I know most of the things that could lead to burning oil, but I am looking for what the most likely culprit could be. For back story this is a 5.3 LM7 that I torn down to the bare block. It was professionally honed, the crank was polished, and I had new cam bearings installed. I put it the rest of the way back together with new gaskets and rings from sealed power. I reused the pistons and connecting rods. The engine has run perfectly since it was put back together last June.

This weekend I took it for a short drive and brought it back home and parked it while I went inside and left it idling. When I came back out it was putting out a significant amount of blue smoke on the left bank only. It has a true dual exhaust with no crossover pipe. I pulled the plugs and the plugs on cylinder 1 and 3 are wet with cylinder 3 being the worst. I plan to do a leak down test when it stops raining.

I know the things it could be. But I'm wondering if there is a more likely culprit. I would love for it to be something straightforward like a head gasket. I really hope it isn't the rings.

 

Did you have the heads reworked ? Maybe valve guide/seals are bad

 

I’ve seen a wonky PCV setup put oil in the intake, causing this very scenario, many, many times.

 

Yes, I disassembled the heads and had the seats and stock valves cut/ground. The seals are new, reused the guides.

Wouldn't the pcv show up in both banks? I know it feeds into the intake on that side but I would expect faint smoke on the passenger side bank. I can try plugging the intake and exhausting the valve cover to atmosphere though.

 

I guess I can give more specifics about the engine. It's NA with a stock LS1 cam. Truck manifold, DBC, L59 injectors, terminator x standalone, SM465 manual trans. It's in my 86 K30 so I haven't really been flogging it.

 

Chased an oil burning issue myself thinking it was PCV related and after venting the crankcase to atmosphere it was still oiling the intake and fouling plugs. Have you ran compression and a leak down test on that side of the engine yet? That should tell you if it's the valve seals or the rings.

 

No. I just ordered the leakdown tester from Longacre Racing. I keep the truck at my family's farm which is about two hours away. I only go down there to mow grass and work on the truck every two weeks or so. All my troubleshooting will be next weekend. I bought a new PCV valve just in case. I misunderstood the PCV system. I thought the baffle in the valve cover behaved like a reed valve. I didn't realize there was one in line on the hose.

 

I had a set of heads the machine shop setup the install height wrong and I got valve float. The inner spring ended up pulling the valve seals off and would smoke terribly on decel.

I no longer let a machine shop set up my heads.

 

Let a guy do some work to a set of PRC 265CC LS7 heads for me once. He said they didn't do a good job of deburring the guides so I agreed and paid him for his work. It was only after learning how to disassemble them myself that I found he had tossed in some LS1 valve stem seals where there was Viton seals for the bronze guides and my Manley LS7 titanium intake valves were replaced with LS3 hollow stems. It got so noisy I was afraid to run the engine anymore and when I learned what he had done of course he denied any wrong doing and blamed TSP for putting in the wrong valves.

This is what the tops of the valves look like when you sit a LS3 valve on an LS7 seat.

If you know what your looking at you can see where the original valve sat. His response was that the valve was sucked up into the seat. Yeah a set of heads with less than 5,000 miles on them...LOL

Facts found that day and an expensive lesson learned. Intake valve guides were shot wrong valve stem seals. I'm just glad I caught it before anything got worse as it might have pushed me to the point that a certain somebody would not be breathing the air anymore.

 

The machine shop just cut the seats. I disassembled and reassembled.

 

Alright, to update this I did some further diagnostics. Either the Longacre leakdown tester I got is not sealing correctly on the spark plug seals or cylinder 3 bleeds down immediately.

• The spark plug for cylinder 3 is also covered in oil after cleaning and running for a few minutes
• Oil is clean so I doubt head gasket
• Coolant is clean so I further doubt head gasket
• Still burns oil with intake blocked off where PCV would pull in air
• PCV fixed orifice does not smoke or have any appreciable blow by as far as I can tell
• The valve cover baffles look clean
• As far as I can tell the fixed orifice (PCV) in the valve cover is not replaceable
• The valve actuate normally and nothing looks amiss in the valvetrain
• No air comes flying past the valve guide into the valve cover

 

Use the leakdown tester ,, put about 50 lbs in the cylinder, if you hear air coming out of the oil filler you have found your problem, piston/ring seal bad..

Only two common ways to drop pressure hard on leak-down, valve problem, or ring/piston problem, if its valves you'll hear air out of the intake or exhaust, oil filler its a piston issue.

Good luck!

 

Is that No.1 intake rocker arm that looks to have burnt oil on it and I'm wondering if the oil is leaking through the valve stem seal?

 

I was hoping it isn't rings based on clean oil and no air coming through the pcv orifice. But the oil filler cap is a good idea. Would the size of the hole on the orifice slow down airflow enough to not register blow by?

 

I will have to look harder at it. The intake rocker on cylinder 3 is darker than the rest. Not sure if I mixed and matched parts or if it got cooked when the lifter turned sideways and ground down the cam lobe. That is what necessitated the rebuild in the first place.

 

What I meant to say was that the No. 3 intake rocker arm as its valve stem seal could be the reason your getting oil like that and its leaking into the combustion chamber. Did you have the heads checked out, especially the valve guide for the No. 3 intake?

 

I replaced the valve stem seals. Did not replace the valve guides though. If the air comes hissing by there I will just opt for the cheapest AFR heads like I should have the first two around.

 

You wont get air thought the guides, but typically on the ones I've chased you'll see a lot of buildup on the stem right below the guide on the valve head if its blowing oil through.

 

I have never looked there,, I just learned the pull the oil cap and vent and listen method many years ago and just stuck to it.. LOL
I have seen where like 1 failed oil scraper ring raised hell with a cylinder as well as 1 bad injector washing the rings and cylinders down..
BTW I'm running the L59 33lb injectors as well on my L33. So far so good..

 

Ah. Good point. The valves will be sealed against the head at TDC.