PCV... to be or not to be

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shellbuyer

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PEI Canada
My Car
1973 Convertible Mustang
I have nice Ford racing valve covers on my 351 C. after my rebuild, here is my latest query. On the passenger side rear valve cover there is a plastic elbow that was on the original valve covers I took off, so I plumbed that to my breather. Now on the front drivers side, there is a nice Ford racing cap that has a hose attachment which I plumbed to carb where PCV hose is supposed to be. The only issue is with the Ford racing cap there is no provision for a PCV? Does this matter? or will it hurt anything not having a PCV? The old oil filler cap had one in it.

 
You should get your PCV to work. I used the same valve covers as you, I think, look in my garage in the 'modifications' tab and you will see what I am talking about. I hooked up the PCV to the passenger valve cover and just put a breather cap on the other side.

 
You should get your PCV to work. I used the same valve covers as you, I think, look in my garage in the 'modifications' tab and you will see what I am talking about. I hooked up the PCV to the passenger valve cover and just put a breather cap on the other side.
he will not need a breather cap on the other side if he has a hose plumbed to his breather. but there should be a PCV filter where that hose connects...on the inside

 
You should get your PCV to work. I used the same valve covers as you, I think, look in my garage in the 'modifications' tab and you will see what I am talking about. I hooked up the PCV to the passenger valve cover and just put a breather cap on the other side.
he will not need a breather cap on the other side if he has a hose plumbed to his breather. but there should be a PCV filter where that hose connects...on the inside
Right. I just used a breather cap, similar to 'guys72mach1' pictured rather than trying to run it to a breather inside the air cleaner. Partly for the cleaner look and also because my air cleaners didn't have a good place for a breather inside.

 
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OK - so which PCV should be used? The Fram FV111 (I believe) is no longer offered through my local parts stores (even though they spec'd that unit). Not to mention, the Fram unit doesn't have the 'elbow' on top... it comes out straight up.

I have an Edelbrock breather on the driver side, and a Mr. Gasket breather with a hose outlet - is there an 'inline' PCV that could be used (cut the hose and place inline)? I'd love to keep the Mr. Gasket cap on there and still have proper PCV control.

 
I used my original PCV on passenger side, plumbed to carb. and then plumbed oil breather cap to air cleaner base. I even made a linkage extension yesterday for my kick-down rod! I was on a roll. Now hopefully all is as it should be...

 
When I had my engine builder do the initial timing and tuning, we put a chrome oil breather in the rear passenger side valve cover and plumbed the PCV valve from NAPA to the rear of the carb. Car runs great.

 
If you cannot find a new PVC valve at a parts store, go to your local junkyard and find a used one. Throw it in a small bowl of laquer thinner for a few hours. After a few hours take it out and see if it rattles. If it does, take a can of brake clean and insert the hose in the top and bottom of it and finish flushing it out. PVC valves don't wear out, they just get plugged up with crud and sludge, but they can be renewed.

 
No PCV = oil leaks...need to run the PCV valve. You can get the Ford Racing PCV valve grommet from Summit for like $8.
I love this look...so nice and clean. Just to make sure I'm clear - this should work fine, correct? PCV valve on passenger side valve cover to carb and breather cap on driver side valve cover.

DSF7402 (14).JPG

Thanks,

John

 
Yes, you can put the PCV valve on either valve cover and the breather on the other. Stock mine had the PCV on the driver side and the breather was plumbed to the air cleaner and had a little filter on it.

Getting it to the air cleaner is actually 'a little better' than just a breather cap. But I don't have a prevision for a breather on my air clearners so I just have a breather cap like similar to what is pictured.

 
I picked up a second OE style twist cap and plumbed both to the back of the carb through 2 PCVs. The idea is to try and introduce less than atmospheric pressure into the crankcase for better oil control. I don't know if it works but it can't hurt.

 
I picked up a second OE style twist cap and plumbed both to the back of the carb through 2 PCVs. The idea is to try and introduce less than atmospheric pressure into the crankcase for better oil control. I don't know if it works but it can't hurt.
Careful with that mod-while it will reduce crank case pressure, it can result in excessive oil being sucked into your carb or intake.

 
"I picked up a second OE style twist cap and plumbed both to the back of the carb through 2 PCVs. The idea is to try and introduce less than atmospheric pressure into the crankcase for better oil control. I don't know if it works but it can't hurt."

that is not a good idea. your creating a massive negative pressure inside the engine block, oil consumption and other bad things can occur, more is not better.

the idea is you want to create a slight negative pressure inside the block thus you have a breather on one side and a PCV on the other creating a controlled vacuum leak, that only creates negative pressure when vaccum is very high, idle, cruise, and off when vacuum is low, acceleration, load on engine.

the breather can be either part of the air base cleaner or a breather cap. breather caps suck because they can blow oil on the valve covers.

the air cleaner breather is better because the hose rises up to the base and any heavy oils never make it up to the filter just the very light oil soaks the filter in the base, the base filter eventually gets gums up from the dirt going through the main air filter and the oil in the breather gets gummed with dirt so you want to replace the breather filter in the air cleaner base when you clean the main air filter.

the cap breathers just spray crap all over when you accelerate and vacuum drops

but you need to have open atmosphere on one side and a controlled vacuum leak on the other which causes a slight negative pressure in the block because of all the internal restrictions inside the engine.

2 pcvs on both sides is making negative pressure all the time with no release, you could suck in a gasket or oil or blow out the fuel pump diaphragm, there is no equalization inside the block when you let off throttle or acclerate just constant negative pressure that is looking for a way to get to normal atmosphere somehow.

 
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