If there is any horsepower gain from using this paint it must be minute...So little in fact it would have no relevance to any road engine...In the film he gives no comparative figures to either confirm the suggested problems or to quantify the potential gains...This may just be a case of which expert you choose to believe...(painted or not painted crankcases, smooth or rough inlet ports, increased internal clearance or polished flywheel rims etc. etc.)
Regarding the use of such paint in older bikes the only manufacturer that employed the practice routinely that I know of was Royal Enfield and my understanding was that it was a reaction to porosity issues with some castings...As an aside I recall Norton had a similar problem temporarily on later Commando cylinder heads...
Solving a problem that isn't proven to exist, or even to be self evidently a clear problem in a standard M20 or B33 engine for example, seems to be a rather fruitless excercise....Ian
In my late teens I was a cylinder head development engineering for a race engine company. Many historic race engines were painted red inside. The claim then was to stop sand being released from the castings. The owner of the company insisted that every trace should be removed. I can understand why, as some motor oils will lift paint.
Older machine tools are often painted red inside too. It does make them look better.
['Older machine tools are often painted red inside too. It does make them look better.']
The insides of the castings were painted on the automatic lathes and other machine tools that were manufactured by Brown and Sharpe when I did my apprenticeship with them...They chose yellow and it was just for the cosmetic effect...Sectioned engines and other assemblies often get the same treatment...
I considered painting the castings internally on my BSA engines at one point years back but didn't think it was really beneficial....I did repaint the crank cases on various Enfields I owned when rebuilding the engines back in the mid 70's as I was still able to source the paint originally used...Ian
After putting my crankcase in the ultrasound and puzzling over the results, I considered using silver paint to cover the staining patches on their outside surface.
I also remembered the effect that those WLA cases had all in red.
As I see it now, the BSA crankcases don’t require being painted in red lacquer. The porosity of the BSA castings doesn’t warrant doing it.
