Davis diesel head improvement

Don't forget plumbing shop O-rings, as the standard rings last much longer than the original McCoy soft rubber rings. I've been using them in my McCoy .049 diesels for years. Mine use the size 10 rings which are an easy stretch over the McCoy contra pistons, but snap right into the groove, seal very well, and last a long time.

I bought my first McCoy .049 diesel in 1953, and I don't remember seeing O-rings used on any US diesel engines before then. The rings used were soft white rubber and shredded in just a few runs, so the head and contra piston had to be removed regularly to flush out the mush. I called McCoy to order more rings, but they insisted they would send me some just for the asking. The bag they sent lasted far longer than the engine was in my possession.

Bought several McCoy .049 diesels in later years, and haven't worn out any plumbing rings yet.

One precaution I would recommend for any diesel engine, is using care when installing the contra and new ring, so the ring is not damaged during installation.

Bill