Oldvetter

My 98 C5 with 101,000 miles on it uses no oil between 6,500 mile oil changes (near 0% on DIC).

Only broken part has been oil sensor. When I replaced it, I noticed a lot of oil on the intake manifold.

I have been researching this, and know that a lot of people install oil catch cans. BUT, I also came accross a new GM PCV Valve, part number GM 12572717, which is supposed to eliminate this problem. I bought it ($9) and it is a PCV Valve without any check valve and has a very small (1/8 or 1/16 inch dameter) hole in it. It flows MUCH less than the normal PCV valve.

Can someone tell me the pro's and con's of using a catch can verses the new PCV valve?

Todd157k

There have been a couple threads on it. Do a search "catch can" and look through. I remember someone mentioning that pcv valve before and, if I remember correctly, disregarded it because it built more crank case pressure and didn't separate the oil OUT of the system. Besides, the catch cans look so much better!

Dave68

PCV (small orifice) = ?
PCV (variable flow) = good
Catch can = better
Coalescing filter = best

See http://www.conceptualpolymer.com/PCV...oval%20101.pdf

for more info and relevant link.

Oldvetter

Dave, I read your link, it is great.

I also found this on another Website:

"98-02 LS1 GM PCV Valve (New Design)
[12572717] $6.99

As many of you know, the PCV system on the 98-02 LS1's isnt exactly the greatest system on the planet.....burning up to 1 quart every 3K miles. After many complaints, GM finally issed a service bulletin to address this issue on all of the GEN 3 engines. They have replaced the ball-type PCV valve with a new fixed orifice design that is used in the GM trucks. This design will help reduce oil-consumption on your LS1."

And with the small (1.27 to 1.31 cfm) airflow you measured, I don't see how even a small hole in the PVC would be "?", especially after GM approves it use?

Dave68

Oldvetter,

From what I have read so far, this PCV valve is recommended for these vehicles:
1999-2002 Silverado, Suburban, and Tahoe
1999-2002 GMC equivalents
2002 Avalanch and Escalade

The new valve limits flow to the intake, reducing excessive oil consumption in those vehicles that are suffering from this condition. The new valve will probably reduce oil liquids from flowing down to the intake, but it will not stop oil aerosols (and I believe the result of which is what you are seeing in your intake).
Therefore, I doubt that this would help your condition. Even catch cans do little to trap the majority of air-born oil. Only a true coalescing filter can do that.

For more info regarding the new PCV valve, see:

http://www.mightyautoparts.com/pdf/articles/tt122.pdf

Oldvetter

Dave,

-I read your link.

-It said to check line for liquid oil before installing. And with your opinion that my problem was oil vapours, I thought I would try a test.

I removed my PCV valve on my cold car to check for liquid oil, none found. I drove for about 5 miles (I have a MN6) leaving off of the accelerator at about 3,000 - 4,000 rpm and coasting (to create a high vacuum situation). I checked my PCV valve, it had a surprisely amount of liquid oil on it. Now, most of this would have drained back into my engine, but some must have been sucked into my intake.

I installed the new PVC valve.

Dan_the_C5_Man

This new "fix" from GM is kind of like the column lock debacle.. What costs less, a re-designed PCV "valve", or manufacture and install an external catch can to solve the problem?

Having seen first-hand how much oil is accumulated during hard driving over a short period of time, I respectfully disagree that airborne oil vapors are the primary component; assuming current production catch-cans really aren't very good at filtering the small stuff, they sure catch a lot of oil despite "inefficient" operation.

drivinhard

Just ordered an Elite catch can this week, will install next week

Dave68

I was referring to those engines that have much lower blow-by than is normal. Most of us cannot go 6500 miles without using any oil. Remember, too, that a coalescing filter will trap the liquid stuff as well. Its advantage over a catch can is that much more of the oil aerosols
are trapped by the much more dense borosilicate glass fibers in the coalescing filter. It's kinda like comparing the original Vararam filter to a Blackwing or Halltech filter - the old Vararam did catch the big stuff, but the fine stuff easily passed through it. The Blackwing and Halltech catch everything. You may have to clean them more often, but your engine will be thankful for it!

Dan_the_C5_Man

We are on the same page.. I plan to eventually look into replacing the filtering material shipped with my can for something a bit denser.. Any chance you have a lead on raw materials? I'm sure it wouldn't be as effective as the setup you’re running, but based on your airflow measurements I am now less concerned with flow restriction.

Secret237

I plan on going with Dave68's coalescing filter and the new PCV valve.

Thanks Dave

Oldvetter

Plesase let us know how much oil your filter catches ater the new PCV valve.

Dave68

Dan,
I did look into having a custom coalescing filter made for a made-from-scratch setup, but the only company I could find that does this, does not want to deal with anything less than a large company that would order thousands. You can buy replacement low-flow filters from Watts for about $25, but you'd have to make sure your upper piece is threaded to accept the hollow filter stud. However, as you know, doing more than a small amount of modifying quickly eats up any advantage over just buying the real deal.

Dave68

Secret,

The new PCV valve was designed for vehicles other than the C5, according to the list I noted in an above post. Still, it may very well reduce the amount of liquid oil that gets into the LS1 and LS6 intakes. Fortunately, this will be a good experiment, as it should verify my claim that oil aerosols will still flow beyond the new PCV. Remember that the first sign of visible oil at the bottom of the new Watts will take a while, compared to after the filter element is fully saturated. Give it approx. 400-500 miles before you check for the first time.

Dave

Bell

Dave68,

Your aritcle is very comprehensive.

Three questions; 1) on page 5, you give the flow and temp numbers but never mention the pressures you measured. 2) Can you post a website link or give us a phone number to contact Watts or Parker? 3) Did you make the extended body yourself? Do you know of a source that can provide something that works for those of us don't have the tools to fabricate something like that?

Thanks.

Dave68

Thanks, Bell,

1) I measured 20 inches of mercury vacuum pressure, which is equal to approx. 10 psi.

2) I bought my Watts from Numatic Engineering at 800 247-2957. Retail price is about $55, but if you work for a company (as I do) that regularly buys from this distributor, discounts are available.

3) Yes, I made the extended body, myself. The drawing I used is on my website at
http://www.conceptualpolymer.com/corvette_c5_corner.htm.
Keep in mind that I have pressure-checked this design to 60 psi. It is intended to be used for this type of application, which involves far less pressure. I purchased a bunch of these from a machine shop for a little more than $30 each. The zinc body that comes with the Watts coalescing filter can hold 1 oz, so if you don't mind emptying it every 1000 - 1500 miles, you can always use it, instead. However, it'd be best if you can have someone make one as per my drawing.

Dave

Bell

Dave,

Do you mean you purchased a bunch of the extended bodies for $30 each? Assuming you only need one on your car, are you selling them?

HeadHunter1

It may be a fluke, but I have both a 2003 Z and a 2006 GTO with an LS6 and LS2 respectively. The Z is supercharged with both catch can setup and a breather oil cap. The GTO is naturally aspirated with the catch can and without the breather.

Technically on the FI setup in the Z, I would expect greater crankcase pressure and therefore more oil getting to the catch can. That is not what is happening. The motor with the breather gets very little oil in the catch can where I fill the one on the GTO every 5000 miles.

Could the breather cap help reduce the amount of oil headed towards the intake? I will be testing this soon by getting a breather cap for the GTO. If the oil caught in the catch can reduces significantly, this may be another cheap solution.

Oldvetter

You could just be blowing the oil out of your breather. Is there evidence of this around the breather? Check the hood liner (if you have one) over the breather and items near it for an oil film.

Dave68

Bell,

A while back, I asked if anyone would be interested in my ordering a minimum quantity of these extended cans. 17 people responded and I placed an order for 17 cans and 19 Watts coalescing filters (2 people are getting just the Watts with OEM zinc body). At this time, they are all taken, so in order for me to place another order at the $30 price, I'd have to have 10 additional people interested. Once a machine shop sets up a CNC lathe, they don't want to break it down until the entire run is complete. If I were ordering 100, the setup cost would be minimal compared to the total dollar amount. By contrast, if I ordered one can, the cost of setup would represent the biggest part of the total cost.
Also, I offered to do this without adding anything onto the prices of the parts. Since I am not a supporting vendor, it wouldn't be fair to those who are if I were making a profit. Plus, I feel that many here have helped me out in the past; this is my payback, so to speak.

Dave