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S50 Cylinder Casting

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Richard Bailey 225/10/2020 16:39:56
1 forum posts

Hi All

I've just started work on a Stuart S50 as a first project. All going well so far, nearly had a cylinder boring disaster but managed to save it thankfully and ended up with a decent bore but that's a story for another time!

Now I have the bore sorted I was looking to tackle port face next but I think I might have a bit of an issue with the casting. The actual features of the ports seem to be really deeply recessed below the cast face. I need to take about 3/64 off the face to get to the finished dimension but the cast port features are at least 1/16th below the surface. Looking at photos from other builds all the ports seem to be nearly level with the cast surface.

As far as I can see I have two options;

1/ t's a casting fault and it might be replaced.

2/ Machine off enough material to get a good port face and increase the finished valve chest thickness to compensate. I think I would just have enough material in the casting to make this work and keep the relative spacing between the piston & valve rods.

I couldn't find anyone else that had a similar issue so I'm not sure if this is a common thing or if it really is a casting issue, I was just wondering if anyone had seen anything like this before. Other than this the casting seems to be free of the more common issues.

Kind Regards


David George 126/10/2020 07:28:52
1381 forum posts
448 photos

Hi Richard I havn't made this model but I think you have answered your own question as you have invested time in the cylinder bore and there is sufficient material on the valve chest, personally I would clean up the casting to a working situation. Although maybe someone may suggest an intermediate plate or just sending it back for replacement.


mechman4826/10/2020 14:49:40
2789 forum posts
431 photos

I would go for # 2 as the easiest route. My S50 had similar issues with the valve chest; one side is thicker than the other by, IIRC 1/32 - .030" it looks odd/ offset but that is the finished dimensions, the thinner side goes to the port face so watch out for that.


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