2002 8.1 Lt Pcv Port Modification Questions

LSVLance · January 28, 2009

and I don't want to start a "Why does this engine burn so much oil" rant. I've put up with the excessive oil consumption with it for almost 7 years now and I plan to keep on putting up with it...if I can't fix it.

What I'm interested in finding out more on is my options for fixing this issue myself. I've read some snippets here and there about modifying the PCV orifice sticking out of the bottom of the intake manifold which may be a culprit in the excessive oil usage in my situation.

I'm specifically looking for pictures of the bottom of an intake like mine showing this port and also if possible...pictures of the fix that some of you may have done to this to keep it from sucking oil from the valley pan up in to the intake.

I had the intake manifold gaskets replaced under warranty when the truck had about 60,000 miles on it and it slowed the oil consumption down considerably...for about 10,000 miles or so...then it slowly started creeping back up again. Right now it's using about a quart every 1,000 miles or so. My plan is to remove the intake, replace the gaskets with felpros and thoroughly clean the new intake bolts, chase the bolt hoes in the heads, and install them using the updated TSB noted methods. But after reading about this PCV problem...I'd like to attempt to try that fix at the same time.

I'd appreciate any insight any of you that have done this trick successfully can provide.

Thanks,

Lance

LSVLance · February 9, 2009

I guess I'm just going to have to dive in to this blind then.

I'd like to do it all in one day, but maybe I'll have to plan it so maybe the truck can be down for several days to make sure to give me time to figure out what to do to the PCV port on the bottom of the intake to keep it from sucking in oil anymore.

I'd sure appreciate any tips at all from any of you that might have seen the bottom of one of these 8.1 lt intake manifolds in person.

Thanks,

Lance

redvett · February 10, 2009

Are you using the A/C Delco late design fixed orfice PCV? If not try it before you do anything else. It works and is OEM since about 2003-4.

LSVLance · February 10, 2009

The 8.1 lt doesn't use a PCV valve.

It has a port in the bottom of the intake manifold to suck the crankcase gasses up in to the intake...along with a fair amount of engine oil or so it seems.

redvett · February 10, 2009

On the valve cover there is a hose that runs to thethrottlebody with a PCV valve same as the L19 /454 engines.

The 8.1 lt doesn't use a PCV valve.

It has a port in the bottom of the intake manifold to suck the crankcase gasses up in to the intake...along with a fair amount of engine oil or so it seems.

LSVLance · February 10, 2009

Not according to several sources...

Here's one...

http://www.gm-trucks.com/forums/index.php?showtopic=54785

Also the 8100 vortec engines don't have a PCV valve.

http://www.chevyavalanchefanclub.com/cafcn...ic,15701.0.html

"1) The 8.1 does not have a PVC valve. Makes me wonder how

the oil vapors are controlled. I realize the smaller V8 has one,

and its replacement helped with the issue."

Answer: The crankcase ventilation system has no serviceable components so routine maintenance of the system is not required. A closed crankcase ventilation system is used in order to provide a more complete scavenging of crankcase vapors. The air cleaner supplies the fresh air through a filter to the crankcase. The crankcase mixes the fresh air blow-by gases. This mixture then passes through a pipe/passage located in the intake manifold.

8.1L only

I've also studied the complete engine parts diagram and there's not one on there either.

I'll admit that I haven't stripped away everything off of the valve covers themselves to look myself...but I will if you think I should.

ron7000 · June 1, 2012

I have the intake manifold off my 2006 8.1L. here are some pics.

what did you guys do?

I'm wondering if i should leave the pcv system as is, or block off the internal setup and fab up a traditional external setup.

http://www.performan...re-help-487962/

LSVLance · June 1, 2012

Wow, I've had my truck for over 10 years now, been dealing with this problem for just about as long and this is the first time I've actually seen pictures of the bottom side of my intake manifold.

The only thing I've done with mine is keep dumping oil into it. Thankfully I get my oil for free from my wifes work. ;)

I would love to see these pictures in a higher resolution, can you email them to me not all shrunk down please. lbt at attglobal dot net

That tube that is running from the valley the PVC is in up to the bottom of the intake, what is above it? Can you tell? It almost looks easier to me to add on an external PVC system than to mess with that set up.

ron7000 · June 3, 2012

that tube is the egr tube if an EGR setup was being used, but there is not.

On the rear of the intake, you can't see it with the manifold on the engine in the truck, is a block off plate. EGR piping and fixture would mount where this block off plate is and the exhaust gases would flow from there into the plenum and into the cylinders.

I'll post a pic of the top of the intake.

ron7000 · June 3, 2012

i measured stuff today. The opening in the throttle body that lets fresh air into the intake is a hair larger than 5/16" drill bit (0.3125" or 8mm).

the tube in the bottom of the intake, or orifice, I can fit a 9/64" drill bit into but nothing larger, so that's 0.141" or 3.57mm.

the more i think about it, I find it hard that oil gets sucked up into this tube. There is a metal valley tray right below it sitting between the manifold and the block, and all that's in that area is the top of the lifters and pushrods. maybe if you had a lifter bore leaking oil and flooding up into that area, the valley tray would still shield it.

in my case I bought the truck used with 70k miles, it's a 2006. it had an exhaust manifold leak and I was getting P0101 often.

the inside of my throttle body was very dirty, black and grimy. After pulling the intake I noticed all the intake runners and even right behind the throttle body was coated in a brown oil varnish. I can understand the runners leading to the cylinder head having a coating, but I don't understand how that coating made it all the way up to the throttle body.

the other thing i realized from this pcv setup, is the crankcase has to be sealed off everywhere else otherwise you have a vacuum leak. With things correct, all air entering the crankcase first passes through the air filter, then the MAF sensor, then to the 5/16" hole in the throttle body leading into the crankcase. So the pcv air is metered by the MAF. if air enters the crankcase elsewhere then it is not metered by the MAF and is a vacuum leak and will cause problems. these areas are the oil dipstick tube into the block, and even the dipstick into the dipstick tube- there is an oring on the yellow ring of the dipstick. Also the oil fill cap and the plastic fill tube going into the intake. And gaskets elsewhere- oil pan gasket, valve cover gaskets, and intake manifold gaskets obviously.

ron7000 · June 4, 2012

and I don't want to start a "Why does this engine burn so much oil" rant. I've put up with the excessive oil consumption with it for almost 7 years now and I plan to keep on putting up with it...if I can't fix it.

have you looked into other reasons into oil consumption?

Do you know if you are burning oil? Do the spark plugs show signs of oil burning and do you have blue smoke in the exhaust?

when i got my truck the oil cooler lines were seeping where they have the crimps. i didn't drive mine enough with it like that, but i would suspect with engine off and parked there would be no oil loss and no signs of oil under the truck. But with engine running and driving down the road oil can seep out through the lines and you'd never know other than by the low reading on dipstick next time you checked.

LSVLance · June 4, 2012

When I had the intake bolts TSB done, it slowed down the oil consumption quite a bit..for about 10,000 miles or so...then it's continually gotten worse again after that. I noticed the last time I changed the oil that I've got a leak somewhere on the drovers side of the block as well which I assume is the oil cooler lines. I drive the truck every day and get my oil for free...so I haven't taken the time to fix it properly yet.

Now that I know what the bottom side of the intake looks like (thanks for the pictures) I'm developing a plan. I think what I'm going to do is pull the intake, cap off the orifice, then reseal the intake real good using fel-pro gaskets and the new style bolts. Then I'm going to rig up an external catch can PCV system to pull pressure from each of the valve covers. While I've got it all tore down I'll probably replace the oil cooler lines as well.

I just need to come up with the parts...and enough time to get it all done with minimal downtime of the truck.