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  • Modifying engine valves

    New to this so bare with me. A neighbor asked me about modifying the stem on a engine valve so that it would fit into a old John Deere tractor. The original keeper groove would need to be welded full and a new one cut so as to be about .3 inchs shorter. I told him that he should look for other options as while someone could do it, it was out of my league. So my question is, has any one made such modifications and if so, how did you do it. I assume that any welding done would ruin the heat treatment of the valve and even if I over came that hurdle, how on gods green earth do you put it in a lathe. Any thoughts would be appreciated.

  • #2
    Without seeing the valve train, I can't really understand why the higher groove would have to be welded up. What is bearing against it which requires the solid stem?

    Any you are correct, welding on valves is not good science. However, a JD turns so slowly, there isn't as much force involved as a Top Fuel dragster engine.

    thnx, jack vines

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    • #3
      Shim up the spring.........
      Opportunity knocks once, temptation leans on the doorbell.....

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      • #4
        or make a new keeper.
        Assuming the valve will fit into the train at the length it is. Seems strange that he has a valve which is correct in every way bar the keeper...

        Dave
        Just south of Sudspumpwater UK

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        • #5
          I have recut a valve in the lathe with a toolpost grinder and slitting disk off a surface grinder, should have been done on a cylyder grinder i reckon, wouldent weld it youll probably end up with valve stem failure as the heat treat would be ruined [or strechy valves!]
          mark

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          • #6
            I don't think its worth risking the munch factor when the valve head drops into the combustion chamber without an invitation. This is one of those; "how could such a little part have destroyed my entire engine block and head?"

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            • #7
              OP did not say which engine.. but if a GP, no worries about valve coming out, its a flathead side valve.

              The valve stems are large ~ 7/16.

              Cylinders are a separate part on JD's, so block is pretty safe...

              Max rpm is 900 to 1400 rpm depending on model. so valves open half that...

              Not all parts are available some times, so adapting is an option.

              JD's have rocker covers too, and a lot of spring shimming won't cut it.. rocker won't sit right on long stem...

              The valves also mount horizontally on older Deeres, so falling into cylinder would involve some strange tractor angles...

              Gum and varnish would likely keep stem from moving more than normal anyway...

              Even if valve sticks out ~2 inches, it will not hit piston. Very large piston to head clearance... and a straight shot back in, they are not angled..

              Engine will obviously be running wrong if it loses 1 of 2 cylinders, and allow time to shut down..

              Many of my ~500 to 750 rpm antique gas engines, use a simple hole through stem and cotter pin to retain spring.. On a tractor, I would put a proper keeper in tho...

              Another option, is to make a set of keepers and valve spring caps, with a deeper recess to allow a keeper groove to be ground in lower on stem than stock...

              Edit: Heat treatment not much of a problem on these old critters..
              I would not weld a new head on a stem, but just about anything else ought to work for a parade/show tractor.. Not many have to earn a living 40 hrs a week any more...
              Last edited by Bguns; 11-21-2009, 06:09 AM.

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              • #8
                I've reduced valve heads just with ordinary carbide, before finishing in a valve refacer or T&C grinder. Maybe if you don't absolutely need to fill in the original groove, it's just a simple turning excercise? Of course, valves are not all the same material or same treatment.

                Tim

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                • #9
                  Originally posted by RoyClemens
                  New to this so bare with me. A neighbor asked me about modifying the stem on a engine valve so that it would fit into a old John Deere tractor. The original keeper groove would need to be welded full and a new one cut so as to be about .3 inchs shorter. I told him that he should look for other options as while someone could do it, it was out of my league. So my question is, has any one made such modifications and if so, how did you do it. I assume that any welding done would ruin the heat treatment of the valve and even if I over came that hurdle, how on gods green earth do you put it in a lathe. Any thoughts would be appreciated.
                  OK taking this for what's it's needed for why weld the groove and re machine it 0.300" is a fair way down so just cut a new groove and leave the old one.
                  Chances are you will need to shorten the valve ?
                  If you don't have to modify the length fit a 0.3" packer under the spring.

                  Modifying valves is something that done all the time. The Gardner diesel engine started life with 3/8" stem valves, as it got improved it still kept the same design so they improved the valves with the latest exhaust valves being made of Nimonic 90.
                  They were long valves with a threaded end for the cap to fit and a cross pin to hold it all in place.

                  By chopping this off and machining a new groove in it [ use a female revolving centre ] and a tad of work on the head OD, these dropped straight into 500 Manx Nortons.
                  I have done loads that have spent their whole working life round the Isle of Man circuit at flat out racing speeds and many other circuits without popping heads off etc.

                  .
                  .

                  Sir John , Earl of Bligeport & Sudspumpwater. MBE [ Motor Bike Engineer ] Nottingham England.



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                  • #10
                    Thank you for all of your responses. As to why the groove can not be simply recut you must understand that the "groove" is about 5/8 of an inch wide. While I do not no for sure I suspect that this is a pulling tractor and if so any thing has went. I like the idea of the custom spring caps though.

                    Thanks Again

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