No announcement yet.

Engine valve advice needed

  • Filter
  • Time
  • Show
Clear All
new posts

  • Engine valve advice needed

    Okay,I'm getting things lined up to start in on my Fairbanks engine restoration.

    The engine needs valves,the head has soft seats of course,the valves are two different lengths,one is about 8" long and the other is about 6"with a threaded shank.

    The machine work is simple enough,but from what I have read the replacement valves are of a two piece design,the stem is steel and the head/seat is cast iron.

    Question is,should I use regular cast,or should I use ductile?The other unknown is the alloy and hardness of the stem material.
    I just need one more tool,just one!

  • #2
    F-M restoration? Engine details, please?

    Neil Peters
    Neil Peters

    When on the hunt, a broken part is better than no part at all.


    • #3
      Hi wierd,
      Most guys I know are using replacement automobile engine valves, as long as the head dia. matches and the stem is long enough. They cut the stem to the length they need. When the engine was built would probably coincide with the materials used. If I were making a 2pc. replacement valve I would use regular cast iron for the head and drill rod for the stem, then temper the tip that the rocker arm hits.

      Are they flat or angle seat valves?

      Hope this helps,


      • #4
        What year is the engine?
        Those "old" two-part valves were cast on the stem then machined. Modified valve springs can break the heads off. The old valve springs were very weak compared to today's sandards. The stem material was fairly soft tool steel. W-1 Drill rod, or similar, would be about the eqivalent.

        I'd go with modern valves. The seats are a toss-up depending on condition. Cast iron seats work well in these old engines. You can get them pre-cast in many sizes.


        • #5
          The engine is a Fairbanks 7-1/2hp "Z" with the Fairbanks "R" mag.Its old,but I have every single part including the crank throw cover and original fuel tank(insert envy here)I'm going to have the cylinder sleeved,its too pitted to work,piston and rod as well as all bearings are perfect,still tracking down parts and pieces for things like the mag.The one big part that I'll have to fabricate is the mag braket,darn things are always broke when you find them just like mine.Never will understand why when they used all that iron did they decide to use the cheapest pot metal they could find for the bracket.

          Valve stems,I as thinking of using nitro bar for the stems and doing a good shrink fit on the big ends.The guide hole will have to get reamed and bushed too which brings up another question,just how do the valve stems get lube?

          Oh,BTW, it does have angle seats.

          I just need one more tool,just one!


          • #6
            Valve stems usually get lubed by oil mist spashed up by the slinger.

            I don't think a press fit will work. Remember, that valve head is getting heated to about 1100F and the stem will rarely get above 300. Also, the valve springs are always trying to hammer the valve head off. Your call though.

            Would be a shame to hear a valve head banging around inside that engine. A sudden stop at TDC will completly destroy that engine. Piston, rod, crank and probably the block and head.

            I've got an old T valve in the shop. I'll cut it open and see how they did them.


            • #7
              If you are thinking about making your own valves, colled roll will work fine for the stems. I have made dozens. Early F-M "z" engines had a center drilled hole at the top center of the valve guide. (horizontal engines)for oil. Yours sounds like a later type zc engine. You might try Ed Deis at hit and miss [email protected] . He has valves ready to go, also try Starbolt.


              • #8
                go here,


                search the archives or ask in a post. also,there are plenty of companies listed that will sell you what you need.


                • #9
                  Here's a photo of how the two-part Model T valves were made. The stem appears to be threaded. I chipped out part of the stem in the right hand half and you can just make out the threads in the head. What doesn't show in the photo is that the top of the stem is flared and extends to the top of the valve head. The second photo shows the top of the valve and the discoloration of the stem area. The top appears to be rough ground (probably by hand) to get the stem flush with the head.

                  It looks to me that the stem was cut with threads and flare then the head was cast in place around the stem. In the first photo, you can see some inclusions in the left-half head under the flare. This fact and the rough underside of the head suggests the valve was cast topside (head) up.


                  • #10
                    Just as an after thought; The stem and head could have been just threaded with part of the stem protuding through the head. A second operation could have been to set the stem like a rivet. This could be done if the head was made with a flare (countersink) on top.

                    After the stem is set, the top could have been ground flush. Doing this way would sure seems like a better way. You would have to make sure the stem was supported on the bottom and sides to keep from bending the stem. (Supported by placing in a hole.)

                    [This message has been edited by CCWKen (edited 05-07-2004).]


                    • #11
                      Great work on the Model T valve disection!
                      I didn't realise they were 2-piece.


                      • #12
                        I'm not too worried about the valve assembly,they could be pressed,threaded and staked or threaded undersized for a jam fit.Intake is a poppet basically,its spring loaded and draws in air on the intake stroke,the exhuast is a push rod,but runs with a light spring and plenty of clearence.Plus its not like is going to be turning at 10,000,heck its rated only for 400 rpm max.

                        I did check the price of the new ones,$26.00 for one $34.00 for the other,so not too bad.
                        I just need one more tool,just one!