Having recently had two major failures in my type 7 (20hp.) Stanley engine, I think it advisable to describe them as a warning to those who drive their cars a great deal.

Last year, a crank failed at the root of the crank pin, with the break showing the characteristics of a progressive failure starting from a small crack. Last month, a connecting rod failed at the root of the stud where the two parts of the rod are joined, showing the same kind of failure. On both occasions, the resulting unrestrained motion of the piston broke the end out of the cylinder block.

Engine as it was when removed from car. Note position of piston and cylinder head.

Parts involved in the two failures.

Needless to say, these incidents severely curtailed my touring this season and removed a large part of the contents of my wallet. I suspect the initial cracks may have been caused by the amount of hard driving this car has seen; in 1999 it climbed Mt. Washington.

I completely tore down the engine and examined all highly stressed parts for evidence of over-stress. I used the dye penetration method using chemicals supplied in the Magnaflux "SpotCheck" kit. As the third picture shows, I found a suspicious crack.

Red line at root of stud indicates a crack. This connecting rod is not fit for use.

As engine failures in later Stanleys are not unusual, it is possible that all Stanley owners should check their engines for signs of incipient failure, particularly if they have had a hard test recently. The areas most likely to be a problem include the frame rods at the main bearing nuts, the crank web at the root of the crank pin, any point on the connecting rod where the cross section changes and the root of the piston rod at the crosshead.

Areas not likely to break but subject to significant wear are the conical wrist pin surfaces on both crosshead and connecting rod, the link blocks of the valve gear, all the pins of said gear and, especially, the valves and their seats in the block.

D. K Nergaard, 7 July 2001

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