Hi tommyd, I read this thread with interest as I once thought of doing this myself. I'm not sure how the 140 dual system splits, but if it's like the 120 dual system the front/rear split on the system is ill concieved. If the front circuit fails you get rear brakes only which is the same as a emergency brake and almost useless for highspeed stopping, and if the rear fails who cares, the front wheels do 80-90% of the braking anyway. The 240 system correctly splits the two lines to both fronts and one rear each.
That being said, after scrounging in junk yards, buying unknown parts, and going through all the trouble of the mods etc there is NO WAY this will be cheaper in time and laboour than having two front calipers rebiult. Phone a brake rebuilder directly (yellow pages) and get a quote, when I did mine a few years ago it was $75 canadian each, and I didn't even try shopping around. For this price you get a guarenteed product and safe braking is
VERY IMPORTANT.
Tell your buddy the last place to save money is on brakes. It makes sense to nickel and dime lots of car stuff but never on brakes (besides it never works-Ibet if you manage to fit a dualmaster and matching calipers to a 120 at least one component will need to be rebuilt and in a flash you've hit $150...say $75 for parts $75 for repairs. And as always, time is money and the most important aphorism...BRAKES SAVE LIVES......(and cars)
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patrick of montreal, '66/120, '83/245.