I got a junkyard EZ36D (Subaru flat 6) from a junkyard to go in my rallycross car. When I get the motor I do a leakdown and find the exhaust valves leak. One cylinder has 70% leakdown. I pull the heads and lap them excessively, but they continue to leak acetone on the bench.
The valve faces appear to have little pits on the mating surface. The rest of the engine looks great (as it should being out of a 2011), so I send the heads off for a port and valve job.
When I get the heads back I notice they still leak acetone. Not only did acetone get by, but light did too. I call the shop up, and the employee I talked to (who did the port work; the machine work was outsourced) seemed genuinely baffled. They give me some shipping labels to send the heads back.
A week later I get an email:
This seemed like BS to me, so once I got the heads back I take them to a local machine shop that does a lot of Subaru work (I did not use them originally because they aren't very reputable). They tell me the valve seats were probably cut with a carbide bit which chattered a bit, leaving high areas on the seat. They lap them and tell me they now seal. I take the heads home and they still leak acetone, but not nearly as much as they had in the past.We have a few issues, we have never "tested" a valve job by a flashlight method, We do 5-10 sets of heads a week for 10 years and have never used this technique. This is not the industry standard. They are done via a vacuum test on the ports. We asked multiple head shops in the area including our own and confirm the same. the valves will seat in quickly regardless of light . We then tested several other sets here and we get the same results. If you hand lapped the valves this would get rid of the light you can see. We and most shops don't offer that service.
The standard is 20-25 inHg, yours tested at 21-23" both with valves that do and do not have light showing.
So am I just crazy for testing valves with acetone? I've never had known good heads leak before.
Thanks for any help.