Sloper info

[Mike Farmer]

 

My engine No is Y8--1250. What is it.

Are the inlet and exhaust valves the same. If not whats the difference in general terms. Bigger, smaller, longer etc

Mike

[JulianS]

Engine is a 557cc H31-8 side valve model from late 1931. This model was much used by the Post Office.

[Mike Farmer]

 

Hi Julian.

Thanks again for that. But--this is an OHV engine.

Mike

[JulianS]

You have a mystery engine!

Y8 prefix definately for the H31-8 according to BSA.

[mark quinney]

 Hi Mike
Assuming the 500cc is  similar in construction  to the 550 , on the overhead valve engines  if you screw the  valve tappet guides into the crankcases they slope in towards each other on the side valve they are vertical so this could perhaps tell you if you have a side valve crankcases  . I tried to find out awhile back if you can fit overhead valve head etc  onto side valve cases some said you could some said you couldn't but no one really seemed to know for sure if your engine was running before you got it then yes it must be able to be done . I only found out about the slope of the tappet guide  by having two different sets of crankcases on the bench at the same time hope this helps regards Mark

[Mike Farmer]

 

Hi Julian.. I never doubted the veracity of your information and indeed am simply surprised. So we shall try to delve more deeply into the mystery.

Hi Mark, after reading post from Julian I was beginning to think along the same lines. I have no idea if or when it was last running, but when it was purchased it was in "one piece" so I guess that it must have run. We shall find out eventually. I shall keep you in the loop as things progress.

Mike

[Mike Farmer]

 

If anyone can assist I would like to know if the conrods are the same for both motors.

This "mystery" would probably begin to explain why the crankshaft is mis-alligned. Someone has probably stripped it to change the conrods and done a bad job of reassembly.

Whatever---it certainly shows signs of having run. Of course another possibility is that someone has shoved an OHV motor in and re-stamped the number. How naughty?.

So there we go gents any light you can maybe throw on this will be gratefully accepted.

By the way chevvy big bore valves are 1.72" across the face and I believe that sloper is 1.75". Thats a difference of 030".

More eventually

Mike

[Mike Farmer]

 

OK , the thick plottens. Just checked this out and the tappet guides definitely slope in toward each other, Thus the cases appears to be OHV. About the Engine Number---No idea. It all points to being OHV so my guess at the mo is that someone(maybe the post office) restamped the engine--this No appears to have been PO. I understand that it was not unheard of for this to be done with replacement engines and indeed frames.

So back seeking advice???/

Mike

[JulianS]

Mike

Can you see any casting numbers on the rod, cases,  covers etc?

Julian

[Mike Farmer]

 

Hi Julian. Must confess have not looked very deeply at the mo but I know that there is a No on the crankshaft. Will do a more thorough inspect later in the week.

Ever so confused. comic.

Mike

[Mike Farmer]

 

:)Hi Agen Julian

I have found the following numbers on the motor.
on the flywheel(crank) 24-821 and ?4-821. I assume that they are both the same. Nothing at all on the conrod.

On timing side? casing 24-1276. also on opposite casing apparently ----4122 or 4L22

On cylinder barrel  1712 or 1312. No prefix numbers.

And that is that.

Mike

[JulianS]

Mike

I think you timing side crankcase half casting is a 1932 part. The part number in the book is for the casting with fixed fittings. These numbers usually one different to the casting number. Cant make anything of the other numbers.

The H32- 9 SV part is 24 1277.

The S32 - 8 OHV part is 24 1275.

Both these had 3/4 inch gudgeon pins while the H31-8 had a 5/8 pin - according to the Hepolite catalogue.

The H31-8 was being sent out from the factory as late as June 1932.

Not sure if this takes the mystery any further forward.

[mark quinney]

 Hi Mike
Looked at my crank and the numbers on the flywheels are24–321 is it possible you've missed read the 8 for a 3 , they're out of a 1930 overhead valve
Conrod as the number 24–281 on it and as Julian says it should be a three quarter inch gudgeon pin . The conrod measures 23.5 cm  but could only measure that with a tape measure
In my parts book for 1930 and for 1931 The flywheels are the same part number for the overhead valve models for both years
There is a different part number for the flywheels for the side valve
there are 2 x 4 digit numbers on the crankcases just above the oil fill they are the same number on both of my cases and I'm assuming it's for them being a matching pair of cases
There are no numbers on the barrel
My valves also measure 1.75 inches
Hope this helps
Mark

[Mike Farmer]

 

Hi Agen..

Anything is likely. I will look again at all these No's and see if I have mis read them. N]and measure the gudgeon pin. We appear to be getting somewhere even if not very fast. No sweat.

Mike

[mark quinney]

Hi Mike
I had a bit of a daft idea but thought I'd try it so went in garage  where I've got 1930  side valve and 1930 OHV cases so tried putting them together , when pushed together  the OHV timing side and side valve drive / engine number side don't quiet join up tight at rear of engine but are very close and would take very little work to make them join correctly  . The front end does join up and all bolt holes appear to line up the only obvious sign of them being wrong was a difference in the shape of the castings under the magneto mounting plate  . When I joined the side valve timing side case to the OHV drive / engine number side they fitted fine again casting differences under the mag plate .
So it could be possible that in the past someone has joined a side valve  drive side case with the side valve numbers on it to an overhead valve timing chest side I only spent 15 mins on it and  I could be wrong but it may help explain your dilemma .
So does anyone know if this is possible?
Mark