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Positive Crankcase Ventilation PCV Direction

  • Thread starter Thread starter gregski
  • Start date Start date Jul 24, 2010
G

gregski

Active Member
Mar 13, 2010
577
0
28
Sacramento, California
Jul 24, 2010
#1
  • Jul 24, 2010
  • #1
I did a search for this and came up short, so I figure I will ask a newbie question. When looking at the first generation 302 Mustang engines and comparing them to the second generation Mustang II 302 it seems like the Positive Crankcase Ventilation PVC direction is reversed. So does it matter which valve cover holds the breather and which has the PCV valve, and simply can the covers be swapped from left to right? (physically they seem to fit on either side)

On the first generation the air enters the air cleaner then comes out of the front of the cleaner through a rubber hose and down the driver side valve cover into the cylinder head and into the block, through the oil pan and up the other side through the block, past the head, out the passenger side valve cover, by the PCV valve through another rubber hose located in the BACK of the engine and into the carburetor spacer or the base of the carb itself. See first picture below.



On the second generation the air enters the air cleaner in the back of the engine then descends down the passenger side valve cover into the cylinder head and into the block, through the oil pan and up the other side through the block, past the head, out the driver side valve cover, by the PCV valve and into the carburetor spacer or the base of the carb itself in the front of the engine. See schematic diagram below:



Why do I care, why am I asking?

Well in the process of removing all of the SMOG stuff off of my 1976 engine I would like to use a non EGR intake with non EGR carb spacer and I don't want to have to run a long rubber hose from the front of the driver side valve cover all the way to the back of the carb spacer in the back of the engine, if I can just swap the valve covers then the PCV port will be on the back of the valve cover closer to the port on the carb spacer. See the current and proposed valve cover, carb spacer layouts on concrete below.





For the inlet I just plan on using a breather cap, (since I don't own a stock air cleaner, and will probobly opt for one of them round chrome jobbies with no inlet nipple on it), so I am mostly concerned with the PCV valve side as it tends to spew oil.
 
2

2+2GT

10 Year Member
Apr 25, 2009
3,333
10
79
Southeastern Pennsylvania
Jul 24, 2010
#2
  • Jul 24, 2010
  • #2
Actually, the change started around 1971, with the PCV moving to the oil filler cap on the left-front corner of the engine. It doesn't matter which way the air moves, though, assemble it however you like.
 

horseballz

10 Year Member
Sep 30, 2009
824
19
49
Las Vegas, NV
Jul 24, 2010
#3
  • Jul 24, 2010
  • #3
gregski,
I must compliment you on a very clear and thorough understanding/explanation of the PCV system. As previously stated it doesn't matter which side/direction, but if you live in a smog test area, you need to have the breather side go to the air cleaner. Most after market air cleaners have a knock out on the bottom for this purpose.
Happy Oil Fume Sucking To Ya,
Gene
 
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