Hey all,

I have my intake off to do some modifications to it and found that the whole inside of the plenum was coated with oil. The excessive oil was so prevalent as to pool at the intake valve in #4 and #6. These two valves, you could see the oil pooled. I did not specifically check all the other cylinders but all the intake ports "seemed" equally coated with oil. It did not necesarily seem to be coming from the valve guides.

Another perception I have had is excessivly dark oil after only 50 miles of driving. Granted it is 90% road racing but still, to be so dark so soon seems odd.

I have about 500 miles on this engine as an FYI. Almost all done in racing conditions and a dyno break-in of the rings before given to me. However, I did have to spend an hour or so at idle tuning this engine before I could get it on the road for WOT runs.

Can someone give me some direction on where to go? First, I don't fully understand our LT1 intake manifolds and would like to see where this oil would be coming from. Second, I would like to understand what could be causing this (excessive pressure?) in the engine.

FYI, the engine runs phenomenally well otherwise and seems to make power where it is supposed to however, I have not had it to a chassis dyno as of yet. Currently, I have the rev limiter at 6300 RPM and bounce off of it regularly at the track.

Thanks all,
Ben

 

Do you have any evidence of oil builup under the top cover of the throttle body, and in the rubber hose that runs from the throttle body to the passenger side valve cover? Any oil on or right behind the throttle blades?

 

Thanks for the help!

Checked this after you wrote. TB is dry. The top of the TB, under the cover, is also dry.

Further, I did an inspection with a probe at each intake valve and found oil sitting on #4, #6 and #3. The rest seemed to have some indication of oil but not enough to register on the probe.

Inspected the plenum and see what seems to be more oil as you go farther back. Drier up front and wetter towards the back.

Could this be a faulty PCV valve?

 

PCV valve causes problem in the crankcase, and a backflow of oil mist through the hose to the throttle body. That doesn't seem to be the case, if you don't have any evidence of that happening. Are you sure your intake manifold gaskets are not leaking.

 

Fred,

I went out and looked at the old gaskets. They were "wet", oily, on the bottom part all the way through (looking at it from crankcase to intake). It was more prevalent on some cylinders than other but sadly, I don't know which way they originally went on as they are now off. However, I could see an indentation of both the intake and head in the gasket. I am not an expert, but my feeling is there was sufficient sealing.

Just to look at all reasons for an oily gasket, could this not be from the oil settling in as it come from the intake and flowing down by gravity?

If it is a gasket leak, do I have enough reversion going on that it could push the oil back up into the plenum to coat the inside of the intake?

Looking at the force of reversion, could it be that I in fact do have a valve seal problem and the reversion is pushing some of the oil back up into the plenum and coating the intake?

 

Your static compression along with dcr looks to be close to mine. My heads have been milled along with my block being decked .015. I had to have the intake milled to seal correctly. Was this done to your intake?
Some people will slot the intake holes to fit but that doesn't fix the problem of the intake not sealing.

 

That was one of the reasons for pulling the intake. I wanted more smooth flow and knew decking the block without machining the intake was leading to an inperfect fit. However, I would have never thought that the heads/intake being off by 1/8" or so would impact the sealing between the two.

You have had this problem in the past when you did not mill the intake? Further, is the reversion that strong that it throws oil back up into the plenum?

 

With my LE ported intake, I had this problem. I didn't have large amounts of oil pooling, it was leaking slightly and enough that I would loose 1/2 quart between oil changes. I went with AI this time and they machined the intake to correct the geometry. Every bolt fit perfect, un like the LE intake. I don't think Lloyd did any machine work to correct the angle.
Another possible location for oil could be the studs.Did you use any sealant or thread locker on the studs. I don't go into the motor enough to remember which studs actually go into the ports but I do know that a few are open to the ports.

 

I assume you mean rocker studs?

No sealant was used with them but I think I remember that all the AFR 190 rocker thread holes were blind. Can't remember for sure.

Thanks for giving me directions to think about this issue. Intake now at machine shop...

 

Correct, I meant the rocker studs. I didn't read or realize that the AFR190's were blind. Good to know.

What intake gaskets did you use?

On a side note. You were talking about pressure building up, try this one. I had a rental car from Montreal for work about 2 months ago. I made it about 25 miles south into Ontario and all of a sudden I hear a loud bang. I look in the mirror and I see this black thing bouncing down the road. I assume it was a piece of asphalt. I pull over and can smell fluid. The piece of asphalt was the oil fillercap/neck. It blew off the plastic valve cover where it should have been molded/welded and must have puked about 2 quarts of oil everywhere. Never seen anything like that before, but it was a Chrysler

 

Used Fel Pro 1284. These are paper covered steel core but have a blue ring around each intake for additional sealing (I assume).

Planning on using: Fel Pro 95580. These are graphite covered steel.

You have an opinion on either one of them?

 

I am using the 1284. Never had a problem with them except for the intake not sealing. Are the graphite ones a little thicker?
I am currently using a graphite insert on my Earl header gaskets: http://store.summitracing.com/partde...A3BERL&FROM=MG They are finally the first gasket I have used that don't leak and the inserts are replaceable. They seal nice so maybe you will have better luck with the graphite gaskets.

 

No. The graphite ones are actually thinner by about 0.010 - 0.007 in.