Water Pup

A 4 cylinder water cooled gas engine

Several years ago in HOME SHOP MACHINIST, a series of artiles was printed detailing a 4 cylinder gas engine. I was interested in building a 4 cylinder, engine, and had been for years.

When I was in Jr. High School, about 1957, I had a couple of drafting courses. I really got into it, and for an extra project I decided to draw all the parts of a 4 cylinder enginge from a magazine I had. I think it was a Popular Science or Popular Mechanics. I drew the entire engine, and in the process learned a great deal about engines.

If anyone knows what magazine ran a 4 cylinder engine about 1956 or 7 I would really like a copy. Ive long since lost all those drawings,and now would really like to build that engine

After the entire series was printed, I read it over a few times and decided to build it, but with a couple modifications.

Panther Pup is air cooled, and the article noted the cooling was very poor, resulting in the engine only running for short periods. The engine I rememberd was water cooled.
The valve rocker shape is bad. Its a T shape, with the pivot at the base, causing a large side force on each valve, not just a push.

I made my own patterns and had them cast in aluminum by a friend. The crancase halves and gear cover were exactly like the article. For the cylinder block I made a shape like marine engines of about mid-1920's. I made a core box to make the block hollow for water passage, and pressed in cast iron sleves for cylinders.

Here is a photo of the patterns and core box. Note the block is just a simple rectangle. I later made a new block, with a better shape, but never took a photo of the pattern.

Heres a photo of the crankcase and block assembled. Note the new block shape.

Crankcase

For the crankcase and all its parts I basically followed the PUP plans. If I were doing this again, Id make a few changes. I'd add oil seals to the crankshaft bearings. My engine throws oil badly. I'd also look at adding some drilled oil passages to the crank, and an oil pump dirven off the cam. Look at the MASTIF plans for some good ideas on this.

Camshaft

I made my camshaft in one piece, not with added on lobes. I turned the shaft from a single rod, with round sections at each lobe turned to the major diameter of the cam. I then setup a jig to hold this cam under my surface grinder, with some springs to push it against the wheel. I made a master cam, in the dividing head on the mill, using the BASIC program from SIC for angles and offsets.

I made my first attempt from drill rod, and tried to harden it. It warped badly, and a slight attempt to straighten it broke like glass. I then got a rod of 4140 steel and turned it from that. Should be hard enough for reasonable use.

Cylinders

The cylinder block has pressed in liners. The liners were turned from continious cast iron (Durabar). This is beautiful stuff to work with, it turns well, and leaves a nice finish. I honed the liners after pressing them into the block, with a simple split aluminum lap.

I made the pistons, rods, etc according to the article. I made the rings following the process described in SIC Starting in Vol 2 No 7. The photo shows the heat treating jig, the cleaver jig and some finished rings.

Head

I wanted the head to have water passages. This got to be real tricky. There are MANY holes in the head, with valve guides, passages, hold down bolts, rocker supports, manifold attachments, etc, etc. I made the head in two pieces, the lower part a slab of aluminum 1/2" thick, the upper a cover of 1/8" aluminum. These were bolted together for the drilling of all the holes.

When all the holes were drilled, I removed the upper cover plate, and put the lower part on the mill. With a ball end mill I went all around the head, removing all the material I could between the major features. This left water passages above each combustion chamber and between all the valves. I drilled a series of holes between cylinders to allow water to flow thru to the block.

The photos shows the head iwth the cover plate removed. also in this photo are the pistons, rods, and rings.

Details

As with a lot of projects, this took MUCH longer to build than I thought. I have finally been able to get it to run, but it blows head gaskets after only a few minutes. I've been making paper head gaskets, and obviously that wont work.

This final photo shows the almost assembled engine.