Getting rid of the PCV line?

[deth_1970]

think of it this way, you have compressed burning gases on one side of the ring, and a mild pressure on the other side of the ring, while it is moving down the cylinder those 2 pressures are working against each other, so you don't get maximum pressure on the ring from the combustion and power stroke,

with the PVC hooked up, there is a vacuum in the block, so there is a negative pressure under the ring, causing the ring to be seating better against the cylinder wall due to compressed burning fuel, and less blow by, unless the rings are worn out

[motornut]

i've understood it sucks out the "blowby" as the rings etc wear out
with no vent, the pressure will prob blow out your gasket some where

I just replaced my "paper" vent on the 78's drivers side,
but it's already dribbling out and down....

(old pic)I ran a old rubber hose bit down the back in my old 81 lemans with the 229
my second exhaust pipe lol

[Firebirdjones]

Originally Posted by Corts60

No it is not. What deth_1970 said is correct. The PCV keeps a vacuum on the crankcase to keep vapors from building pressure. That is why it is called POSITIVE crankcase ventilation and not just crankcase ventilation. Those old tubes were not "dump tubes", they were downdraft which drew a vacuum on the crankcase and they were not emissions devices at all. That is what PCV replaced because it was a way of achieving the same goal as the downdraft by ventilating the crankcase and also being better for the environment.

You are taking what I said out of context. In one sentence you say it's not an emissions device, in another sentence you say they were better for the environment.

I had also mentioned vacuum and positive crank case evac in another post earlier. Put it all together and I think you know exactly what I was trying to explain before

[Firebirdjones]

Originally Posted by Number21

So there's potentially a HP/gas mileage gain with the PCV?

Well,,,,not really. Now we're are splitting hairs There is a vacuum draw there, only at idle and light throttle though. Keep in mind there is no vacuum draw at full throttle so the PCV is assentially inop. So when you would think a vacuum draw would be most needed,,,,it's not there There really isn't enough of an affect there to argue whether a PCV helps ring seal or not. At idle or part throttle it's not so much of an issue.

The only time I've seen an improvement in mileage and performance is one of two things. You either run a catch can to trap any oil vapor that makes it into the PCV system before it enters the intake,,,or simply remove it all together.

You won't find a PCV on any type of performance engine built for racing. Pumping oil vapors back into the intake track is a no no. Most of the time it's simple open breathers.
What you might see on the more serious pieces are dedicated vacuum pumps (they vent to atmoshere too) or you'll see a cheaper version with hoses running to the exhaust system to draw a vacuum (again it's going to atmosphere too ) These setups are generally used on engines built with low tension rings (meaning less drag) and/or smaller ring packs (meaning less drag) that need extra assistance in ring sealing. There is also some HP to be found in these instances. On a street engine with a standard ring package,,,it's negligable at best.

We are talking about your basic stock street engine in a truck. Alot of this trickery is beside the point. What it really comes down to is whether your area has an emissions test with a visual inspection. If not then I'd do as you wish and not worry about. Or better yet, experiment and see what you like best.

[Number21]

Originally Posted by Firebirdjones

What it really comes down to is whether your area has an emissions test with a visual inspection. If not then I'd do as you wish and not worry about. Or better yet, experiment and see what you like best.

No inspections around here, most have to go through smog but I don't with the '73.

At the very least I think I'm going to get some new valve covers and move the holes, whatever they may be, to the front.

Thanks for explaining it everybody.

[Firebirdjones]

Originally Posted by Number21

No inspections around here, most have to go through smog but I don't with the '73.

At the very least I think I'm going to get some new valve covers and move the holes, whatever they may be, to the front.

Thanks for explaining it everybody.

Just out of curiosity,,,how far back does Oregon go on the smog testing? I bought my truck (many years ago) out of Battle Ground, Washington just on the boarder there.

[Number21]

'75 and up have to be smogged, with a visual check for a cat. That's why I love the 73-74s. My old '79 one ton was exempt too, at 9000GVW. Had to get rid of another '79 I bought because I couldn't pass emissions.

[Firebirdjones]

Originally Posted by Number21

'75 and up have to be smogged, with a visual check for a cat. That's why I love the 73-74s. My old '79 one ton was exempt too, at 9000GVW. Had to get rid of another '79 I bought because I couldn't pass emissions.

Thanks. Yeah my 79 1 ton is exempt too. It never had a cat from the factory (9000 GVW like you said) but it did have a smog pump. I removed that when the headers went on.

[irishman999]

I see the question has been answered already but thought I would share anyways. I took my PCV valve out when I first got my truck because I thought it was just "emissions crap". I could never get the truck running right no matter what I did. For a year and a half I chased this performance issue and threw parts at it. New Carb, new intake, phenolic carb spacer (thought it might be vapor lock), new distributor, 2 new fuel pumps and some other stuff I am forgeting.

After all this BS my dad plugged in a PCV valve he had sitting in his shop and the truck immediately ran perfectly like it was fuel injected, every trace of the problem was gone.

[Number21]

Originally Posted by Firebirdjones

Thanks. Yeah my 79 1 ton is exempt too. It never had a cat from the factory (9000 GVW like you said) but it did have a smog pump. I removed that when the headers went on.

Yeah, I always thought that was weird the 1 tons didn't get cats unitl later. I had to argue about that one for my emissions test, but I failed anyway...

[Firebirdjones]

Originally Posted by Number21

Yeah, I always thought that was weird the 1 tons didn't get cats unitl later. I had to argue about that one for my emissions test, but I failed anyway...

Small world. I've been through that too. Seems the youngins they get to run these smog stations aren't aware that cats were exempt on anything over a certain GVW throughout the 70's & 80's. You would think holding a job like that would require these people to be educated on that stuff.

I thought it was common knowledge and didn't really think anything of it at the time. I actually had to bring down old factory literature to convince them.

[1977K10]

Don't feel bad of the right side of my block, it goes to a short hose into the air cleaner as well, and that has filled my air cleanr with some oil and alot of residue as well.