I am interested in getting some input on next steps in diagnosing oil consumption of my engine.
I rebuilt my lt1 the winter of 2019/2020. Last year I put 4k miles on it. This year I have put 1k miles on. Engine started out as an LT1 with ~140k. I had been collecting parts to do LE2 HCI with a 227/235 LE cam. I ended up also doing a forged 383 (see signature) with a deck height of 9.015 and rings gapped for nitrous. Engine runs great, has nice drivability, and pulls hard to 7k, and so far has done 12.65@115 with a 2.09 60ft on street tires.
Here is a list of things I have done to diagnose and try to solve my oil consumption:
The potential causes and fixes I see are:
I rebuilt my lt1 the winter of 2019/2020. Last year I put 4k miles on it. This year I have put 1k miles on. Engine started out as an LT1 with ~140k. I had been collecting parts to do LE2 HCI with a 227/235 LE cam. I ended up also doing a forged 383 (see signature) with a deck height of 9.015 and rings gapped for nitrous. Engine runs great, has nice drivability, and pulls hard to 7k, and so far has done 12.65@115 with a 2.09 60ft on street tires.
Here is a list of things I have done to diagnose and try to solve my oil consumption:
- Initially noticed some oil consumption and blue cloud on startup. Checked for external leaks. Even today, the engine has no external leaks. Found oil in throttle body, intake, and cylinder intake ports, and spark plugs. Observed big blue smoke cloud on start up after around 2-250 miles on the engine. This got progressively worse for 100 miles before plateauing.
- Compression test, dry, warm engine (psi): #1 [210] #2 [209] #3 [217] #4 [205] #5 [218] #6 [215] #7 [214] #8 [220]
- Installed a new valve cover baffle elbow between the passenger valve cover and the throttle body. No measurable improvement - oil still found in throttle body and intake, blue cloud on start up still exists.
- Installed a Mike Norris PCV catch can set up between the PCV valve (fixed orifice design) and the intake. The catch can only caught perhaps 2/5 cup of oil in 3k miles. no measurable improvement.
- Drove car for a bit, noticed spark plugs have oil on threads and carbon buildup. Engine consumes 1 quart of oil every ~200 miles.
- Inspected and replaced the valve seals fall of 2020. The valve seals I removed looked fine, but installed new ones anyway. Valve stems had a bit more play in the valve guide than when the heads were off during initial motor assembly - valve stems/guides were very tight and I did lubricate the stems and guides prior to installing the springs. No measurable improvement, still have plugs getting coated in oil and blue smoke on startup.
- Removed intake and replaced intake gaskets. Observed that intake valley was likely bottoming out on block before intake ports could compress against cylinder heads fully. Removed material from intake valley and enlarged intake-to-cylinder head holes slightly to enable easier assembly. Its possible that the intake still requires milling of the intake port face to match the geometry of the heads. Some improvement (maybe?): engine seems to consume oil at a slightly slower pace (1 quart every ~300 miles) and blue smoke cloud on startup is less noticeable.
- Engine runs smoother after cleaning/replacing spark plugs, which makes sense since the spark plugs are still coming out oil on threads, some buildup of carbon. When I changed the plugs I also did a quick compression test, cold engine. dry, #1 [230] wet (WD-40 spray), #1 [230].
The potential causes and fixes I see are:
- Valve guides are worn/burnt up --> pull heads and have the valve guides replaced.
- Intake doesn't fit heads/block well --> pull intake and have the intake machined to match the heads and block better.
- Longer stroke has resulted in additional oil mist in engine --> install second catch can between passenger valve cover and throttle body.