[Healeys] DW overdrive piston

[Bob Spidell]

Note Laycock went from steel rings to O-rings on the actuating pistons 
on the later cars. Went I overhauled my BJ8's O/D at about 205K miles 
the O-rings were in good shape, except for the wear you'd expect on the 
cylinder wall side (flat-sided).


On 8/3/2022 9:20 AM, Michael Salter wrote:
> I have a question about the "O" ring type of accumulator.
> The way the accumulator works is that when it is fully charged the 
> piston moves against the spring until the rings reach the radial holes 
> in the wall of the housing which acts to relieve any excess pressure.
> My concern is that at 3 - 400 p.s.i. oil will obviously get behind the 
> "O" ring and force the material of the "O" ring into those radial 
> holes and then, as the piston moves back over them, a piece of the 
> ring will shear off.
> I'm guessing that Laycock-DeNormanville used the complex cast iron 
> rings rather than "O" rings because they recognized the possibility of 
> this happening.
> I'm sure that tiny pieces of the "O" ring would be found in the filter 
> if this was a problem. Anyone found them or noticed damage to their 
> accumulator "O" ring upon disassembly?
>
> M
>
>
> On Wed, Aug 3, 2022 at 9:08 AM Bob Spidell <bspidell at comcast.net> wrote:
>
>     I put one in my BJ8's O/D. It's subjective*--O/Ds seem to work a
>     little
>     quicker with cold, thick oil than hot oil--but it cuts maybe a
>     third off
>     engagement time on average. I had the O/D on the bench and
>     disassembled,
>     and the current one had a scored barrel so, why not? Engagement isn't
>     much, if any, harsher than before which, I believe is the reason DMH
>     wanted the weaker, smaller spring. If I'd known about it, I might
>     have
>     bought AHSpares' with an O-ring instead.
>
>     * I've never really 'timed' O/D functioning, it would be a bit
>     awkward;
>     anyone done it? I usually tap the clutch pedal when engaging O/D, and
>     give a little throttle when disengaging. I thought mine engaged a
>     little
>     quicker when I switched to synthetic fluid from engine oil, but in
>     all
>     cases confirmation bias may be involved.
>
>
>
>     On 8/2/2022 8:09 PM, Joseph Costa wrote:
>     > Has anyone installed their upgraded overdrive piston?  If so, is it
>     > worth the trouble ?
>     >
>     > Joe
>     > BN1 #923
>     >
>
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