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if i'm getting new valves for my 1920 Briscoe b4 34 motor . would you ship it off to a shop to have them valve ground or would you use lapping paste (i think that is the name of the paste. the sandy paste) it is $25 a hole . getting it to the shop is going to be a hard.

what would the best way to have it in a truck ?

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Posted (edited)

I can’t speak about your specific model of truck. I can tell you that I hand cut valve seats with special vintage tooling and abrasive pads. My exhaust valves were hardened. It can be done. Engine was in the car.  It depends how bad your seats look. I’ve seen some seats in very poor condition after sitting in a field for decades. Those seat examples should be dressed with stones and powered tooling.  

After seat grinding by hand, I lapped in all new valves with the sandy lapping compound. I got good results. I spent a week of evenings leaning over the big bulbous fenders. It worked, but took time and effort. 

The car was a 1953 Chrysler. Flathead 6 engine. 

Edited by keithb7 (see edit history)
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Posted (edited)

There should be an auto machine shop near you that can do the job. I know there are not as many around as there used to be. Are there any vintage car guys, or racers in your area? They usually have valve grinding gear or know someone who does. There are a couple of local garages that run stock cars, they have engine rebuild equipment but they don't advertise it, they just use it on their own engines, but will do the job if you ask.

You need to check the valve guides and replace, knurl or resleeve them as necessary then grind the valve seats.It may be necessary to open out the seat to get the valve seat the right width.  The finishing touch is to hand lap the valves with the finest grinding compound.

Hand lapping will work for an overhaul but in your case you need the machine work.


Edited by Rusty_OToole (see edit history)
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If you can find someone with a valve grinder, the seat grinding equipment is very portable and can be brought to your engine. If you have new valves, then all that is required after the seats are done is a light lapping with some fine compound to just check the seat seal. Guys like me, and many others on here, have valve grinding equipment. You just have to find a close one. 

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Posted (edited)

For my first experience grinding valves - I had to fabricate new valves, valve guides and re-cut the seats by grinding and hand lap the valves in. Grinding the seats is not a difficult job - its just finding the equipment. In this case a very generous friend loaned me his valve seat grinder outfit which worked excellent. In my case I had to make a custom pilot to fit the guides. If your using one of these rigs make sure the stone is dressed often and go very, very lightly. It doesn't take much to over do it and a lot of material can be removed in a heart beat!


With that done I lapped in the valves by hand using fine lapping paste mixed with oil. Again... go gentle! Let the weight of the valve do the work and use layout dye on the valve to judge progress. Also after a few quick semi-circular (1/4 turn) swishes back and forth, lift and rotate it 1/4 turn and repeat until the layout dye on the seating surface of the valve indicates that you have a good shiny seat for about 3/4 the width of the surface.


Don't use too much paste. It will tend to squish out at the edges and leave too much in the middle of the seat and will concave the seating surfaces.

As others have said - if your valve guides are worn all this effort will be for not. With new guides installed you may be surprised how the valve seat actually shifts a bit or the old one is off kilter.


Here is the grinder and the tool for dressing the stones.




In this photo you can see the custom pilot. This allowed precise alignment of the seats both concentric and perpendicular to the axis of the guide.




Valve following hand lapping. These were bi-alloy stainless valves originally intended for a EMD locomotive. I had to cut to length, turn the head to diameter and machine the seat and the keeper.




New valve guides ready to press in




And a big old valve (2-5/8" dia.)  filling a big old hole




Valves all done!


Edited by Terry Harper (see edit history)
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