This story started in 1995 when a gentleman from the Dalton, Minn., threshing show had some engines for sale.
Among these engines was a 1919 9 HP Type E Economy. The engine was mostly complete, but was missing the ingiter and magneto, and the igniter port was open. It was also stuck, with the piston all the way back. Had the mice and moisture had their way with the cylinder bore? I had no idea.
Taking a chance
I wanted the engine but did not buy it. I looked at it again a year later but still, no deal. In mid-winter 1997, I finally purchased the engine on a handshake as the owner wanted no money until I picked it up in the spring. Several weeks later, the owner’s obituary was in the local newspaper. I thought for sure the Economy deal was broken, but I contacted the family at a later time and they assured me they knew about the agreement and that the engine was still available. More good engine people.
Worst fears realized
When the weather allowed, I picked up the engine and started the restoration. It took a week to get the head off, and my fears were correct – there was a huge mouse nest and lots of nasty pits in the bottom of the cylinder bore. I cleaned and polished the bore and filled the bits with a two-part epoxy (LPS Tough Titanium), honed the cylinder, re-grooved the piston ring grooves, installed a set of Joe Sikes custom rings, as well as new valves, gaskets, igniter and magneto. It ran, but it also splattered a lot of black oil all over the back of the engine. I ran it that way for several days but it lost compression and eventually wouldn’t start.
I had to fix the bore, but with limited funds for the project, I had to look at lots of options. I have a machinist’s background and for years worked in the heavy equipment maintenance field. A common job back then was to repair worn bores on heavy road and mining equipment with portable line boring equipment. We would bore the worn area and press a sleeve in, or weld the bore and machine it back to size. I decided to use this method to oversize the bore and then make an oversize piston. This engine has a 6-1/2-inch bore and a cylinder almost 2 feet long, and most engine rebuilding shops could not machine a bore that long.
DIY engine rebore
I had to fabricate most of the tooling to machine the bore. The tooling included two self-aligning 1-15/16-inch ball bearings; a boring bar of 1-15/16-inch cold-roll steel shaft; two universal joints; a length of 1-1/18-inch hex shafting and a 1-1/18-inch sprocket hub for the hex shaft to slide through; another self-aligning bearing on the end of the hex shaft; a machined boring tool holder; a 1/2-inch brazed carbide boring tool; two centering rings; miscellaneous steel; and spacers, adapter plate, nuts, bolts, etc.
The centering rings were made of 1/4-inch plate and were used to align the boring bar in the center of the cylinder bore, then removed. The outside diameter was 6.500 inches (cylinder bore size) and the inside diameter was a slip fit on the 1-15/16-inch boring bar. The head end was bolted to an adapter plate which fit loosely over the cylinder head studs. A set of pipe spacers held the bearing far enough away to allow removing the centering ring and give the boring tool clearance. Nuts and washers clamped it all together. The rear bearing was bolted to a fabricated bracket which was bolted to the main bearing cap bolts and the cylinder mounting bolts. This bearing was shimmed to get the correct alignment.
The centering rings were then installed in the cylinder, one on each end. The boring bar was slipped into the rings and the bearings slipped on the boring bar. The front bearing assembly, spacers, nuts and washers were assembled and tightened evenly. Some light tapping was required to adjust the alignment for the bar to turn freely, and the rear bearing was shimmed to allow the bar to turn freely. The bar was then removed, then the centering rings, and the bar with the tool holder on it was reinstalled.
The engine was parked about 10 feet from and directly to the left of the headstock of my 1942 16-inch-by-102-inch Monarch lathe. The drive shaft was connected to the boring bar with a universal joint, which was connected to another universal joint and then to a 1-1/18-inch hex shaft. The hex shaft went through the spindle and through a 1-1/18-inch hex sprocket hub that was clamped in the chuck. A bushing was installed in the left side of the spindle bore to keep the hex shaft in line. This provided the rotary motion to power the boring. To feed the operation, the end of the hex shaft was turned to fit into a ball bearing, which was then fitted with a self-aligning collar that was bolted to a bar clamped to the cross slide tool holder. The feeds and speeds were controlled with the lathe controls as in a normal boring or turning operation. As the universal joints were not in line, we had to start the boring operation on the back side of the engine and pull (or feed) it toward the front.
The cutting tool was then installed and adjusted for depth of cut, the tool holder clamped, bearings and shaft oiled, feed and speed set, and the lathe started. It worked like a charm and the heavy bar did not chatter. It took one rough cut then a light finish cut, for a total cut of 0.100 inch to clean up the pits and get a good finish. In all, it took several days to set up and about 1 hour to machine it. The end result was a bore straight and round within 0.001 inch the total length of the bore. A Sunnen hone was then used to remove tool marks and get a good finish.
Regarding the piston: On other engines with worn bores, I’ve honed them with a Sunnen hone until they were straight and true, and then built up the piston with a Eutectic metal sprayer and had custom oversize rings made. Usually, these were only 0.015- to 0.030-inch oversize and they worked out well. But this bore was 0.100-inch oversize and metal spray does not usually work well in such a heavy build up. So, I chose to make a new piston out of steel.
I started with a piece of heavy wall tubing, which I machined to the inside diameter dimensions of the old piston, and then I drilled a cross hole for the piston pin bosses. The bosses were made of steel tubing and were beveled on one end to insure a complete weld. They were held in line and positioned with an alignment pin, then welded on the inside from both ends of the piston. The outsides were then welded. These welds were cleaned up, and the head of the piston was welded in place. The piston was then normalized and cooled. It was then turned to fit the bore, and the ring grooves were cut. The last operation was to machine the piston pin bore, and drill and tap set screw holes to clamp the wrist pin. A set of Niagara custom +0.100 oversize rings completed the job.
Well worth the effort
The engine runs well now and has been used to buzz firewood for my fireplace. I did install a Wisconsin air-cooled engine with a gear reduction as a starting engine. It is mounted on a slide, and uses a pneumatic tire as the friction drive against a flywheel. It sure beats trying to turn the engine by hand!
Contact Howard Kittleson at 13540 Cty. Hwy. 30, Pelican Rapids, MN 56572 • firstname.lastname@example.org