hello,

I have just had my valve guides replaced and my machine shop said i needed to grind the valves and the seats, well the shop did that for me.

My question is do i need to "lap" the valves for the individual seats to match up?

Any input would be appreciated.

Brian

If the shop did an accurate job no lapping should be required. The modern way of doing valves is to cut a slightly different angle(~1/2 deg) between the valve and seat. This causes the intial contact to be a thin line which quickly broadens as the valves seat. You can do a quick check by marking the valve face with four marks with a magic marker spaced 90 deg apart. Drop the valve in the seat and manually bang the valve up and down. When you pull the valve out you should see that all the marks have been disrupted by the seat. I would also contact the shop and ask them what their standard practice is. When I last had a valve job all my valves had these marks so I know the shop checked them.

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Bill Reimels
Now down to one:
1972 300SE 3.5 W109 (Euro delivery)

I was taught years ago to always hand lap valves/seats even after doing a three angle valve job. I used a special blueing paint on the seats to determine whether the valve was making a full 360 degree contact with seat. If not, then I'd have to hand lap a little longer. I miss doing cylinder head work. It's the most satisfying part of an engine rebuild.

I hand lap (usually with a drill though). The only thing I hate about head work is the torque angle adjustment most engines now require. Setting up the torque angle guage on each bolt is aggravating, especially when the pattern calls for different angles in the sequence.

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85 300CD
83 300TD
78 240D (daughter)

I was taught (not long ago) to hand lap them after new guides & gringing then check them with the "blue" stuff then fill the head with solvent, let it sit for a while and see if any leaks out.

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1985 Euro 240D 5 spd 140K
1979 240D 5 spd, 40K on engine rebuild
1994 Dodge/Cummins, 5 spd, 121K
1964 Allice Chalmers D15 tractor
2014 Kubota L3800 tractor
1964 VW bug

"Lifes too short to drive a boring car"