John Smyth 4-1/2 hp Restoration – Part 3 of 5

The cylinder bore on the 1914 John Smyth engine receives a new sleeve.

| June/July 2016

Early examination of the cylinder bore revealed severe rust pitting, and the only way to rectify it was to install a sleeve. It could have been left as was to see if there was any compression, but as the piston required machining of the worn ring grooves it made sense to sort out the bore first, if possible leaving it a few thousandths of an inch undersize so that the rust marks and unevenness of the piston could be removed.

Sleeving the Smyth first involved setting up the engine block for machining, no easy task in view of its shape and size. The old cylinder would need to be bored out, removing enough metal to insert a sleeve and leaving a shoulder at the crankshaft end as a stop for the sleeve. Once the new sleeve had been fitted it would also need boring to size, being supplied undersized. Finally, it would have to be honed ready for the piston.

The first step was to locate a suitable cast iron sleeve, and a search was made on the Internet for a supplier here in the U.K. A sleeve 4.75 inches in diameter with a 4.5-inch bore and 14 inches long would be the ideal fit, leaving 1 inch of the original bore at the crankshaft end.

Nothing approaching this size was found in the online catalogues; however, the nearest being only 10.5 inches long. That length could be used, buying two and cutting one down, but that would leave a “join” that the piston rings would have to cross. Not ideal. Enquiries were made about buying a custom-made sleeve, but the longest that could be made was just 13 inches and the price, with delivery, was quoted at nearly $450.

Enquiries started further afield and revealed a standard Melling sleeve the right outside and inside dimensions, but only 12.25 inches long. However, this was at a far more realistic price, approximately $60. A 12.25-inch long sleeve meant the piston rings could operate within the length of the sleeve. This meant fitting a 1.4-inch collar at the cylinder head end, but it would be beyond top-dead-center and therefore clear of the piston. A sleeve was ordered and shipped to our son in Texas, and with the help of a returning friend the new sleeve found its way to the U.K.

There was no way I thought I could machine an engine of this size with my modest workshop equipment, so the next issue was to find someone who could bore out the block and install the new sleeve. Enquiries revealed a suitable workshop, well recommended and not too far away, so the engine was craned into the back of my SUV and taken there for examination. This shop was quite busy, and the foreman said he could do it in three months — but the ballpark cost was around $650. Another machine shop a friend knew was tried, and while they had the machinery they could only think of problems with the project, so I decided to re-think my options.