Differences Between A and B series Heads on the 110
If you are thinking of putting a cylinder head from one 110 engine onto another 110 cylinder block,
make sure you have the correct type of head.
The 110 engine went through A and B suffix incarnations.
Some of the design changes are well documented such as the increase in size of the main bearings,
but it may surprise you to know that the heads were also significantly different and not interchangeable.
Compare the photograph of the bare B series 110 head with the drawing of the A head from the parts catalogue.
You can see that the B head has a large web running down the middle between the rocker shaft mounting bosses,
which is completely absent on the A head. I don't know why this was added,
but it prevents oil from the far side of the web returning to the sump via the push rod holes.
To remedy this an extra oil return hole was added at the rear of the head,
and the block was suitably modified to incorporate a return passage to the sump.
The side of the block casting actually bulges out to accommodate this,
and the join is sealed with an O ring in a similar way to the water pump to head joint.
The mention of this O ring is the only indication that the workshop manual gives to suggest that things are different,
and nowhere is the B head illustrated!
B suffix 110 cylinder head
A suffix 110 cylinder head
Your comments...
Many thanks to Martin Hooper who e-mailed me to say that B suffix 95 engines also have the extra oil return hole,
which hitherto had been a mystery, since in other respects the heads are the same!
Also thanks to Steve Manwell in Massachusetts who e-mailed to say that he has experienced the same problem
when rebuilding his 3 litre MkII saloon.
It looks as if Rover, in an attempt to use the same block for all 3 engines, ended up having to re-design the
heads for all of them!
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