Head scratcher

[L31MaxExpress]

Well wish me luck, headed on a 100 mile drive here shortly. I have put about 300 miles on it since I put the 4L85E back in it and seems to be driving well now. Checking over everything I did have to add a quart of oil to it so it has been burning it, was low to start with, or the stick is not marked accurately. It is hard to get an accurate reading anyway on a 5' long stick by the time it has dragged through the length of the tube. It has a 5 qt pan and a 1 qt filter, I put 7 quarts in it when I changed it because I also added the OE oil cooler back on it at that point and never pulled the stick. Oil life monitor is still showing 80% oil life remaining lol. Cool feature that was in the P59 L31 calibration in the GMT800 trucks. Change the oil at ~10% life remaining, key on engine not running, smack the pedal to the floor 3x in 5 seconds and it resets. The OBDLink software displays the oil life remaining on my 10.1" Android touch screen head unit, pretty slick.

 

[L31MaxExpress]

Trip was un-eventful. Drove great for the most part. I do need to mess with shifting a bit more, it tends to upshift to 3rd and 4th too early under moderate throttle and lockup the TCC in 4th too early still. Some how I have it holding TCC lockup down to 50 mph in 4th and the cam really hates that. Before leaving I threw the PCM into MAF only mode so that I can re-dial in the MAF transfer function. With a GM 525 HP LS3 MAF calibration interpolated into the P59 it ran at +/- 3% average fuel trim error. I saw it about 3-5% lean in PE in the midrange. At one point I had the cruise set at 82 mph in a bunch of rolling hills and it stayed in overdrive with the converter locked at ~2,500 rpm pretty much effortlessly. Math in my HP Tuners scanner setup showed ~15.5 mpg, it is pretty accurate too. I had a lot of traffic on the way out and there are numerous traffic lights on the way to the open highway section. So all in all I am happy with that.

 

[Sean Buick 76]

Nice work

 

[L31MaxExpress]

Nice work

Not too shabby if I must say so myself. With the line to lube mod done on the 4L85E it actually runs about 10°F cooler cruising down the highway than it did before. It was 100F outside and the trans temp was glued at 160F for the most part. It actually dropped toward 150F running 80 mph with the cruise set after the converter had been locked up for a while. As I got closer to where I was heading it started getting dark and the ambients dropped into the upper 80s well outside of concrete jungle of DFW headed northwest. The trans temps dropped even more down to the high 140s. Coolant temps and IATs dropped as well and the engine started running even stronger. Stock radiator cooler with the M7B plumbed after it has been a great cooler setup for me and the line to lube just enhanced its cooling ability.

In the morning I want to look in the catch can just to see if anything has actually made its way into it yet. I opened it last night after my 20 mile trip and it had a very slight oil film just starting to form near the inlet from the PCV valve, but it was brand new hoses as well which will condense some of that oil vapor which will cling on the inside of it before allowing oil to reach the seperator. I want to monitor that situation atleast every fill up for the next 1,000 miles to get an idea just how much of that oil on #4 was from the PCV. It could easily be other issues but I hope not. If it turns out that it is not much, I will be sure to pay close attention when the intake manifold comes off. It is possible it is pulling air from under the intake valley as well. I have been meaning to cap off both the PCV valve and vent hose, cap one of the grommets in the valve covers and covering the 2nd with my thumb to find out if it has an internal vacuum leak. I might do that, remove the valve covers and play with the lifter pre-load again if we have a nice cooler day in the next 2 weeks or so.

 

[Pinger]

Nice work

Yep. And the sharing of it adds to the body of knowledge.

 

[L31MaxExpress]

Yep. And the sharing of it adds to the body of knowledge.

Very true.

Also to add to that, I feel I can say that the PCV was a very signifigant part of any oil being burned by this engine. This was after 120 miles on the catch can install. It also has the fixed orifice LS PCV on it that GM designed to help with oil consumption by limiting flow. The catch can has oil rolling around in the bottom of it. Actually more than even I thought there would be. Before the catch can and PCV vacuum source change most of that would have been finding its way down the #4 intake port.

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[0xDEADBEEF]

That's a lot for 120 miles. That's roughly what I get from a whole track weekend at COTA.

 

[L31MaxExpress]

That's a lot for 120 miles. That's roughly what I get from a whole track weekend at COTA.

The valve covers have stock like baffles in them. Kind of weird that it is pulling that much but it was being run pretty hard at times despite just cruising. 6 of the steeper, longer grades have climbing lanes on them and I had the cruise set at 80. It was spinning 2,500 rpm the whole time.

Makes me wonder if the PCV vent side needs a catch can now as well. I could easily mount one on the opposite side of the core support and do the same for it. I do see some slight oily buildup on the plastic Vortec hat and the throttle body gets an oily film built up inside of it. The engine itself seems to have very little blowby. I checked it before and at idle the little fixed orifice PCV was pulling 5 in/hg on the crankcase at idle measuring with a vacuum gauge on the vent port and about 7 in/hg @ 2,000 rpm and no load. That made sense to me since the engines manifold vacuum increases from about 13-14 in/hg @ 750 rpm to 21 in/hg @ 2,000 rpm. That PCV setup is probably pulling a lot of the oil on deceleration or coasting down grades at 2,500 where the engine makes 25+ in/hg vacuum. I might try a stock PCV valve after I get a feel for what it is pulling into the catch can over the next 900 miles. Then repeat that test with a stock PCV valve. It is an inexpensive simple change and will either make it better, make it worse or stay the same. I do not see the need to go to one of those overpriced adjustable setups on this when cleaning a little oil out of a catch can is easy and far cheaper.

 

[Road Trip]

Also to add to that, I feel I can say that the PCV was a very signifigant part of any oil being burned by this engine.

Over the years we had a stroker engine where a catch can was the solution to a similar issue. And currently we have
another one (that gets wound to ∞ ) where I'm going to refresh the rings -and- put a catch can on it also.

One possible reason I think why catch cans are becoming more popular has something to do with us increasing
the piston displacement while at the same time being forced to do this in the same total internal volume defined by
the block. Back in the '50s there was a 265 or 283 worth of piston displacement stirring up the internal volume.
(And a no-resistance road draft tube to relieve any pressure from imperfect piston ring seal.)

Fast forward to today, and we're grinding the inside of the block in order to make room for a stroker 383.
Or running a .030" over 406. And yet we're doing so in the same internal case volume as the old 265/283 motors.

Now some will jump in and state that the 'average' displacement inside the engine remains the same (one piston
going up while another is going down) but since the air is still being pushed around by the bottom of each piston,
there's going to be a lot more 'slinky-style air movement' between cylinders that are 180° apart from each other
in terms of crankshaft rotation. With enough added 'excitement' inside the engine, there's no doubt that there's
more oil vapor in the air, so as the blowby from the piston rings is evacuated via the PCV valve, there's going
to be more tiny oil droplets leaving via this path. Ergo the need for a catch can.

Note: A side effect of our added displacement is that there will be more vacuum on the intake side of the PCV valve
for a given vehicle at a given cruising speed. Even assuming the same state of tune, a 283 pushing a van down a
TX interstate at 80 mph is going to have a lower intake manifold vacuum than a 383, given the same gearing & all that.
So, more intense pressure pulsing on the same size crankcase on one side of the PCV valve, while at the same time more
intake manifold vacuum on the other side of the same valve? Sounds like a recipe to need to add an oil/air separator
in line?

Given all of the above, adding a catch can to the mix makes sense once you think about it. Sure, the first thing that
comes to mind is to double-check the piston ring seal. But if you are already getting stellar leakdown rates, then we have to
stop & give some thought to what we're asking of this architecture. We're a long way from a 283, Toto. :0)

 

[0xDEADBEEF]

The valve covers have stock like baffles in them. Kind of weird that it is pulling that much but it was being run pretty hard at times despite just cruising. 6 of the steeper, longer grades have climbing lanes on them and I had the cruise set at 80. It was spinning 2,500 rpm the whole time.

Makes me wonder if the PCV vent side needs a catch can now as well. I could easily mount one on the opposite side of the core support and do the same for it. I do see some slight oily buildup on the plastic Vortec hat and the throttle body gets an oily film built up inside of it. The engine itself seems to have very little blowby. I checked it before and at idle the little fixed orifice PCV was pulling 5 in/hg on the crankcase at idle measuring with a vacuum gauge on the vent port and about 7 in/hg @ 2,000 rpm and no load. That made sense to me since the engines manifold vacuum increases from about 13-14 in/hg @ 750 rpm to 21 in/hg @ 2,000 rpm. That PCV setup is probably pulling a lot of the oil on deceleration or coasting down grades at 2,500 where the engine makes 25+ in/hg vacuum. I might try a stock PCV valve after I get a feel for what it is pulling into the catch can over the next 900 miles. Then repeat that test with a stock PCV valve. It is an inexpensive simple change and will either make it better, make it worse or stay the same. I do not see the need to go to one of those overpriced adjustable setups on this when cleaning a little oil out of a catch can is easy and far cheaper.

If it's consistently just normal looking engine oil, I wouldn't consider it an engine health issue and more of something that needs to be corrected or improved on.

I agree with @Road Trip that your engine is probably pulling a lot more than that orifice was designed for. Another thing is if you have aftermarket rockers, they could be slinging oil everywhere. Some of those designs are big and blocky and I think they whip the air around more in addition to that. Also, if you've done something like a high-volume oil pump there's going to be more oil pumped up top.

GM didn't really fix the issue on the LS until they put the PCV in the valley cover, but even my C8 with a dry sump I still see oil in the can.