Valve seat issues

Bobby DiDomenico · 07-06-2016, 08:31 AM

Have helped a friend with a few of their Flathead Straight-8 and V-12 engines. This one was rebuilt about 2 years ago and has cylinder pressure issues, to the point he removed the head and lapped the valves. It seems all the intake seats (and valves) lapped well. The exhaust seats seem to exhibit an hourglass shape. You can see the dark areas where the lapping compound is not reaching. Some of the exhaust valves had a noticeable cupping when you lay a straight edge against the seat. He said it was running hot but it is with a 1931 factory gauge. It did not use any water on a trip to Texas which was aborted in MO. where he checked compression and returned

I did not see how the shop did the valve job, so I don't know if the block or cutter were moved along. (While the cylinders come off the V-12, this engine must weigh over 800 pounds so I don't see them moving it around easily.) Any idea why the intakes don't exhibit the same issues? If it was cutter induced I'd have guessed all would show the same pattern. Any ideas?
I really, really, really, don't want to disassemble the car and remove this thing again. :-)

07-06-2016, 08:31 AM	#1
Bobby DiDomenico Senior Member Join Date: Jun 2002 Posts: 907 Likes: 85 Liked 88 Times in 45 Posts	Valve seat issues Have helped a friend with a few of their Flathead Straight-8 and V-12 engines. This one was rebuilt about 2 years ago and has cylinder pressure issues, to the point he removed the head and lapped the valves. It seems all the intake seats (and valves) lapped well. The exhaust seats seem to exhibit an hourglass shape. You can see the dark areas where the lapping compound is not reaching. Some of the exhaust valves had a noticeable cupping when you lay a straight edge against the seat. He said it was running hot but it is with a 1931 factory gauge. It did not use any water on a trip to Texas which was aborted in MO. where he checked compression and returned I did not see how the shop did the valve job, so I don't know if the block or cutter were moved along. (While the cylinders come off the V-12, this engine must weigh over 800 pounds so I don't see them moving it around easily.) Any idea why the intakes don't exhibit the same issues? If it was cutter induced I'd have guessed all would show the same pattern. Any ideas? I really, really, really, don't want to disassemble the car and remove this thing again. :-) Attached Thumbnails Last edited by Bobby DiDomenico; 07-06-2016 at 08:34 AM.