Kenyon wrote:
> When installing the plumbing for a dual MC on my originally
> single MC car, do I:
>
> Run 1 line to both front wheels and 1 to the rear?
>
> <<OR>>
>
> Run the lines like an X with 1 line to RF/LR & 1 line to
> LF/RR wheels?
>
> I am assuming that the first is correct.
>
>
> Should I get a proportioning valve if I do the front/rear
> deal?
Kenyon, in reply, I am most ways through this project. The controlling
element in the equation is what kind of new master cylinder are you going to
get. On the one we chose, from a 1969 Dodge Charger, there are two separate
pots. In order to use a proportioning valve, you would have both lines
going to a junction box of some kind. In essence you have a single line
system, as now, but with a back up pot should anything go wrong with the
main one. I like this set up as it is probably the MC which is most likely
to fail, or at least it has been in my experience.
However, this is not what we are doing with my 1958. We are running two
lines independently of each other. One line goes to the front brakes, the
other, connected to the front pot, goes to the rear. Any proportioning will
be done by the MC itself. The pot nearest the fire wall is smaller and the
lines attached to it are smaller in diameter than those going to the rear.
The theory is that the front brakes, responsible for 70%, or thereabouts, of
stopping will get applied fractionally sooner and with slightly higher
pressure. I am not sure if this, in fact, going to work. It makes sense,
except we have had the hardest time getting both the front and rear brakes
up to appropriate pressure at the same time. This was because a rear wheel
cylinder had a very minor leak. The project stalled when my hands got
burned a week or so ago, working on another car, so I am unable to report
back on how things turned out. As they say, stay tuned for further
messages.
I am becoming quite leery of the new set up simply because, without the rear
brake line attached and its aperture on the MC blocked, we have achieved
phenomenal braking on the front wheels. However, if a small leak in a rear
wheel cylinder can prevent pressure being achieved on the front at all,
what's to stop that from happening again, if another leak occurs? That must
mean there is some kind of link between the two pots. This becomes even
more complicated when you consider the dual line to a block with a
proportioning valve. If one pot goes out, what will stop both pots being
affected. My colleague in this endeavor, assures me that once we have full
pressure on both the front and rear brakes at the same time, should one line
fail, the other will still maintain pressure. I live in hope, literally,
that he is correct.
Hugh
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