Sexton R975-C1 a mess

[David Herbert]

LRDG,

If you go by part nos there is not much interchangability but a lot of that reflects improvements in materials and fits. The difference in pistons seems to be primarily about wrist pin retention. Crank I think is interchangable, C4 still has the redundant front oil pump mount in the front housing. Rings need to go with the piston. Cylinders bolt on but there are lots of bits on the outside that are different (air deflectors, throttle linkage, rocker covers, oil recovery pipes) Supercharger gears and impeller are different but not sure about the housing. It is about 20 years since I looked at this in detail but complete engines were fairly cheap then so I never needed to build a mongrel.

You are about to become an expert in all this I think.

David

[carl brown]

Your engine definitely failed due to a worn out crankshaft main bearing, resulting from no oil supply due to incorrect operation as David says.

You can fit a C1 crank in a C4 but not the other way round. The C4 crank isn't machined to take the C1 oil pump drive gear or lock ring.
Con Rods are the same in both engines but master rods different.
Pistons are basically the same but there are different rings depending on chrome or steel cylinders.
I can help you with parts if you can't find anything your side of the pond.
Carl

[David Herbert]

I definately bow to Carl's very much more recent experience with Sherman radials. As he is now involved I will keep quiet !

David

[LRDG]

Thanks for the good information. As mentioned above, when I become a retiree in April, I will be in a much better position to follow up on all these tips.

[Bob Phillips]

Not sure if I should weigh in here but..here goes..
Before you do anything else you need to strip that engine right down and see what you have to work with. If the case, crankshaft, gear case etc are rebuildable- all the rest of the parts are easy to obtain. You will need to really check for cracks and damage carefully. Second, while some parts between the C1 and C4 interchange, many do not. The crankshafts are different and use different bearing retention in the front, slightly different rear mains etc. Third there are many aircraft engines that have been flogged to people to use as spares- notably the post war R975 -46 which was a helicopter engine- though it looks a lot like a C4. It is an entirely different animal with few interchange parts. Be careful you don't get stung! Fourth, it is easy to destroy a C1 engine. I recall the overhauled engine in Bill Greggs Sexton having the bottom jugs damaged when safe start up procedures were not followed. Most of the many engines I have seen had bad main crankbearings- hardly surprising given the design and the design expectation that this would be an aircraft engine. Finally lots of parts and core engines are available right here. Tear that engine down and see what you need!

[Andrew]

Andy over at northeast military is selling off everything he has. He has parts listed for this over at www.site.ww2mv.com/Engines-Parts_For_Sale.html

Andy (not the above andy )

[LRDG]

Bob, the engine is coming apart as we speak - a complete teardown. The bottom of most the cylinder liners have been mushroomed out by the broken rods (red arrows) so it will take some time to get them out without damaging the case.

The rotating assembly is scrap, badly damaged. If I have it straight, the output spline damage shown would have been from the engine trying to stop the Sexton dead when it locked up.

The case may be OK. We'll check it with dye penetrant when apart.

I take your point about carefully checking we are buying usable parts.

Are the very thin, closely-spaced steel cylinder fins as-cast? If so, they are very high quality castings. Spin casting maybe?

Malcolm

DSC01193smallx.jpg DSC01120small.jpg

[Bob Phillips]

Malcolm- for whatever little bits its worth- those splayed out cylinder bottoms may be a pain to disassemble but maybe they will have saved the thin cast aluminium that makes up the crankcase. Later engines (eg the -46 helicopter) has much heavier castings in it. It also rated at 600 hp with much more blower and carb action. I cannot tell you about the fins, I always thought they were machined in but I don't know..Bob