Single Cylinder Crankcases

[tony.barnett]

I have a 1951 VH engine (prefix RB, which is 1951) with some damage to the crankcases. I also have a set of VB crankcases (prefix MC, which is 1956). Is there any reason why I couldn't use the VB crankcases for the VH engine?

The main difference I can see is the RB cases are 4 base studs, the MC ones are 5.

[pete.collings]

No reason, you just need to drill and tap a hole to take the fifth barrel base stud. It might also be worth checking if the large d/s and t/s bearings have moved in the crankcase, as these will (should?)be replaced by roller bearing outer races, and the d/s outer can come loose and work inwards, catching the big end nut.
A bit of locktite should help if this is the case.

[tony.barnett]

Thanks Pete. I'll be using the 5 stud cases with a four stud barrel. So just blank the fifth stud (between the pushrods)?

[john.nash]

I just been down club night with Len, Dick and the boys.

This subject came up as I have a set of '47 VB cases, and sets of 52 and 57 VH cases.
I also have two VB crankshafts and the crankshafts to match the VH's.

I was told that the cases are all interchangeable, apart form the 5th hole on the VB and later VH cases. Which as Pete says, can get a bolt through to seal it when using the VH barrel with separate pushrod tubes. I already have an OHV top end on a VB bottom end, with separate pushrod tubes. The extra hole is covered by the compression plate, in this instance.

My crankshafts on the otherhand, apart from the obvious conrod differences between VH and VB will have different crankpins, big ends and flywheels. Mainshafts are interchangeable though.

I have learned sooooo much in a year. blimey.

[ben.mitchell]

Tony
The fifth cylinder base hole on the VB cases is not a base stud hole but rather a tappet chest oil drain so it does not have a thread tapped in it...in which case if you want to seal it with a bit of stud ..then you will first have to tap the thread! I did once convert a VB crank case to a 5 stud VH crank case use and if my memory serves me correxctly I found tha the drain hole was not in the same location as required for the fifth stud VH use so I had to get it welded up and then drill/tap a new hole....the correct cylinder base gasket makes a good template for this!
Ben