Red Jupiter Cylinder Heads

[Mike Allfrey]

I note that on the front cover of By Jupiter!, just arrived, there is a photo of cylinder heads painted red. I am wondering why the cylinder head gasket surfaces have been painted red as well?

I remember, back in the late 1950s, a local garage was overhauling an Austin 7 engine. During the assembly process, all gasket surfaces were brush painted with common silver paint and allowed to dry prior to installing gaskets. This also applied to the cylinder head and the exhaust manifold flanges.

The reasoning was not explained to me, but I was about to try the same on my profusely oil leaking Royal Enfield 350 c.c. Bullet, but before getting to that job, I obtained an oil-tight BSA A7 500 c.c. twin.

So, is there a good reason for painting the head gasket surfaces with high temperature red paint?

Keep well,

Mike A.

[Keith Clements]

The last engine I put together was coated in all the waterways by red paint which I assume was done to reduce corrosion, but it may have been a coating to mitigate porosity.

[Mike Allfrey]

Thanks Keith,

In the farm machinery industry it was common to paint the insides of castings with what we called 'red lead' paint, mostly to prevent oil leakage from within. That coating was applied before any machining was carried out for such as gasket joint faces and bearing bores. At New Holland we used a particularly good paint, but that sort of fell apart when lead containing paint was banned here.

I have not seen the practice used in engine coolant jackets, probably because the paint had insulating properties and could flake and clog radiator cores.

The silver paint must have been used as a form of sealant. The man rebuilding the A7 engine had owned and operated the village garage since about 1920. He forged a new connecting rod for my moped from a Ford Model T half-shaft. that one did not break! So, he knew what he was doing in his workshop.

Stay well,

Mike A.