I have a question for our experienced experts regarding early crank case interiors (in this case one from 1929).

The interior of this crankcase is very rough as one would expect from sand casting and it made it difficult to get clean for the engine rebuild. I want to clean up the surface inside to make it more difficult for engine dirt to get a purchase on the surface when in use and promote easier cleaning when oil is changed and the sump is off etc.

I know from my extensive experience with post war BMC engines that they used to paint the interior of the blocks with a gloss red oxide primer which was used to seal and smooth the surface of the cast iron blocks. I have used a product called "Glyptol" that is also used on electrical windings etc. with success in reapplying the paint after a block has come back from being cleaned and machined at the machine shop with the block now being totally bare cast iron.

So here is my question:
With the A7 crankcase being rough sand cast aluminum would it be an improvement to smooth the inside surfaces and paint it with this same type of gloss primer the way the later BMC engines were?

My concern is whether the primer would adhere properly and not come off in service.

Has anyone done this sort of thing themselves and if so did it work?

My goal is to try and promote and keep the engine interior as clean as possible making it easier for the dirt and byproducts of operation easier to drain out with oil changes. Your thoughts and responses are welcomed.

Thanks,
Stephen

My understanding is that paint was to capture the casting sand and maybe plug porosity. Sand is long gone from Sevens (if sand cast). There would seem to be a real risk of detachment of any paint, esp from on top of lacquer and carbon layers, and with traces of ethanol in the oil. Whatever the surface, build up from modern oils will be negligible. Classic oils which replicate the API SB and lesser oils of 60 and more years ago will produce a black varnish but it is very tenacious. With severe blow by can over a long time get an accumulation of sooty material on surfaces not washed with oil, but it does not move from there (ie valve chest).

Location: Auckland, NZ

I think you are concerning yourself unnecessarily about a problem that won't really exist with a properly built engine and regular oil changes. Get the case chemically cleaned to remove all traces of the old crud and carbon build up, use a modern oil, magnetic sump plug and stop worrying.

Location: Auckland NZ

I remember that the late Dave Flake of Quarry Engineering used to paint the inside of his new Ulster crankcases with red paint, maybe for the same reason.

Location: Stretham, Ely

Frost supply U.S. sourced red 'Glyptal' in the UK, expensive stuff though at £54.49 per US Quart (946ml)

http://www.frost.co.uk/glyptal-red-enamel-946ml-us-quart.html

Jeff.

Location: Almost but not quite, the far North East of England

I recently saw a crankcase that had a large letter painted on the outside with what appeared to be red primer. The proud owner, having exhausted all avenues over the years, now showed me his lovely clean bead blasted 'case...
No help to you except to demonstrate the tenacity of red lead.