Srm timing side big bush conversion

[Will]

Hi just stripping my engine down and removed bush it has to much play , funny thing is measuring up crank it's 1.49 od ringing round no one does this size my crank appears to be to big , the big ends are standard a friend has told me he remembers srm doing a big bush conversion alongside the bearing conversion in early days ?????? anyone else remember this here are couple of pics of present bush

[muskrat]

That's an A65 size -0.010". A10 is 1.375".
The PO either modified a A65 crank or sleeved the A10 crank.
Cheers

[Will]

Ahh what size do the a65 come in the crank hasn't got sleeve , but the bush doesn't have the steel sleeve as normal , did the a65 come with small  big end journals 👍

[RichardL]

measuring up crank it's 1.49 od ringing round

I'm not quite sure what you mean by the expression "ringing round". If you mean that, by measuring with a micrometer, the timing-side journal is 1.490" in diameter, then it's right around 0.009" undersized for an A65. That's too big for an A10, so, we must assume the journal has been ground down and the bushing replaced and reamed. An engine with 0.009" timing-side bush clearance would die pretty quick, I think.The tape measure in the picture isn't really infomative.

the big ends are standard

Did you measure the big ends with a micrometer? Standard for the A65, and later A10s, would be 1.687".

Richard L.

[a101960]

I'm not quite sure what you mean by the expression "ringing round".

I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

[Will]

I'm not quite sure what you mean by the expression "ringing round".

I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

That's right a101960 , I measured with digital vernier not perfect but good enough the machinist will be more accurate

[RichardL]

I'm not quite sure what you mean by the expression "ringing round".

I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

I guess I was confused by Will's economical use of  punctuation.

Richard L

[Will]

I'm not quite sure what you mean by the expression "ringing round".

I think that you will find that expression means telephoning various suppliers to enquire what sizes they have in stock.

I guess I was confused by Will's econimical use of  punctuation.

Richard L

It's been said before Richard 👍

[muskrat]

Now to add more confusion. OK that's the bush (std A65), now what's the size of the crank main journal?
Cheers

[Will]

Now to add more confusion. OK that's the bush (std A65), now what's the size of the crank main journal?
Cheers

Main timing side 1.49   crank is small journal std shells ?? I have found info about srm doing a similar conversion before they did the needle bearing conversion , a friend has a old srm catalogue with a description in it

[muskrat]

So the crank main journal must either be sleeved or built up with weld and ground back.
See if you can get a copy off your mate. I'd be very interested to see how it's done.
Cheers

[Will]

Hi just heard back from srm it was a conversion they offered when they were based in Cardiff , the crank was sleeved then machined and a bush made to spec , they have said they will make a bush up for me , I will try and copy the info and post on here 👍

[muskrat]

Thanks Will. I wonder why they did that. I can't see that by sleeving the journal it would be any stronger (still relying on the parent metal and radii). Building up with weld and grinding back would be a bit stronger but I'd be worried about what the heat would do. But then all of my crank breakages have been at the crankpin  .
Cheers

[duTch]

 

...I wonder why they did that....

My two bobs worth is it gives a greater surface area to bear on

[Will]

Hi Muskrat took some pics today you will have to enlarge it to read or I can email you pics 👍