carb. You have cut off that air supply and you have no crankcase ventilation. Some of the original FE engines had the screw in breather that had a hose that went to the underside of the air cleaner. To add oil you just do a 1/4 twist like the cap you have, and set it aside with the hose attached. I have an old one laying around somewhere. I will see if I can find it and take a picture.

Added:
I looked but couldn't find it. Another option is there is a grommit that goes in the cap hole you have so you can use a push in breather. It just covers the ears of the screw in cap. Not ideal but it works.

[Tom Cimino]

Those caps you found look correct and are breather caps. With that PCV set up you have and the two breather caps that should be fine and look good.
Like

Mick,

Are you looking at the right photo? The way I read it, the second photo is how the car is set up now. The oil cap on the driver's side valve cover doesn't look like a breather to me. If the other side is the same, air can't be drawn into the crankcase and pressure will build and oil will start seeping out and blowing down the intake from the pcv valve.

[vector1]

you can use one breather if it flows freely. one reason i don't like breathers, even with a pcv, is they tend to put oil mist into the engine compartment, so if you do experience some it is normal.

[mickmate]

Mustangs Unlimited - The Premier Source for Mustang, Shelby and Cougar Parts and Accessories
He's talking about putting these on.

[Wbulk]

Mickmate, better than the one I was thinking of and should work fine.

I found the old one. If I remember right some of the big FEs had two ventilation systems. The crankcase can create a lot of pressure. I can't remember how the other one worked.

[mickmate]

Originals were set up a couple of different ways. Most used an intake breather cap/fill tube at the front of the manifold. Some had a gooseneck style breather at the back of the manifold. Street cars often had the style cap you show on one side with the other side valve cover plumbed to carb. Towards the end of production I believe they were using the PCV plates on the back of the manifold as OP has done.

[Mongoose930]

Here is a picture of the breather cap / fill tube on the front of my intake manifold.

[FWB]

i bought these twist on breather type at Napa for my covers. i didn't buy them for any particular application, i just had them bring out a bunch they had and i picked what i wanted.



note the cap you linked EC 564 is a motorcraft part number. they are available at the dealer or any motorcraft reseller, i think Napa sells motorcraft also, may have to order them....

[427 Street]

Originally Posted by FWB

i bought these twist on breather type at Napa for my covers. i didn't buy them for any particular application, i just had them bring out a bunch they had and i picked what i wanted.



note the cap you linked EC 564 is a motorcraft part number. they are available at the dealer or any motorcraft reseller, i think Napa sells motorcraft also, may have to order them....

Perfect...I will call NAPA now, thanks. That is the part number that I wrote down as well.

Where did you get your wire trees?

Thanks again.

[FWB]

the wire separators are moroso, i drilled holes in them, riveted them to the tangs

[Barry_R]

You need at least one breather cap to go along with the PCV. You will have a degree of blowby no matter how good the engine is. It needs someplace to go - otherwise it will pressurize the crankcase and cause leaks - the pressure WILL find a way out if you do not provide one.

[427 Street]

I went to NAPA yesterday because I had ordered tow twist-on breather caps. I am definitely disappointed in the quality. The gasket is very cheap in appearance, and the chrome finish is poor.

I prefer all chrome like the Motorcraft EC-564 OEM caps, but I did not want the red MC decal in the center. I searched almost everywhere on the web. Any suggestions for a plain, chrome, high-quality twist-on cap?

[FWB]

good quality...i'm still looking...since 2006.....I was just happy to have found one to fit. i made new gaskets from neoprene for mine.
when the breather gets oil soaked, i just throw it out and get another one.
just about everything at Napa is now china....even dorman products.

[427 Street]

Okay, that makes sense. I thought it was just me Neoprene...good idea. NAPA said it was a Stant cap, so I assumed it would be nice...oh well.

This is nice, but at that price, I think it should be reserved for a show car and not for a driver which will be tossed as you said:

http://www.american-mustang.com/inde...roducts_id=344

I might just stick with the NAPA ones, even though they are tight/tough to get on and off. Or, I might get those Motorcraft (Scott Drake replicas) EC-564 even though I do not like the red decal.

[FWB]

the EC-564, is it just a sticker? remove it....a little Goo-gone
the Napa ones are going to oxidize on you. just be forewarned.....