I agree with Henry. I have engine Dyno tested my tractor motor with a Mallory
dual point (with points that were used for a season) and a MSD box and they
both made the same power and torque.
I have not used a MSD box in the racer, but had a Crane 6000 (I think it was
6000 whatever...) ignition in 1998 and that was responsible for my only DNF
that year. Took it out and went back to the dual point and all is well.
I was using an Armtech Rev limiter until June this year. This is a small
electronic device with 3 wires that I got from TruChoice, but it only lasted
for 2 years. In June I was driving in the paddock at Lime Rock and the car
died. I found a broken wire from the coil to the dist., but the car still
would not start. Disconnected the rev limiter and it fired up. I have not
been able to reach the folks at Armtech to see if the broken lead caused the
unit to fail, but that is what I suspect. It is all sealed in epoxy, so I
can't take it apart to see. What was nice about this one is that you can set
it to whatever rev limit you want. No pills to mess with. Joe(B)
-- Henry Frye <henry@henryfrye.com> wrote:
I went full circle with the ignition in my TR4 racer, the car came with a
Mallory dual point. Thinking I would be better off with an electronic
ignition, I went through a pile of Lucas dizzies on my shelf and found my
best one, got a Crane XR700 and thought I would be jake. In a word, no.
High speed missing. The shaft was tight, the mechanical advance looked
great but spark scatter was awful.
The XR700 came with a shutter plate that fit the Mallory, so I pulled the
guts out of the Mallory and used the it to fire the XR700. Again, didn't
work well. It worked way better than the Lucas did, but still had that high
speed miss. I tried a couple of different coils, with and without a ballast
resistor, no joy.
So I reverted back to the dual point setup in the Mallory, and life is good
again.
The thing about MSD boxes seems to be not IF they will cause a DNF, but
WHEN will they cause the DNF. I never ran an MSD box, but just about
everyone I know that has run them has had trouble with them. At Grattan the
Snook's Dream Team Alfa cooked another one. Also, I have seen dyno proof
that they do not add anything to the TRactor motor power.
I understand why autocrossers need a rev limiter. In the 30 to 90 seconds
of bliss a typical autocross run lasts I never even think of looking at my
gauges. Maybe autocrossing will not heat an MSD up enough to be a problem,
but if I were building an autocrosser, I would look at other rev limiter
options.
Off to get wet at the Glen today.
Cheers
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