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Cutting Valve Seats

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  • Cutting Valve Seats

    I have been fiddling with Home Shop Engine machining for my Bike Engines. Now i been doing research on seat cutting grinding. I hear from the Old Boys that the Serdis dont work well at all and also the Newall seat cutters leave chatter and concentricity is a issue along with some damage to the Valve gi\uide itself. I am wondering from the pros ?> which is the way to go? Grind with sioux style stone s ana mandrel? or ?? I have a boring bar new table made up now and am getting a honing tank planned for my engine projects. Im low budget so a used 34000 dollar seat valve machine doesnt enter the Picture. Than mike

  • #2
    Soux works, use three different angle stones to leave 1/16" land centered on the valve face. Peter
    The difficult done right away. the impossible takes a little time.


    • #3
      I really can't tell you which is the best, cutters or grinders, but I always got a better finish with the grind stones. I used a Newall cutter set when I had a small engine shop and it did ok but I sometimes lapped the valve in, well, most the time I lapped the valve in. You can't do that on a multi angle grind or cut though.

      To be honest I still prefer the stones. I guess it's just what blows your dress up is what you'll use.
      It's only ink and paper


      • #4
        ok look at it this way. say you are building something that has to be real close. do you just use an end mill or do you grind it ? now that is why i gring valve seats. i have the indicator that checks the seats i have checked some that were done with cutters they were not even close to factory spect.


        • #5
          I'll second the stones - even thou the stone grinding systems are more expensive and require more maintanence to be accurate.

          I have a Van Norman Seat Grinder and a KwikWay Valve grinder. The Dresser pilot became worn and had to be replaced to get an accurate dress. Had to replace some Precision Ball Bearings in the valve chuck to bring it back into spec as well.

          Also occasionally I take a valve out of an engine that has never been opened before and find a non-concentric valve face maybe .002-.003 tro. Of course by then it has trashed the piston side of the guide as well.

          Personally I lap my valves in even with tripple cut seats. First 800 then 1200 grit paste. Don't bother buying 1 of those fancy "Egg Beater" style Lapping Drivers. Just take 1 of the cheap wooden ones, cut it in half, and turn down a shank on a lathe you can fit in a battery drill.

          Nice to have a presure test set up - they are easy enough to make. Also a Flow Bench - but they are a little more difficult to fab up, even more difficult to find, and require quite a lot more expertise to obtain verifiable results. How ever you'll also need a means to preheat to perform those 2 task

          Good Luck


          • #6
            I've used both. Both can do a fine job and both can do a botched job. The Neway system uses carbides so hardened seats are no problem. We caution our students (Community College Heads machining course) that when using the Neway, 1) use uniform pressure with each hand, and 2), lighten the pressure just before stopping the cutter. This reduces or eliminates chatter. We also do a quick lapping so we can clearly see seat area and if it is uniform.

            Stones can do an excellent job, but you need a specific type if you are doing hardened seats. Check Goodson's site/catalog. They also put a small cloud of grit into the air every time you true or cut.

            Off-center seats? No problem, you replace the guides, then do the valves.



            • #7
              Grinding valve seats is fine we always dressed the stone on the valve refacer to get the angle the same as the valve then smeared a light coating of bearing blue on the valve face to check if it was seating all the way round on the valve seat. If you have unworn valve guides and a good pilot and using a light weight air drill to drive the stone carrier you can cut a more concentric seat than you can with a Serdi. I never had much luck using Neway cutters. You can use old hand valve seat cutters to "crown & throat" the valve seats.
              Although we did sometimes lap valves it wasn't recommended. The thinking of the time was that due to the different heat expansion rates the grooves worn in while lapping would no longer match and the valve would no longer seat.
              This was standard practice in most Australian Engine shops 1950's to 1980's



              • #8

                Here is some good reading if you have time.


                • #9
                  Neway cutters work great

                  I have used Neway cutters with no problems. Cleaner than any grinder will ever be. Might have to make an arbor for your application, but if you are into any type of machining they are simple to make.


                  • #10
                    I always preferred to grind them. I never saw a need to lap if a proper job of grinding was done, although you can lap if you like.


                    • #11
                      Remember that the quality of a valve/seat interface is highly dependent on the state of the valve guide and stem.

                      Serdi seat cutting machines work very well if opperated properly. The head is mounted on a carriage that can be floated on air and the cutting head also has a large diameter balljoint that is air floated. The combination of the two should ensure that the cutter head is both concentric and normal to the seat before being locked down for the cut. Some head shops seem to rely on the machine to do a good job and let an untrained/unskilled person do the work.

                      It's quite difficult with the Neway cutters not to push the seat off centre and the guide/power head is a good idea.

                      The seat grinders are pretty good, but you can't do the small seats on many motorcycles or 4 valve car heads. The sheer weight of the grinder can make it difficult to stay in line.

                      I've got a single point cutter from T&S Machines. It's similar to the Serdi tooling.

                      Carbide pilots are much stiffer than steel.

                      If the seats are propperly cut, then you don't need to grind them in. They're not ground in at the factory and I don't know of any performance engine builder who does. Grinding just damages seat geometry. I use Prussian blue to check seat contact.
                      Paul Compton


                      • #12
                        I use both stones and cutters. Lapping is a waste of time and serves no purpose thanks to thermal expansion of the seat and valve. Lapping does look impressive when customers first see the finished product.
                        Non, je ne regrette rien.


                        • #13
                          Neways can be troublesome and time consuming to use, having been in the buisness for a couple of decades, I have found the easiest way to do a valve job is to pay some one else.

                          Or, a set of Sioux stones.
                          "the ocean is the ultimate solution"


                          • #14

                            Around here youre better off doing youre own rather than pay a Speed ??? Shop and get seats back that have run out like .003 or so. Been there done that and ill do it my self thank you very much. I just wonder which is the most efficient and proper way to cut seats, I am removing seats offseting the guides mreplacing seats and generally modding my heads a lot. Having everything in house makes it easier. Or maybe Turbo it then Heads dont matter do they?? If it doesnt go fast enough just turn up the boost, Simple isnt it? PS I liked youre turbo headers Steve Looked nice did you use 321 ss??


                            • #15
                              I use 304 from Burns, purged. If it was a street application I would most likely use the 321 but in a highly maintained race track environment the 304 has never presented itself as a problem.

                              I send my heads to Vance and Hines.
                              "the ocean is the ultimate solution"