PCV Valves

[kdmranch]

I noticed that the PCV valve mounting hose was all punky on the 90. I was lucky enough to have one on hand. But while I have this apart I thought I would change the PCV valves also. Must I find LT-5 specific valves or can I just match them up by dimension at the local NAPA? Would the 91 have the same valves? Dont want the girls to get jealous of each other,;)

[kenthompson]

I noticed that the PCV valve mounting hose was all punky on the 90.

Is "pucky" a technical term that I need to learn to work on my car? :)

Seriously, they say the valves have different springs in them so that they open up at different times. When I rebuilt mine, I just used the same valve on both.

[bradslt5]

there are definatly 2 different pvc valves . youd have to ask jeff if they really makes a difference on if you can use others also there is an order that they are placed

[Jeffvette]

Part numbers are:
CV769C Left Hand side
CV913C Right Hand side


And the reason for two PCV valves from Graham Behan:

"Well as in most of the stories from the early days of development it is
a long'ish one. Yes the system is the way it is based partially on cost. The
fresh air recirculation type of system utilizing PCV'S was the way that most
GM products were and the way that the LT5 was specified. The problems with
this were that with the LT5'S relatively high output coupled with the lack
of internal crankcase volume the requirements for the PCV system was very
different from the norm . The engine exhibits very different characteristics
at part load/no load than it does at WOT, this is true of most engines but
the massive blowby at no load required a very different PCV characteristic
than the WOT condition. During the development process Allan Nobbs, of
Lotus, came up with a variable orifice PCV valve which was well suited to
the large changes in the engine. Well after the design was shown at one of
our many vendor meetings it was decided that tooling a completely different
valve was not on, so the system was changed to the current spec, using two
valves with differing characteristics in an attempt to establish a good
compromise. We can all see the results, the system actually exhibits reverse
flow at WOT."

[bradslt5]

one question that I have allways had . does it really make a difference if you dont have the pvc valves in the correct order?

[bradslt5]

if one was using the car for the strip only is there a better set up

[kdmranch]

Is "pucky" a technical term that I need to learn to work on my car? :)

Seriously, they say the valves have different springs in them so that they open up at different times. When I rebuilt mine, I just used the same valve on both.

The term is "punky", not "pucky". I think that is a highly technical term, {as you had noted} that I am very sure I am not qualified to use.:D

[kenthompson]

The term is "punky", not "pucky". I think that is a highly technical term, {as you had noted} that I am very sure I am not qualified to use.:D

Oh yea, that's right. Pucky is what my DAD used to call a tube of silicone. Highly technical term

[Bob G]

What is the better set up for the strip ? thanks Bob

[A26B]

one question that I have allways had . does it really make a difference if you dont have the pvc valves in the correct order?

No, just as long as both valves are correct.

[bradslt5]

thankyou jerry .i allway wondered about if the order was manditory:thumbsup:

[petefias]

What is the better set up for the strip ? thanks Bob

Strip, as in removing clothes? :)

[bradslt5]

could one use breathers instaed of having the system closed . if the car was going to be used as a drag car only

[flyin ryan]

could one use breathers instaed of having the system closed . if the car was going to be used as a drag car onlyyour better off keeping it closed & at least try to keep some negative pressure (vacuum) in the crankcase. you won't have any manifold vac. at W.O.T. of coarse, well next to none, but you will in the staging lanes & after your burn-out. will an open system (breathers) you'll never have any crank. vac. at any time. the whole idea is to keep the cylinder walls clean, the rings stable & keep the oil away from the rotator (crank, rods). with breathers you may not build up any pressure but you'll never build any crank vacuum either & that's the goal. on the better stuff i do, 2 H.P. per cube & up, i generally turn the rear main seal around, backwards, because i'm trying to run so much crankcase vac. it will flatten out the seal & pull in fresh air. this way the more water depression, vacuum, it will tighten up on the crank. that how important vacuum is to me. it's kinda a tough deal with the LT-5 having so little volume but venting into the atmosphere is not the answer if a guys looking for power, IMO.