Marks Holt 75

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dnalot

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Next I mounted the heads to the rotary table and cut the outer surfaces to size. I then mounted the heads to the cylinders and faced all the heads as a group to insure the manifolds will have a flat surface to mount up to. And then back to the rotary table to cut the details on the top surface.


fin cut.jpg
face cut.jpg
detail cutcut.jpg
 

dnalot

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After shaping the parts I drilled and tapped for the spark plugs and drilled the holes for the valves. And then some sanding and filing to remove any tool marks before sandblasting the parts prior to darkening the cast iron with a gun blue solution.


final cut.jpg
sand blasted.jpg
final look.jpg


I would like to take a moment and thank all that have been following the build. And a special thanks to those that have left a comment.

Mark T
 

gbritnell

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Hi Mark,
Did you have any particular trouble getting the ports to line up with the valve pockets? It's a tight fit between the head bolts. I adjusted the dimensions as much as possible to provide room and not break into the head bolt holes.
gbritnell
 

dnalot

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Hi

No George, I had no problems there but it was a tight squeeze made a bit tighter by me. I drilled the holes slightly larger to make it easier to install the heads over studs. So far your drawings have been spot on, very well done.

Mark T
 

Oldiron

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Did you use a bluing solution on the heads or the same browning solution as on the cylinders? It's hard to tell if there's a contrast in the last picture. Bob
 

dnalot

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Did you use a bluing solution on the heads or the same browning solution as on the cylinders? It's hard to tell if there's a contrast in the last picture
I used a cold bluing solution Bob. It gives steel a blue color but on cast iron it is more black with a tinge of brown. I will be using it on the push-rods when the time comes.

Mark
 

dnalot

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Did you use a bluing solution on the heads or the same browning solution as on the cylinders? It's hard to tell if there's a contrast in the last picture
Here is a photo that shows the contrast a bit better. The parts are rather dusty as machining cast iron is dirty and the dust sticks to everything.

Cylinder and heads.jpg
 

johnmcc69

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I really like that finish, it gives it that old, weathered, patina.

Real nice work all around Mark!

John
 

dnalot

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Time to make some valves. Now there's more than one way to skin a cat, this is how I do it.


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dnalot

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I have made my valves with drill rod stems and stainless heads. The stems are cut to length and one end is tapered to allow the silver solder some room to wick in. The heads are roughed out with the fillet detail cut but not the valve face. And then using a fixture to hold the parts square and aligned to the stem the two parts are silver soldered together and allowed to cool in the fixture. From there they go to the lathe to be faced and to have the valve face cut to 45 degrees. Now the hard part, drilling a .030” hole through the .094” stem for the keeper pin. To make it easy to get the hole perfectly centered I made a simple jig. It was hard drilling and I went through 3 bits drilling through the 8 tool steel stems. 250 RPM worked best.


Valve parts.jpg
Cut Valve Face.jpg
Drill Valve Stim.jpg
Valve parts complete.jpg
 

dnalot

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The valve guides were simple parts turned on the lathe. They were a light press fit but I used a little loctite to ensure there were no leaks.

The seats were cut with a 90 degree end mill. To find the center of the hole I used a precision point and moved the mill's table around until I could see the point was touching the hole on all sides. And then the end mill was used to cut the seat.

I used four grades of lapping compound from 320 grit to 600 grit. And for rotating the valve during the lapping I used a Pin-vice. As a final steep the valves were pressure tested in a fixture.

Valve Seats Cut.jpg
Valve Seat tool.jpg
Valve Test Fixture.jpg
Valves done.jpg
 

dnalot

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Now back to the cat. That's Andy, my feral shop cat after rooting out a Weasel. They are his favorite game because they fight back. Yes he bites and he will kick the **** out of your dog. A total bastard of a cat with catatude. But we are pals and I love him. Nothing wrong with his eye, just catching the light wrong.
 

dnalot

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The Con Rods are made from Bearing Bronze. The first step was facing the ends of the rod and cap before threading for the end cap screws. Once the end cap was screwed in place I cut the stock material down to the proper dimensions. And the the holes were drilled and reamed. Next using a fixture I cut the side profiles. From there I used my turntable to face the rod down to thickness. And then using my fixture again I cut the smaller details. After that a bit of filing and sanding before sandblasting the parts. The rods fit a bit snug on the crankshaft and will require a bit of lapping with a fine compound.


Bronze stock.jpg


Endcaps.jpg


Side Cuts.jpg


Face Cuts.jpg


Small end Cuts.jpg


Detail Cuts.jpg


Ready for Filing.jpg


Conrods done.jpg


So up until now I have been using a .7 to .9 Mbps web connection. Fiber optic cable finally reached my cabin and I now have a 80 Mbps connection. WOW, now I can upload my posts in a single go.

Mark T
 

dnalot

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This post will cover piston rings. My past experience with making rings ended with marginal at best rings. This time I am using the “Trimble Method” and had much better results. I need 12 rings so I made 20 expecting some to be better than others. In the end I had 8 perfect rings and 6 more that required some finessing to make usable. The rest are just (s)crap.

The ring blanks were cut from fine grained cast iron. Once made the rings were honed on both sides to the desired thickness. To snap the opening in the rings I used a sharp chisel mounted in my mills chuck. That worked very well and the breaks were clean and straight.

From there the rings were mounted in the fixture and the face of the rings were covered with several wraps of paper. The fixture was then placed in a crucible with a bit of scrap pipe around it. To help keep air away from the surface of the rings I packed the fixture with a very fine “olivine sand” leaving just the top of the fixture exposed for taking temperature readings while heating in the furnace.

I used my propane foundry furnace to heat the fixture slowly to 1150 degrees and then held that temp for an hour. And then I turned off the furnace, covered the opening in the top with a fire brick and let it sit till it cooled (16 hours)

When I took the fixture out of the sand there was a powdery dust covering the face of the rings (from the paper). That dusted of easily leaving rings with a little soot but no real scale. The rings were stuck together and I needed to use a razor blade to separate them.

After cleaning the soot from the rings I filed the ends to set the gap and then tested each one in a cylinder to see if I could see light between the cylinder wall and the ring. I ended up with two extra rings.

So the next step is to make the pistons and after that I will be assembling everything I have made so far.

Mark T

stock.jpg

parting off.jpg

honing.jpg

snaping ring.jpg

rring fixture.jpg

fixture ready.jpg

fixture in sand.jpg
out of furnace.jpg

fin ring.jpg
 
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