1993 valve cover CCV fitting

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Eric Haberli

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Does any one know what the orifice hole size is in the CCV fitting that is installed in the 1993 valve cover I have replaced my 1990 2.5 crappy plastic valve cover with an Aluminum 1993 valve cover and it works fantastic.
The 1990 PVC says its opening is 2.2mm. I am wondering, is the fixed orifice in the Aluminum cover too small? Especially with this being a 1990 with a TBI system???
 
90/2.5L/m/t

yes, some jeeps run a fixed orifice. (the i6 allows that) some use a check valve. so if 4cylinder that is very different engine PCV .

my first ever, jeep 88 4.0L had an orifice only PVC, (CCV)
keep in mind is it is A loop. one side is clean fresh air (from air cleaner stolen from)
and the other end is PCV (check valve or and orifice) that sucks out the crankcase fumes.
mixing up engine parts can be hard.
93 over 90 engine, mix. i4 only
lets see what the OEM FSM says about both engines.
free to read in the sticky.

the hard part of cars, is the books do not go into the design of the engine nor PVC, details very well.
the best way is just do your own examinations of each stock part and learn what is really there, even buy new part for it, so wrong parts there now are removed first. (many jeeps are hacked up with wrong parts or worse clone junk from 12k miles away.
the FSM covers 3 engines so 2.5L is it.
chapter (0) zero PVC
page 18 here it is 90
as you see the fresh air hose is bottom right.
the PCV (real a check valve works best) but the orifice kind love to fail. (not just clogged even prefect it fails)
why well the loop can reverse, with bad rings (piston) and over whelm the silly Orifice.
and then blasts. oil fumes to the was clean air filter.
now that you know that, what works best for you? is based on blow-by gas rates on very old engines.

90.JPG



next the 93 same PCV loop details, from the real OEM FSM manual. free.
the fitting top left is an orifice too. (fitting)
0-20 ch0,page 20
if bypass gasses are too much, ream out the orifice. (do not allow crankcase pressure go too high or seals leak or fail.)<<< old old engine answers.
if engine is very good the 2.2mm is spec, run that. I will now measure mine, 95. and post. next.(soon)

93p.JPG
 
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95' (and 93)#42 drill fits, 0.082" x 25.4 =2.08mm
lost my 43drill but 44 fails,
you do the same get what is there actual
makes sense all 2.5 the same. to me.


43 = 2.26mm
might fit or not. IDK
but just run stock orifice.
my PVC is solid brass,. drilled out. simple crude orifice.
and alum, alloy VC
 
I do have a complete set of the 1990 FSM's. I noticed reading the FSM that the 1990 PVC valve had an opening of 2.2mm. So I started to think that I now have the aluminum VC with the orifice CCV that maybe its not big enough in Dia.?
 
engines that are old (omg 30) have huge blow-by past the rings.
and overloads any PCV, orifice type or the check valve type,
then the fumes, back up to the air cleaner box. (and make it a huge nasty mess)
this is well known on all cars for 1950s up the day blowby draft tubes were banned in the USA by the EPA>
nothing new here. just blowby,
go to 3mm hole. ?

my 95 has stock intake system does yours
mine runs fresh air to valve cover (facing it) on the top left molded hose. if this blows to Air cleaner the element is wrecked.
the yellow arrow are normal flow.
if PCV clogs it REVERSES this is the fresh air path, filtered clean air side

cleaner (1).jpg
 
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one more trick move the hose seen above too the nipple on top smaller, it musts be drilled out first as mine is blocked inside. (hose reducer coupling)

then those fumes, now make the TV VALVE a nasty mess. in the TB bottom.
saving the air cleaner element. I say may. It depends on the smoke cloud size and volume.
now trick 2 and 3
newer cars have a box called the PCV buffer chamber that cures this or with heater (has a cooling system loop in the PCV chamber)
it heats the cloud so it does not make huge oil slick.

my 88 4.0L XJ, had PCV gauze filter area on the rear of the Air cleaner box to stop this act. (but needed cleaning time to time))
prevents the air cleaner from getting wrecked.
jeep decided we don't need it.
 
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know a guy that made a large chamber. or a box 2x6" with lid or a small metal cookie box? 2inches tall.
2 ports for hoses top
top comes off later for cleaning.
2 nipples added to the lid and fumes condense inside ,
bottom of box to face earth(road) even put gauze inside,

it came apart for cleaning. used on high mileage engine, and sure banned in calif, smog inspections. visual
good luck to you.
 
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