Honda CB750 Sandcast

sandcast head paint internal

UK Pete

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Just blasted my head, i noticed the inside of head has same silver paint as external, could this be for the same reason as the crankcases, ie the possibility of being porous, is it worth painting the inside to seal it up, has anyone else done the same or ever wondered why it was painted
pete


4pots1969

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Pete,
Let well alone..
I think sincerely that to paint the inside of crankcases serves strictly has nothing, and if one day it turned out that they are porous what I doubt strongly, we would have since all died since a very very long time...
There is in more the very big risk than it damages the engine if small particles of paint get loose and block the circuit of oil..
On the other hand I made the decision to make small holes in every tubes of the frame to inject a very powerful rust inhibitor to block the rust definitively,  I think that it was necessary to make him because the tubes of the frame corrode by the inside.
Gerard
« Last Edit: December 17, 2014, 06:44:51 pm by 4pots1969 »


Sam

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I painted the inside of my engine with glyptol on Vic World's advice. Honda had their own paint back in the day!
Ujeni Motors
Sandcast #410
Sandcast #538 Watch the restoration!
Sandcast #6592 All original daily driver.
Diecast #16608


4pots1969

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It is great!! But that serves has nothing..
For an crankcases in Cast iron Yes.. But not for an aluminum engine.!!
« Last Edit: December 17, 2014, 07:09:23 pm by 4pots1969 »


Sam

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From what I have read, glyptol does a lot! It seals the inside of the engine against the possibility of pores at least...better than that, it promotes quicker movement of oil. Take a look at the surface of the inside of the engine: very bumpy! The gyptol smooths that out resulting in a higher performing engine. Im told Honda used something similar back in the day.
Ujeni Motors
Sandcast #410
Sandcast #538 Watch the restoration!
Sandcast #6592 All original daily driver.
Diecast #16608


UK Pete

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It is the cylinder head internal that i refer to it looks like they spray the head then do the machining afterwards leaving paint on the inside
pete


4pots1969

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Ujeni,
I agree with you that Glyptol improves the circulation of the oil, but there we not speak of an engine of competition with of very high-performance and alloys for the foundry of these aluminum engine is of excellent quality, fragile and breakable but certainly not porous and you will notice that there is no budding of the aluminum in surfaces even on the engines which were stored and abandoned outside in the rain for years and years and that it is good the sign that the aluminum of these engine is not porous..
On the other hand, during the restoration of crankcases, it is necessary to clean them but especially not to clean them completely inside and it is necessary to keep this yellowish patina trained by the oil and the time which protects the aluminum.
Personally I would not take the risk of making paint has the inside of the engine which can disintegrate at any time on certain places even if Vic World recommends him..
Then, you make as you think best!! ;)
« Last Edit: December 18, 2014, 09:07:43 am by 4pots1969 »