Slight oil accumulation in air bridge and air horn

[Don in VT]

Hi,

Well by now I have a little experience with the Plenum pull, lift or what ever and I hope that the last pull I did today (the 4th) will be the last for a while otherwise I will have to negotiate a volume quantity gasket price with Jerry.

Now on to my new observation. When I popped off the air bridge I noticed an accumulation of engine oil in the bottom of the air horn and air bridge where they meet. I have not noticed this before. I did a water pump and Samcos. I did not mess with any systems under the plenum except to reconnect all the secondaries vac lines. The reason I did the last pull was because I did not notice that a hard vac line was cracked so I had to go in again and fix just that.

The PVC valves are working and the lines are reasonably tight. All other lines to the air horn are tight.

Any ideas would be helpful.

Cheers,

Don

[VetteMed]

The cam cover breather tubes are the most likely culprit, I would think, being that the vapor they carry enters into the intake tract right at the junction of the air horn to throttle body. Maybe deteriorated packing material in the recess of the cam cover, no longer trapping oil droplets?

[GOLDCYLON]

Originally Posted by VetteMed

The cam cover breather tubes are the most likely culprit, I would think, being that the vapor they carry enters into the intake tract right at the junction of the air horn to throttle body. Maybe deteriorated packing material in the recess of the cam cover, no longer trapping oil droplets?

Concur you need new foamy sponge squares. Also a catch can might be a future consideration. GC

[tf95ZR1]

I asked Marc H this question. He said a teaspoon amount
is normal. Maybe he was joking, but he said finding no oil
would be a problem.

I found this and hope posting this response is OK with Marc:

"A cc or two of oil pooled in the air duct and a wet air horn are normal for the LT5. Some engines have less of it than your engine, you are on the high end of the normal range. There is more oil when the engine is run hard. That's good for you and the engine. I feel sorry for guys with dry air ducts."

My guess is the last statement does not include those with oil catch cans.

[Don in VT]

Hi,

Thanks for all the responses. I do have one question on the "normal" oil accumulation at the air horn/air bridge area. One aspect of the comment from Mark H that I should understand is the time element. How long should it take to accumulate 2 cc's of oil. My accumulation occurred over a couple of days of driving and about 100 miles of driving. Seems high to me.

I fully understand oil back-streaming in a partial vacuum but this oil is on the atmosphere side of the TB. The air stream is going "from" the air horn area so where did the oil come from ?

Cheers,

Don

[GOLDCYLON]

Originally Posted by Don in VT

Hi,

Thanks for all the responses. I do have one question on the "normal" oil accumulation at the air horn/air bridge area. One aspect of the comment from Mark H that I should understand is the time element. How long should it take to accumulate 2 cc's of oil. My accumulation occurred over a couple of days of driving and about 100 miles of driving. Seems high to me.

I fully understand oil back-streaming in a partial vacuum but this oil is on the atmosphere side of the TB. The air stream is going "from" the air horn area so where did the oil come from ?

Cheers,

Don

Don, Andrew correctly answered this question

[GOLDCYLON]

Originally Posted by tf95ZR1

I asked Marc H this question. He said a teaspoon amount
is normal. Maybe he was joking, but he said finding no oil
would be a problem.

I found this and hope posting this response is OK with Marc:

"A cc or two of oil pooled in the air duct and a wet air horn are normal for the LT5. Some engines have less of it than your engine, you are on the high end of the normal range. There is more oil when the engine is run hard. That's good for you and the engine. I feel sorry for guys with dry air ducts."

My guess is the last statement does not include those with oil catch cans.

Hes right oil in the plenum is also normally found. A lot of members have installed oil catch cans to captue excess oil.

[Don in VT]

Hi All,

Wow, never to old to learn something new. My thinking was that
the filtered air in the air horn is drawn into the cam cover and on through the motor and finally exiting at the PCV valves and on into the motor. I can now visualize that, under certain circumstances, the air flow over the inlet air horn hose fittings may have a venture effect and actually draw the air oil mix that is present in the cam covers. It is also possible that under certain engine conditions the vacuum drops off and the cam covers could go slightly positive with respect to the Air Horn and oil will migrate to the AH.

Anyway !!

I am not going to pull the cam covers at this time but instead come up with another solution to solve the over oiling of the Air Horn.

BTW, the ZR is all buttoned up now and passed its first smoke test and it is running great. I had O problems when filling the cooling system. The Samco hoses look great. The new thermostat controls well, The water pump is smooth and quiet. THE SECONDARIES ARE WORKING !!


Thanks to you all for all the help and support,

Don

[scottfab]

Two things I know will contribute to the amount of oil accumulation.
1. thicker than 10w30 oil.
2. overfilled oil.

[Don in VT]

Hi Scottfab,

Thanks for the heads up on the oil viscosity and level. The oil level is spot on in the center of the hash marks and the oil is Mobile 1 10w/30.

Again, I appreciate the heads up

Don