Oily residue in intake & throttle body

[91nsx85crx]

Looking for a liitle advice on why there is a black greasy residue in the throttle body on the intake manifold side of the throttle plate. let me add the following info: Crankcase gasses are vented to the atmosphere. The engine was built for turbo but is running N/A at the moment. Heads are ported with 1mm oversize valves. Block is Darton 95mm with JE 9:1 pistons. Ever since the rebuild (15,000 miles ago) there has been an oil consumption issue of 1qt. per 500 miles. The compression checks out fine cylinder to cylinder. Since the oil consumpsion issue was ongoing, I replaced all the valve seals, but nothing changed as far as residue or oil consumption. I hate to tear down and hone and re-ring and I'm not sure if the residue & the oil consumption are related.
Any thoughts or advice would be appreciated.

Thanks,
Todd

 

[C-speed]

I assume its turbocharged? It's a sign that oil is leaking past the compressor seal.

I'm sure if you checked inside the lowest intercooler pipe (closest to the ground), there will be a good collection of oil in there.

Check the compressor inlet too, there'll probably be oil on the surface of the housing.

There may or may not be excessive shaft play that you can feel by hand, but it's definitely leaking.

Time for a rebuild.

 

[91nsx85crx]

There is no Turbo at this point, if there were I would agree with your assessment. I have had that exact issue on another turbo'd car.

 

[C-speed]

There is no Turbo at this point, if there were I would agree with your assessment. I have had that exact issue on another turbo'd car.

Oops, should have read your first post more carefully hehe

Sounds like that valve stem seals to me. I know you said you replaced them, but oil in the intake manifold can only come from one place since you stated you are venting the crank case pressure to atmosphere.

Once good way to check if blow by is coming from the rings or the valve stem seals is to do these 3 tests:

1) Run the car up to redline in like 2nd gear, left off the throttle and let the rpms come down while still in gear. Watch the rear view mirror or have someone follow you. If smoke (blue) comes out of the tail pipes, then you have bad valve stem seals

2) If, while you are flooring it up to redline, it is smoking (blue) from the tail pipes, then you have bad oil rings.

3) Drive the car around until warm. Park the car for a few hours or over night. When you start up the car, if it smokes (blue) out of the tail pipe for a few seconds or more right after startup, then the smoking goes away, then you have bad valve stem seals.


side note: if it smokes under BOTH conditions (1 and 2), then you have both bad valve stem seals AND oil rings

A compression and/or leak down won't tell you the condition of your oil rings or valve stem seals.