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While I'm busy making a crankshaft, I've started thinking of the cylinder liner ID. I'm used to tapered lapped cylinders for two stroke model engines without piston rings. This is the first engine I've dealt with that has piston rings. I don't have any in my collection to measure. Should the...

Well, that dividing head was worth making a plate for. Chucked up a piece of 4140 HTSR on the lathe, turned down the part that will be the hex of the crankshaft, and transferred the chuck to the dividing head. Good fit with the template. I'm happy. It took me all day because I had to true up my...

While fiddling with the female hex template I noticed 3 flats were short. Upon measuring, I confirmed that two opposing sides were 0.005" too close and another 2 were slightly too far apart making the hole slightly egg shaped. I realized it was because the reamed hole I'd put into a hex bar as...

I was looking for a way to hold down my vise since it doesn't have tabs to bolt down with and step blocks are less convenient than I want when I'm moving the vise around alot. I think a low profile version of this is the way I'm going to go! Many thanks for posting this.

I forgot an important part of making this tool. Rather than bringing the dish on the end right out to the tips, it should be brought to the flats instead, and then using a dremel or a file, file the end relief out to the tips and the flats. It shouldn't have a scalloped edge like the above photo...

Woo a workable conrod! I had to make 3 of them for the junk bin before I got one that I didn't mill too far into the bearing end. It's nowhere near pretty. It's too difficult to do a rotary table style end with my slow maximum rpms on this mill. Breaking 1/8" endmills all week. if this thing...

I agree. I come up with my best ideas just as I'm falling asleep 3 days after I first start thinking about something.

I suppose if you keep that cut shallow enough you avoid making too wide of a seat. Thanks! I'll give that a shot.

another thanks! I was going to cut the seats with the valve guides on the lathe and then press them in but I guess I'll change my tactic and plan on making a seat cutter. Would it be safe to thin the seat on the lathe (cut the angle on the face, and angle in the throat, of a 3 angle seat), but...

yes! a friend had enough 7075-T7 (Nice and hard.) to make a pile of connecting rods. With the reamer cut short it runs true. I'll stick it in a collet and keep going.

And valve overlap and flow probably has something to do with true compression too, right?

Heh yeah that's exactly what I did. Subtracted the assembly from a slug at tdc and bdc. Worked well, but the results pegged my BS meter. Guess its accurate.

In those case I worked hard on making a domed piston and cutouts for the valves. If I go with a flat top I think it solves the problem and avoids 4 more setups and operations.

Thanks everyone, back to the drawing board!

3d CAD is amazing sometimes, but sometimes it makes me start from unreasonable assumptions which then makes me question my math. Right now, it's throwing off my estimation skills by being so far out of the ballpark I must have messed up with my calculator. I can easily determine the...

first major errors today! I quite accurately hit the dimension I held in my head, but unfortunately the dimension was for a different part of the connecting rod, so I cut a flat too far. It had dug into the bearing surface too far to be salvageable, so I decided to start over. I didn't have any...

Tough to beat cast iron and steel combinations for wear and longevity. Steel liner and a cast piston is a really good bearing surface. That said, most commercial model IC engines use a brass liner that's been hard chrome or nickel plated. The smaller ones use an aluminum piston, and lap a...

Looks super good gus! I love it when they start taking shape!

Very cool. Signing on to watch!

Yeah I went back and added smaller sizes to them all, hope it helps