OK, its not a 409 but it has 470 cubic inches with a 5 inch bore and a 4 inch stroke so maybe it will be of general interest.
I'm doing my annual airworthiness inspection on mu 46 Navion and while doing the leakdown check found #4 cylinder hissing out the intake and only able to hold about 30 psi out of 80 at TDC. Video scoped the cylinder and found a good bit of lead deposits on the outboard edge of the valve and seat while the inboard side showed some heat staining from standing up next to the exhaust valve. No burn damage noted but stem was coked up some from lead as well. Not being able to get exited about pulling the cylinder, I decided to try lapping the valve in place. Put it on TDC and stuffed a length of nylon rope in the top spark plug hole until it backed up the intake valve then removed the rocker arm, put the spring compressor on and pulled the springs. Pulled the rope out and backed off the piston from the valve about an inch and pushed the valve in to where I could get a pipe cleaner with some lapping compound on the face, connected some vinyl tubing over the stem head and safety wired it in the keeper groove then started spinning away. After a while It felt pretty smooth and appeared to be seated thru the scope so I cleaned it up, put the upper plug in and the compression guage air on the bottom and gave it 80 psi on TDC and it came up to 65+ but still a little hissing from the intake so more work is needed. I'll do some more lapping tomorrow. Meanwhile DI tested the springs and they are way below spec at installed height but still close to spec on open pressure. Have a new set of springs on order.
Did I mention I hate pulling cylinders?
I'm doing my annual airworthiness inspection on mu 46 Navion and while doing the leakdown check found #4 cylinder hissing out the intake and only able to hold about 30 psi out of 80 at TDC. Video scoped the cylinder and found a good bit of lead deposits on the outboard edge of the valve and seat while the inboard side showed some heat staining from standing up next to the exhaust valve. No burn damage noted but stem was coked up some from lead as well. Not being able to get exited about pulling the cylinder, I decided to try lapping the valve in place. Put it on TDC and stuffed a length of nylon rope in the top spark plug hole until it backed up the intake valve then removed the rocker arm, put the spring compressor on and pulled the springs. Pulled the rope out and backed off the piston from the valve about an inch and pushed the valve in to where I could get a pipe cleaner with some lapping compound on the face, connected some vinyl tubing over the stem head and safety wired it in the keeper groove then started spinning away. After a while It felt pretty smooth and appeared to be seated thru the scope so I cleaned it up, put the upper plug in and the compression guage air on the bottom and gave it 80 psi on TDC and it came up to 65+ but still a little hissing from the intake so more work is needed. I'll do some more lapping tomorrow. Meanwhile DI tested the springs and they are way below spec at installed height but still close to spec on open pressure. Have a new set of springs on order.
Did I mention I hate pulling cylinders?