Jamie,
I have never conducted a survey as I don't have enough engines nor time and energy to do it.
What I can say is that on engines in my possession, the centre bearing is (was) too high in relation to the front and rear mains.
Also, that the mounting structure conceived by Austin allows this to vary depending on how the nuts / studs are done up.
The proper engineering solution to this is to
a. divorce the C/M main fixings from the block studs.
b. make up a new centre main upper housing with undersize bore.
c. skim the joint face of the lower housing
d. then get it lined bored with the block bolted down in place
It's quite neatly explained in A7 mag 1985D
1985D.pdf (Size: 67.24 KB / Downloads: 70)
I don't consider it strictly necessary to make a new lower housing, but without a new upper line boring will achieve nothing (at best).
An engine prepared in such a manner can use standard shell bearings without shims and fiddles and can be reliable as long as your shaft is sound to begin with.
I have never conducted a survey as I don't have enough engines nor time and energy to do it.
What I can say is that on engines in my possession, the centre bearing is (was) too high in relation to the front and rear mains.
Also, that the mounting structure conceived by Austin allows this to vary depending on how the nuts / studs are done up.
The proper engineering solution to this is to
a. divorce the C/M main fixings from the block studs.
b. make up a new centre main upper housing with undersize bore.
c. skim the joint face of the lower housing
d. then get it lined bored with the block bolted down in place
It's quite neatly explained in A7 mag 1985D
1985D.pdf (Size: 67.24 KB / Downloads: 70)
I don't consider it strictly necessary to make a new lower housing, but without a new upper line boring will achieve nothing (at best).
An engine prepared in such a manner can use standard shell bearings without shims and fiddles and can be reliable as long as your shaft is sound to begin with.