Pics of my intake manifolds, what the hell is this oily crap?

[cpom]

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This is from a junkyard 2002 L36 with supposedly under 50K miles. What is this crap from? only 2 out of 6 intake runners are clean. Is this from driving with a bad EGR system? The contamination begins just after the throttle body plate as you can see in the last pic.

[97rs4life]

looks like common buildup. When I took off my throttlebody to port and polish it, the back was identical to that. It was filthy! Nothing a good cleaning can't fix though

[WickEdSix9838]

Its carbon and oil. All of them are like that.

[slow6]

get throttle body cleaner/spray
will take that right off


or p&p it

[cpom]

This is, what, from crap blowing back in before the intake valve closes? Or stuff forcing it's way past the valve? I am just confused how the intake side of the engine can buildup so much crap.

[geocor]

If its oily its comming from blow-by from the PCV valve.Crankcase gasses mixed with mists of oil get into your intake,normal unless excessive.At the C5 forum a lot of people there notice quite a bit of oil accumulation in their intake runners.They deal with it there by a PCV Catch Oil Can; or filtering the pcv hose with a simple Fram G-3 fuel filter,like I did,with my C-5.Don't know how we could get either set up in our V6's,due to the way the PCV is set inside the plenum?If you could find out how it would eliminate a great deal if not all oily residue,but not the carbon.

[AZ3.8Camaro]

A good polish job will prevent that from returning.

[cpom]

Now I heard the surface bumps and roughness present on intake pieces as they leave the mold and the factory was put there on purpose. This would be to create a more turbulent flow and mix the air and gas better for atomization. The whole polishing practice seems to go against that by making nice smooth runners. Can anyone comment on this apparrent contradiction?

Also, I am dropping this engine into a 4x4 truck which will ride on 35s, i.e. will rarely see high rpm action. the engine will spend most of its time between 1000-3500 rpm when I go offroading. Would the effort of porting and polishing the intake runners have any good low rpm results besides keeping them clean?

Eventually I was going to look at low rpm torque upgrades for this motor but I think stroking it is my only option. All the valvetrain stuff is good for racing.

[AZ3.8Camaro]

Its a crock.
Carbed the bumps will trap fuel puddles in the intake.
Fuel injected, you just plain want airflow. The injector, coupled with fuel pressure will atomize the fuel.