When I get the GMS engine from wjames, and I make a diesel head for it, if anyone is interested I will take photos of each step as I go through the process and post here in a thread, along with a description.

That way, if there are some of you fellows with access to a lathe, perhaps you will want to try one for yourself?

Let me know if at least a couple of guys want to see it I will bother to take some pics, if not, thats OK too...

Andrew

Hey Andrew, I'd like to follow you through your project. Dave

I would definitely be interested in the project.

Ok then...

Andrew,

In my dreams I will have a metal shop with my hobby room and make my own diesel conversion heads and steam engines. Yes keep us posted.


Oily in Germantown
Francis

Sure, keep us posted. You may make them differently from the way I do it. How do you fit the contrapiston? With an O ring or the old fashioned way? I have had success with using a brass contrapiston as well as aluminum and steel. What is your experience/preference? Just curious.

Max

I have mostly made lapped cast iron or steel contra's in a steel sleeve. I have had some good success over the years also with Viton O rings, usually I fit two. I have not tried aluminum or brass.

For this engine conversion, I am going to machine the head from 6061-T6 aluminum and make the contra from aluminum also. I will use the twin O ring method to simplify things. If fit with close tolerances, the O rings last a long time, but if your contra is fit loose they burn up fast.

I didnt get the engine today in the mail so it isnt going to happen this weekend. Maybe next!

AJC

What rotten mail service just kidding .
Should be there soon.
have a great day everyone.
Wade James

Got the engine today Wayne. I will start soon. I picked up the Viton O rings during my lunch hour today and got a few spares for you.

Hopefully start machining soon...

Andrew

OK guys here is a picture lesson on how to make one diesel conversion head.

Step # 1, size the aluminum bar to the head outside diam...

Step #2, bore out the interior of the head to the same ID of the cylinder, and step the bottom to fit over the cylinder top..

Step #3, part off the head blank, turn around in the chuck and face the top, round the outside edge, and drill/tap the head for the 10-32 adjustment screw...

step #4,

DRill the holes for the head bolts - I use a small rotary table for accuracy.

step #5, counter bore the head for the correct depth for the screws...

step #6,

on the mill, cutting the head fins with a slitting saw

Step #7 - rough the contra piston blank to 1.5 to 2 thousandths under the cylinder bore

step #8,

Using a round end toolbit, cut the grooves for the O rings...

Step #9,

After finishing the O ring grooves, turn the combustion chamber side, then part off the contra piston, turn it around and face the top and use a ball end mill to make a dimple that the adjustment screw will sit in.

Step #10, install the O rings and check the fit of the contra into the head. Use grease to let it go into the head without damaging the rings

finished results!

The engine with newly made head, mounted and looking sharp

Final step, put it onto the test stand, fill the tank with some Davis Diesel mix and prime. If you are lucky - and I was... - it should fire and stay running after a few flips!!

The GMS was very easy to adjust. I had to close the Low speed needle 1/4 turn, and close the high speed about 3/4 turn. The contra was adjusted, and hot restarts were easy. Compression is tight and snappy, makes starting easy. The throttle response was way better than any of my 4 Irvine 40 diesels I had.

Only time will tell how this engine holds up and runs as a diesel, but as you can see the head was no biggie to make. Total time was about 3 hours of liesurely machine work.

I was runnign an APC 12-7 prop, but due to it being dark, I couldnt tach it. Sounded lovely though!!

Andrew J. Coholic
ajcoholic

Andrew
It looks great ,glad to here you think it runs and sounds good.
Now to start mixing diesel.
Thanks again Andrew.
Wade James

Andrew,

Would you give the approximate depth you bored out the head for the contra piston?

Thanks,

Will Varnado

Sure I will.

I made the contra piston 3/8 thick. The head itself is 7/8" thick. The bore for the contra piston is 1/2" deep and the step that sits on the top of the cylinder is 1/16" deep, so measured from the lower lip the bpre for the contra is really 9/16". Follow me? That leaves 5/16 on the top of the cylinder and I cut the fins about 3/16" deep (leaving 1/8" solid material)

I used a 10-32 machine screw for the adjustment.

One thing, you may notice differently that I do, is "key" the head using the outer diameter of the cylinder sleeve, and make the bore of the head the same as the sleeve. The contra can then move up/down in the head and sleeve - the head effectively lengthens the height of the sleeve.

Unlike other conversions (DDD for instance - if I make out the pics correctly) that use a smaller diameter contra than the cylinder bore, and the head fits into the cylinder sleeve like a normal glow head.

AJC

Appreciate your comparison with the commercial heads, as I (being highly hypothetical here) would have done it like the commercial heads, and didn't exactly understand what you were doing. Now I understand why you are using two 0-rings.

Good Show!
Jim