Engine New 5.0 Build - PCV, Breather, Both, or ????

ameration · Mar 8, 2023

Just finished rebuilding the 5.0 for my son’s 1995 GT (Trick Flow Cam, Keith Black -3.00cc Pistons, Blueprint Cylinder Heads, Ford Performance R302H Lifters, Roller Rockers, etc…). The new, taller valve covers both have the breather holes in them. The lower intake (GT40) also has the PCV hole in the rear (and we have the OEM PCV).

My Question is, do we run the PCV to a catch can (using the lower intake position in the middle of the motor), run only a single breather in one valve cover (and which side), run the PCV and a breather in both valve covers, PCV and a breather in only one valve cover (and plug the other), only run breathers and cap off the PCV, or what …. and why?

Thanks so much for the help with this.

General karthief · Mar 8, 2023

Ok, the engine in these cars have a 'closed PCV system' meaning no breathers, all the out side air entering the engine is metered through the maf, one valve cover should have a hose connected to the throttle body and the PCV is connected to the intake at the back and the intake plenum.
Reason is no combustion gases escape the engine, the crankcase air is cycled back through the combustion process and out the tail pipe.
Has no effect on power.

AeroCoupe · Mar 8, 2023

The General is spot on however one of the holes on the valve covers will need to be used for an oil fill. So you will need to find a way to plug the hole that is not used and add a filler neck to the other one. This is what I used for the oil filler neck and cap:

https://www.trickflow.com/parts/tfs-51400806

https://www.trickflow.com/parts/tfs-51400807

I also had an aluminum 1/4" NPT fitting welded into the filler neck for a barbed fitting to be installed. From the factory there was a vacuum hose conencted from the Throttle body to the oil filler neck. Here is what is looks like finished:

ameration · Mar 8, 2023

General karthief said:
Ok, the engine in these cars have a 'closed PCV system' meaning no breathers, all the out side air entering the engine is metered through the maf, one valve cover should have a hose connected to the throttle body and the PCV is connected to the intake at the back and the intake plenum.
Reason is no combustion gases escape the engine, the crankcase air is cycled back through the combustion process and out the tail pipe.
Has no effect on power.

Correct - however I’m trying to avoid all of that oil getting back into my intake (old intake was very oily inside but the worn rings allowed lots of blow-by).

Are you suggesting to cap the valve covers and run the PCV only or set it back up like stock (he stock pass. valve cover has a hose that went into the intake tube before the TB in addition to the PCV vac line.)

Noobz347 · Mar 8, 2023

I was going to pop in just to scream, "You can't have both! "

But I see you're in good hands

General karthief · Mar 8, 2023

Look at a pic of the stock PCV system on a fox 5.0, as a matter of fact any EFI 5.0 from 86 till (95 for fox model) till mid 90's for any EFI 5.0 push rod engine and the PCV system is pretty much the same.
Does the engine have some blow-by?

mikestang63 · Mar 8, 2023

Run the PCV unless running high boost. That is what Ford engineered.

ameration · Mar 8, 2023

General karthief said:
Look at a pic of the stock PCV system on a fox 5.0, as a matter of fact any EFI 5.0 from 86 till (95 for fox model) till mid 90's for any EFI 5.0 push rod engine and the PCV system is pretty much the same.
Does the engine have some blow-by?

Brand new build so shouldn’t have any blow-by.
The motor before it was rebuild had horrible blow-by.

General karthief · Mar 8, 2023

Did you clean the inside of the upper intake?

ameration · Mar 8, 2023

General karthief said:
Did you clean the inside of the upper intake?

Yes

Mustang5L5 · Mar 9, 2023

I run the stock style PCV but added an oil separator inline with the main PCV hose. .

Engine New 5.0 Build - PCV, Breather, Both, or ????

ameration

Attachments

General karthief

wonder how much it would cost to ship you a pair

AeroCoupe

lube between the nut and the face. I know my lubes

ameration

Noobz347

Stangnet Facilities Maint Tech... Er... Janitor

General karthief

wonder how much it would cost to ship you a pair

mikestang63

ameration

General karthief

wonder how much it would cost to ship you a pair

ameration

Mustang5L5

That is…until I whipped out my Bissell

Similar threads

Engine New 5.0 Build - PCV, Breather, Both, or ????

Attachments

wonder how much it would cost to ship you a pair

lube between the nut and the face. I know my lubes

Stangnet Facilities Maint Tech... Er... Janitor

wonder how much it would cost to ship you a pair

wonder how much it would cost to ship you a pair

That is…until I whipped out my Bissell

Similar threads

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