So, this post is going to start a rather long series regarding valve guides/seats and valves. Currently there's a sad ending but hopefully I'll get to a happy ending sooner or later.
Since this is all a bit of a learning experience for me, I decided to make the valves by 2 methods, just to see which one worked best for me. So to start, I decided to try the 'silver braze the valve head to stem' method. So I cut 2 pieces of 3/32" drill rod to 1.00" length and drilled the retainer hole in the end using a collet block in the mill vise. The hole was only .040" (#60 drill) so I put a penny coin next to is just so the hole was visible.
Both completed 3/32" valve stems laid on the print.
For the one piece valves, since I'll be turning down the stem, I made a gage out of brass. I just drilled and then reamed a 3/32" hole thru a 3/8" x 3/8" long bit of brass stock.
Next on to the valve guides/seats. This is just a view of turning the taper on the end of the valve guide using the compound. Nothing terribly exciting here. I made these out of ordinary 360 brass based on the advise from Brian Rupnow and others. This seemed completely sensible to me.
Here's one partially finished. The OD is completed, but the ID has to be completed.
Starting on the ID features. First, I drilled thru and then reamed with a 3/32" reamer.
Then drilling the larger ID to the called-out depth on the print.
I didn't take a pix of critical operation which may turn out to be good or bad. But at this point, without removing the guide from the collet, I took a 90 degree countersink and lightly touched the lip of the guide to form the valve seat. It certainly didn't chatter and it LOOKED good upon casual inspection.
The top view of the finished valve guides.
The bottom view of the finished valve guides. If you look carefully, you can see the very narrow 45 degree seat formed by the countersink tool. Comments if this approach is good or bad are welcome!
The valve guides/seats assembled into the valve blocks. They were a very easy press fit and I applied Loctite 603 when assembly.
The back to the mill. After carefully locating both holes, I drill thru the brass valve guides/seats with the called out drill. The operation went perfectly fine.
The completed valve blocks after the guides were Loctited in place and drilled thru.
I, non-so-cleverly, managed not to take any pix of making the valve heads for the 2 piece valves, but here's a pix of the 2 valve bits assembled, but not yet brazed together. This was pretty straightforward as I turned the tapers after setting over the compound at 45 degrees using an angle block to assure some sort of precision. The hole thru the center of the valve heads was reamed to 3/32"
![](https://lh3.googleusercontent.com/pw/ACtC-3du9Dzdu5aUIQgX3h5gwcqWwJzYZeyBSOZXVaArv2MdJsR72N7uXKhcOnzcERSFF5N3SVol2fbmD7QhkGhKa34g3YvihLjw_aMfFXHXgxCYL6SRQx7pYnpooI3TInzHqHFiWW4nWk_Xo8aD0tmBJwmi=w711-h947-no?authuser=0[img]<br /><br />Then after several failures I managed to turn the valve stem diameter down using Brian Rupnow's method of turning down only about .30" of the stem at one time and then progressing the cutting until the full length required is achieved. I learned that you need to be very careful and very deliberate as it's all too easy to bend the thin stem material or cut a taper on it. But after a few attempts, I was successful.<br /><br />[img]https://lh3.googleusercontent.com/pw/ACtC-3dhdpgC56H_4mITyojXnx-YEA6w9lJAUIt1rI27JsiziQgMt16nnwfEvnFYbQyLbb0buSgODfAfNd-BBswVt0aeZdpOBv-JBQtzwA9gKNThN6hfgLYXyIgQlFKY7jtWtITgIMNue_SRRXsSCFKL3z2v=w711-h947-no?authuser=0)
Using the gage to make sure the valve stem is uniform along its length. I used some fine emery cloth to work the stem at any tight places until the gage slide smoothly along the length. I think that this worked pretty well as the fit is very close but the gage still moved freely.
Here's the lathe setup for turning the valve faces at 45 degrees. I had some difficulty understanding how I'd set this up, but after a bit of thinking and playing, it became clear. One thing I learned is that if you leave the tool holder set in the normal position, that is perpendicular to the lathe axis, you can cut the stem to diameter using the carriage and then cut the valve face by using the compound without screwing around resetting the tool. The compound advanced the tool from the stem diameter to the outer face diameter using this setup. This certainly saves some time and aggravation and I think make the end result a bit better.
Closeup of the valve face being cut.
Moving back to the 2 piece valves. I cleaned the valve stem and head with acetone and then applied flux to both pieces. I cut a small piece of silver braze material and laid it on the top of the valve head. I applied heat with my Victor torch using a 000 tip. The brazing goes fast with this setup but worked fine.
Both 2 piece valves after brazing.
And after cleanup in the lathe. You can see the uniform silver braze material at the interface between the valve head and the stem.
So, it looks promising, right??? We'll I decided to do at least a basic check to see how true the valve seats were with the stem. So I chucked up the valves, both the 2 piece and 1 piece valves and put a DTI on the valve face as shown in the pix.
In the end, there was great sadness over the 2 piece valves. One of them ran out about .0025 and the other one about .0055. I ended up making 3 one piece valves and on the 2 best ones, one of them had imperceptible runout and the other one had just a few tenths runout. So I decided to use the one piece valves going forward for this engine.
In retrospect, I realized that I made a fundamental error when making the 2 piece valves. I should have just cut a disk of .250" material and drilled and reamed a hole thru it and then silver brazed that to the stem. Then after the brazing operation, I should have then cleaned up the top of the valve, AND I should have cut the valve seat at 45 degrees at that time. Apparently, even though I had drill rod and a reamed hole, there's enough clearance between the 2 pieces so almost guaranteed that they'll be crooked. And of course by turning the seat area prior to the brazing operation, I didn't have enough material left to true it up. So those 2 piece valves went in the trash.
Here are the best 2 one piece valves that I ended up with out of the 3 I made.
So with all the tales of valves not sealing, I decided it would be prudent to make a test rig for the valve block assembly. I just milled and drilled a piece of .25" AL and installed a press-lock tubing fitting that had a 10-32 thread with an o-ring seal on it. Shown is the test fixture assembled onto the valve block.
And the regulator assembly I made. I purchased a cheap regulator from Harbor Freight and installed an air coupler to get to my shop air supply. Then there's a 1/8" barb fitting going to the test adapter for the valve block. Pretty simple, but I wanted something like this for a long time as it makes applying air for test or running steam engines very easy.
I'll add just a few more pix to round out this part of the story prior to getting to the actual testing. I made some the valve retainers, modified from the Webster plans as the original design didn't seem capable of retaining the pins. Due to a series of stupid mistakes, I ended up making 3 different sets before I finally got to these.
The retaining pins. I cut these from a safety pin since I found one with a wire diameter of .039 which perfectly fit thru the valve stem hole. Simple but aggravating as they're small!! I put them on the adhesive side of some masking tape to prevent them from escaping as I'd never find them again!
Showing a valve, a valve retainer, and pin all assembled.
I also needed to make springs, so based on a spring winding guide that I saw on a YouTube video, I made one as shown. The idea being that wire up to the hole diameter can be wound and the V at the end will force the wire over regardless of size, up to the limit of the hole size. Material was a piece of random 1/2" steel rod that I had laying around.
Shown is the actual making of a spring on the lathe. The tool and method worked out well. That a 1/8" mandrel that I used for the intake spring. Wire was .012 guitar string from a local music store. They refer to it as '12 gauge' string. To start the spring, I drilled a .040" cross hole near the end of the mandrel and then advanced the spring winding with the lathe setup for threading. I did practice a bit and found that I could wind starting and ending coils by simply disengaging the feed, and the body of the spring was done with the lead screw engaged and the lathe running at the slowest speed possible.
The finished inlet spring made from .012 wire.
The intake and outlet valve blocks fully assembled, prior to lapping and prior to cutting the valves to length. The larger exhaust spring was from .022 guitar string and I ended up having to make a mandrel out of 3/16 drill rod turned down to .145". I used the Machinery Handbook music wire spring winding table and found it to be very close. I did try the 1/8" mandrel and a 3/16" mandrel and both sizes were wrong, but the .145" mandrel was just right!
Commencing lapping. I applied a bit of TimeSavers extra fine grit mixed with a bit of oil. I was conservative with the oil so the lapping paste was something like thin grease. I didn't want it running everywhere so I mixed it on the thick side. It's hard to see but it's the dark green substance on the valve face.
Both valves after lapping. You can see the burnished area on each valve. That burnished area is continuous so at this point, I thought i was successful. When lapping I rotated the valve with my fingers with only light pressure, about 90 degrees for about 20 repetitions. Then I picked up the valve and rotated it 90 degrees and repeated the lapping motion. I did this until I went 360 degrees, then applied a bit more lapping paste and repeated the lapping cycle.
Then I cut off the excessive length, the handle if you will, from each valve and cleaned up the tops. I was also careful to make sure each valve went back into the same seat it was lapped to. I scribed an 'I" and an "E" on the valves so I could keep track of them.
The valve block fully assembled with gaskets! I had high hopes of success at this point.
All rigged up and ready to test. I immersed the assembly in a plastic container of water and got ready to apply the air. Still full of hope at this point!
I know its hard to see in the pix, but I did carefully examine the block assembly during the testing and I can assure you that both valve were leaking at very low pressure. I tried several things, putting a bit of oil into the air inlet port, pulling on the valves by hand, rotating the valves a bit by hand while applying air and absolutely nothing made any difference.
At this point I've disassembled the valve block assembly and started thinking about the problem. By eye, everything looks ok, but I need to find some sort of magnifier to look at the valve face and seat more carefully. My current theory is that the lapping process wasn't adequate. I'm questioning the use of TimeSaver's grit in this application. I've ordered a small can of 600 grit Clover carborundum paste, mostly based on what Brian Rupnow recommends. My theory is that perhaps the sealing surfaces are not finely lapped, at least not enough to seal low pressure air. I'm waiting on the shipment of it to arrive.
Also I've carefully read what many people do and I've started questioning my use of a 90 degree countersink to cut the valve seat on the lathe when I made the valve guides. There are lots of references to using a piloted valve seat cutter. So if further lapping doesn't work, I made try one of those. Comments on this point??
Also can anyone comment on my testing method? It seems entirely reasonable to pressure test with air as shown. But there are a number of people that seem to test with vacuum, and I'm not exactly sure as to why?? The pressure or vacuum methods would seem equivalent, and I actually think that pressure being applied would more accurately represent the actual running condition of the engine.
So, I'm open to any and all suggestions! I was a hopeless optimist and I've fully fallen into the valves not sealing trap.
Please let me know when you think!
Mike
