Grinding Valve Seats

Unknown

I had low compression in two cylinders, so I took the head off the '38 Terraplane to check on the condition of the valves. Found three of the six exhaust valves with seats that won't smooth out with the normal lapping compound. Is grinding the seats something I can do myself, or is it best left to the "experts"? If it is something I can do, is there special equipment needed, or can I get the appropriate grinding stone and chuck it into an electric drill? Where can one get the stones?



Thanks for any assistance you can give me.



Paul Caldwell

Unknown

We were fortunate to pick up a valve and seat grinder at auction and have seen several of these in the past year. For the seats you need the driver, the head with the stone ground to the proper angle(s), and a guide that fits without a lot of clearance thru your valve guide. It does the job rather quickly and with a very nice finish and ready to lap. Depending on your location you may want to watch out for an old auto repair garage or farm auction. With the proper stones, holder, and guide I would guess you could do it with a drill. I think I used two different size stones and guides on the last one I did. It's not a hard job to do at home and beats taking the block or the car to the shop to have it done if thats all it needs. I think I have about $75 in the whole thing including the stone dressing attachment.



I wouldn't try it with just a stone and not a guide!

Geoff

Most machine shops today use special stones and guides, and don't lap valves in any more, using a technique called "synchro seating". However for the home workshop there are ways around the problem. You will need to improvise a little, and get some basic gear. I have re-cut valve seats by using an old valve with a slot in the head, lots of coarse paste and a dash of kerosene, and a made-up driver in the electric drill on the head of the valve. This breaks the hardening and glaze on the seat, and also semi-destroys the old valve face, but it did the job. Finish off with fine paste and then lap the valve in. Crude but effective. I also have an old-fashioned steel valve seat cutting set, but if you try and use these on a work-hardened and carboned seat you will soon dull the cutting edge, so it's best to break the surface by the afore-mentioned method. If you can't find an old valve with a slot you can use a conventionl valve lapping suction tool, but you won't be able to put as much pressure on the valve, and it will take longer. There is a danger of cuting grooves in the seat, so do be careful. Small grooves don't matter a lot, and the valve will seal okay. However, if you don't want to risk any of this, you should be able get someone to do the seats for you. The equipment is quite portable. good luck,

Geoff.

Hudsy Wudsy

It seems that I'm forever coming accross old valve gringing outfits on ebay. Many contain the stones, driver, and guides in an old wooden box. Read the listings carefully as a number of them are just for Fords.

Uncle Josh

I just had all the seats and valves in my 308 ground and vacuum tested at a machine shop. They charged me $85 plus tax and it's done right.



Motor is out of the car of course.