I think lapping valves using one of those suction cup sticks is hard and there must be better ways.

So here is what I was thinking. I was thinking to get a really thin (medical or engine) hose that the valve stem will fit into as a male into a female and the hose will hold it tight. On the other side, I would stick a drill bit (that is on a drill) that is the same or similar size as the valve stem into the hose just like I did the valve. The hose should be as short as possible for accuracy and the only reason to use it because the drill mandrel will not reach the end of the valve. Then you spin the valve using the drill and hose rather than manually.

Can you verify if this idea is feasible and will not damage anything?

  • 1
    Don't take short cuts ... that's what got you to need to lap the valves in the first place. Jul 13, 2015 at 15:56
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    The drill won't spin it in more than one direction. You won't get much force on the face of the valve this way either. I prefer to do them by hand as you can get a good feel for how well the job is going. Jul 13, 2015 at 16:04
  • you can spin some in one direction and then switch to the other. not the same frequency as doing it by hand
    – amphibient
    Jul 13, 2015 at 16:07
  • 1
    This guy does an excellent job in this video. I wouldn't do it any other way. As @SteveMatthews says, it's the best way to feel what's going on. Using a drill is going to cause issues. I see some nut job has put the method you are suggesting on YouTube ... I wouldn't touch it with a 10' pole, no matter how long he says he's been wrenching. Jul 13, 2015 at 16:16

2 Answers 2


Attempting to do this will very likely damage the valve seat, valve itself and potentially the valve guide. Lapping is about finely honing the seat and face together. Power tools at this stage and in this method will introduce greater chances for error.

There is a better way than lapping valves by hand, it's call doing a valve job. You recut the seats, and resurface the face of the valve. Properly done with precision machine tools you will not need to lap them to get a proper seat, or only minimal lapping. There are many tools and attachments for doing valve jobs.

If doing a hand lap is very hard it could be that the valves or seats are damaged to the point where that's not the correct fix.

  • is valve seat the ring at the end of the shaft (part of cylinder heads) or is it the part of the actual valve that touches that ring ? I'm just inquiring about terminology
    – amphibient
    Jul 13, 2015 at 16:58
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    The valve seat is the ring that is part of the cylinder head. It is commonly a hardened steel pressed in to the head. The valve face is the part of the valve that touches that ring.
    – elmerfud
    Jul 13, 2015 at 17:12
  • thanks. what do you call the flat part of the valve that faces inside the combustion chamber ?
    – amphibient
    Jul 13, 2015 at 17:13
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    I've always heard of it referred to as the valve head. Here is a picture showing the parts of a common engine valve. biosystems.okstate.edu/home/fharry/3211/900_Homework/…
    – elmerfud
    Jul 13, 2015 at 17:38
  • Even when you do a valve job, you should always lap your valves. Doing so will ensure they seat and seal properly. Jul 13, 2015 at 18:27

I use without any issues a reversible screwdriver battery drill in its slowest speed, some turns one direction, then stop, up and down "tap" against the seat and more turns the other direction. These power screwdrivers are quite slow in the minimum speed, probably slower than hand lapping.

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