Valve Seals, Leak-down Testing

[Brad Bartilson]

I bought some high flow used heads. In order to cleand them up I pulled the valve out. It felt bad coming out, seemed like small pieces of brass shavings came along with it. I replaced the seal, installed the heads. Have run for 5K miles struggling with oil loss and dirty oil. Compression checks good. Leak-down testing showed some cylinders up to 15%. Mechanic said this is in normal ranged, other references suggest anything above 8% indicates bad valve sealing. By installing a breather on the driver's side valve cover I eliminate excessive exhaust smoke. Questions-
Does leak-down testing indicate if the valve guide seals are bad? Is the 15% leak down indicative of bad sealing? Can the constantly dirty oil be because of a bad valve guide seal? Are the drivers and passenger side valve cover compartments essentially connected via the intake, see the same pressure?

thanx for any help,

Blowin Smoke in CO,

Brad87TR
bartilson@yahoo.com

 

[NC87GN]

15% typical.. Hmmm.. Do not agree with the mechanic on that.. 5% or less is great, 10% would be MAX. Did a leak down test, not to long on my set of ported heads, and seen a MAX of 8% on cylinder 3. Every other cylinder was near 4-6%. Keep in mind rings play an important role in leak down test. Just as a note make sure the valves are closed on that cylinder your testing. Every 120 degrees on the dampener with a firing order of 165432. HTH..

Mike Banas
87GN