[TR] overdrive usage

[January Williams]

Quoting Randall:

. . . The change was implemented in 1965 for the TR4A IRS . . .
The conversion back to a "banger" is discussed in Healey circles as a
"performance upgrade"; and many of the earlier "slurrer" units can easily be
converted back to "bangers".
Converting the other way is sometimes done as well, in cases where the bore
of the accumulator is damaged.  Probably a good idea as well, in cases where
an earlier A-type is being installed in a car with IRS.
===========

My IRS car came with an OD in a box, probably not the original, as it was a
22/61712 which would be from an early TR4. So when I had it rebuilt, I got
the smaller accumulator piston / spring from Moss which effectively
converted it to a 22/61753 appropriate to the IRS.  I kept the original
piston and spring so the unit could be returned to original. (cf
"performance upgrade")

The smaller accumulator caused the operating pressure to drop quickly and
then recover, to "soften the engagement" (quoting from Nelson Riedel's
excellent series of articles) avoiding possible damage to the (IRS) joints.

As to operating, I always tap the clutch and slack the throttle when
engaging the OD, but not when switching it off . . . but I'm usually
meandering, not power commuting, I want it to last. After 10 years it took
longer and longer to engage and then quit a couple of weeks ago, so I had to
pull out the seats and the tunnel and reset the operating lever with the
3/16 drill bit routine; works great again. I did spill blood again though,
scratched knuckle, seems like every time, is it Vucan that's the god of
mechanics?

Cheers
January Williams
66 TR4A CTC74217 LO  Salem, Oregon