What's the best way, without taking a head to a machine shop, to check if the valves leak? I have a couple of heads off of 617's that I suspect that some of the valves leak. After testing the compression on one when it was still on the block lead me to think that. After adding oil to the combustion chambers, no increase in compression was achieved on a couple of the cylinders.
I poured a little Marvel Mystery oil into all the intake and exhaust ports of the removed heads to see if any of the valves leak. There were a few that did indeed leak.
Am I going about it in the right way by doing this way or will valves leak any way by adding MM oil to them?

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DJ


84 300D Turbodiesel 190K with 4 speed manual sold in 03/2012