Peter Rooke tackles a tough IHC restoration project – Part 1


Peter Rooke’s latest project, a 3 HP IHC Model M.

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I had mentioned to an engine friend that I had considered purchasing an IHC M for restoration, but thought the price was too high, so I left it. A week later he telephoned to say he knew of another 3 HP engine, but that it was very rusty and if I was interested he would send me some photos. He was not joking.

When I saw the photos it was in appalling condition, just as I like them, and better, the price was reasonable. Even more good news, he had to travel to Dorset, a 400-mile round trip, to collect another engine, so he could pick mine up for me. Two weeks later, I travelled a short distance to his engine store to collect my engine, which we man-handled onto my trailer for the journey home.

Once home I used a chain hoist to lift the IHC off the trailer and onto rollers, so I could move it around the workshop. For the first time, I was able to examine the engine carefully. Everything was there including the crank greaser, but the oiler was long gone. I later found the broken lower section in dirt at the bottom of the water hopper. From the serial number it was possible to date the engine from 1920, fitted with the more common overstrike igniter. It soon became apparent that while a lot of work would be involved, the restoration should be fairly straight forward. There are lots of parts and information available for this engine, although they are not too common here in the United Kingdom.

Before stripping the engine, it needed some cleaning, so I rubbed it with a wire brush then moved it onto a plastic sheet and liberally coated it with oil. I left the engine for a couple of weeks and in that time coated it once or twice a day with oil. Given the condition of the engine, I guessed it had been stored alongside fertilizer sacks, and the dust from those had covered the engine and advanced the rusting process.


To start the stripping process, I removed the brass pipes and their fittings, as they are difficult to replace. Being brass, they had not rusted in position.

The flywheels and pulley were going to be a problem in view of the amount of rust, so they were liberally coated with penetrant. The cover for the gib key and the crank grease cup were removed, the former by drilling out the screw. The remains of the three other grease cups were removed - they all needed replacing.

To prevent any damage to the governor, the ring was unbolted from the flywheel. Fortunately, it had been covered in grease and the securing bolts had not rusted and were loosened with a wrench. The weights were immovable; the springs had long since rusted away so the pivot pins for the weights were cut through with a hacksaw and a miniature cutting wheel.

The governor fork was rusted firmly in place and the rod to the mixer butterfly could not be moved. It was cut off either side of the fork, the remainder being drilled out of both the fork and supports on the lower bearing casing when the engine was stripped.

Removing the pulley and flywheels

Removal of the gib key locking the pulley was complicated as the pulley rim extended over the end of the crankshaft, which made it impossible to remove the key with a wedge and hammer. Rather than weld a rod to the end of the key and use a slide puller to pull it out, I decided to drill the key as everything was badly corroded. It was also necessary to drill the locking screw, which was stuck fast and didn't budge even using an impact driver. The exposed areas of the crankshaft, including the keyway, were cleaned with a file and emery cloth to remove all ridges, nicks and rust. The crankshaft was covered with a liberal coat of penetrant. Once the key had been drilled, the pulley was twisted off and the remains of the key removed.

The keys, flywheel hubs and crankshaft had been soaked in penetrant for a few days after first shocking the keys with a hammer and brass drift. The key heads were squared with a file and a homemade key drift clamped to the crankshaft to remove the key. As expected, the heads sheared off and, again, I had to be patient and drill out the keys.

To drill the key, a 5/16-inch hole was drilled in a piece of 7/16-inch diameter rod, the width of the key. I chose this size of drill because I had a newer long shank drill, which was accurate to start a pilot hole. I prefer to start small in case I hit a problem and need to straighten the hole. If necessary you can soft solder an ordinary length drill to an extension piece to get the required length.

The drill guide was clamped to the crankshaft, tight against the broken key. The secret of deep-hole drilling is to keep the drill bit well lubricated and to keep clearing the swarf, by frequently withdrawing the drill. Firm, even pressure was applied to the drill and plenty of patience was needed to allow the drill to do its work without forcing it. Once the pilot hole had been drilled, it was opened using progressively larger drill bits to a fraction under 7/16-inch.

Efforts to twist the flywheel and break the remains of the key failed, so the hydraulic puller was used. Even this was a struggle, so I had to hit the hub of the flywheel with a hammer and drift while it was under tension from the puller. There was a resounding crack and the flywheel started to move. Care was taken throughout to ensure any pressure or force was only applied to the flywheel hubs to prevent any possibility of breaking the flywheel spokes.

Removing nuts and bolts

The key to removing rusty nuts is to have a wrench the correct size for a tight fit. Unfortunately, the hexagon sides to the nuts were, without exception, badly corroded. The object in these cases is to prevent damage to the studs, thereby complicating the restoration by having to replace them. Where there was room, the sides of a nut were cut with a hacksaw or removed with a small hand grinder. For the more difficult positions, the nuts were split with a cold chisel and lump hammer. This, of course, meant that a large number of nuts and some bolts had to be replaced, meaning that several days were spent making replacements.

As mentioned already, the governor rod was rusted solid in the fork holder and the cylinder head. Similarly, the exhaust pushrod was immovable. The rods were all sawn through so the cylinder head could be removed. At this stage, I noticed the exhaust rod support was broken and would have to be repaired. The remains of the rods refused to move easily despite soaking in penetrant, so they were drilled.

Once the mixer and cylinder were removed, the bolts securing the bearing caps were unscrewed and the caps were taken off. Care was taken so that the bearings were not damaged and the shims were stored safely until needed. The crankshaft, gears, connecting rod and piston were removed. Externally, the engine was in a bad state, but internally, there were no problems; the bore, piston rings and bearings were all perfectly serviceable.

Finally, the fuel pump eccentric and follower were removed and the engine turned over to get at the fuel tank, which was just a rusty shell.

The IHC casting was cleaned using a wire brush and scraper, and the threads on all studs were cleaned using the correct sized die. Internally, all parts were washed with kerosene to remove years of grease and grime. As the inside of the engine was in good condition, the cylinder sleeve seal was not changed. This later proved to be the correct decision as there were no leaks when the hopper was eventually filled with water and the engine run. Earlier, the engine block had been taken outside and pressure washed to remove all mud from inside the water hopper. At this stage, the remains of the oiler and feed tube were found wedged down the side of the cylinder.

Once the engine was in pieces all parts could be examined and decisions made on what to make and what to buy. While just about everything needed could be purchased, numerous items could be made, which is part of the challenge when restoring an engine. I decided that I would purchase a new fuel tank, grease cups, some pipe fittings and springs from Hit & Miss Enterprises, but would make nearly everything else. A replacement magneto would also be needed as the original was beyond repair.

Cylinder head

The engine cylinder head would require extensive restoration with the majority of parts requiring replacement. The connection pipe to the muffler had rusted so badly that it would have to be replaced, but the elbow, while badly corroded, was passable. To re-duce any risk of damaging the cylinder head, no attempt was made to move the elbow. But in order to replace the pipe, it was necessary to cut the muffler with a hacksaw, then remove the remains of the pipe by sawing it lengthways before splitting.

The operating camshaft for the broken butterfly was removed by cutting the brass pivot pin. The spring had long since disappeared and when trying to remove the activation rod, part of the camshaft disintegrated. After cleaning the body of the camshaft a new plate was fashioned and brazed into place with a new pivot pin for the link to the governor. A piece of 5/16-inch brass rod was slit and screw holes tapped for a new butterfly, which was made out of 1/16-inch sheet. The size was marked with a compass before carefully filing it to fit, taking care to get it exact. The holes for the mounting screws were drilled, then opposite top and bottom edges of the butterfly were tapered for clearance to allow it to close fully.

The original adjustable link to the governor rocker shaft had virtually rusted away so a replacement was fabricated from pieces of steel to match the estimated dimensions of the original. A return spring was made to complete this part of the restoration.

While the nut holding the rocker arm pivot eventually came off, the pin didn't move, so the head of the bolt was cut off and a press was used to push the remains from the top.

The governor rod and exhaust pushrod were drilled and finally the valve stems were sawn off close to the top of the guides. Again, they were seized solid and it was necessary to set up the cylinder head on the drill table and drill through the stems. A file was used to clean the remains of the valve stems, cutting slightly into the top of the valve guides so the full diameter of the rusted stems was visible. This enabled accurate use of a center punch to mark the center before drilling a pilot hole through the stem. Drill sizes were gradually increased until the hole was close to cutting into the wall of the valve guide when the remains of the stem were pressed out. The holes in the valve guides were tidied using a 3/8-inch hand reamer. The exhaust valve head was salvageable, but the inlet was so badly corroded the whole valve was scrapped.

New valve stems were made from some 3/8-inch drill rod. For the exhaust valve, the remains of the old stem were drilled out of the head, which was brazed to a new stem. A completely new inlet valve was made using a disc of steel for the head and drill rod for the stem. They were brazed together and the lathe was used to profile the head to match the original, although it was made a fraction wider. The inlet and exhaust valve seats were corroded and as the damage was extensive, the seats were first cleaned with a file and the heads ground using valve grinding compound.

The repair to the rocker arm pivot was not quite straight forward. The original appeared to have a floating sleeve between the threads and the head of the bolt, so the only way to duplicate it was to fabricate a replacement. Taking dimensions from the original, the various components were machined and the sleeve and stem were given a thin coat of oil before being assembled and the bolt head brazed on.

The final problem with the cylinder head was the guide for the exhaust pushrod, which had broken. To start the repair, the guide was Super Glued back on to the casting in its correct position. Two 1/8-inch holes were drilled lengthways through the broken piece into the main casting and small escape holes were drilled in the main body to allow any air trapped to escape when brazing. Once the holes were drilled, the piece was broken off by exerting lateral pressure and all vestiges of the Super Glue removed by cleaning both sides of the joint with a small grinding point.

As the cast iron was badly oiled some flux was applied and the area was gradually heated, bringing it to brazing temperature for the flux to draw out any oil and impurities. It was necessary to repeat this stage three more times.

When satisfied that the metal was clean, the tie-rods were fluxed and inserted, the faces fluxed and it was all held together with a small clamp, ready to braze. As normal with cast iron repairs, it was heated slowly and the heat maintained when finished, to allow the temperature to fall gradually for slow cooling. The flux allowed the braze to flow around the tie-rods, locking them in position and strengthening the joint.

To repair a crack in the head of the guide, the pushrod hole was enlarged by drilling it 1/8-inch oversize and a sleeve turned to fit inside making it slightly longer than required. It was drilled to the diameter of the pushrod. The crack was cleaned with a file and impurities removed using the heat and flux method. After cleaning everything again with emery cloth, more flux was applied and the sleeve brazed into the head and finished by drilling a new lubrication hole and filing the ends flush.

Read part two in the next issue, restoring the fuel pump and igniter.

Contact Peter Rooke at: Hardigate House, Hardigate Road, Cropwell Butler, Notts, England, NG12 3AH; peter@engineerpeter.co.uk • www.enginepeter.co.uk