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IGNITION TIMING: Do NOT use the vacuum part of the dizzy. You just want one that idles at 10° and advances to 34° by 3000rpm, depending on your compression ratio. When you are checking ignition timing, see if both 1 & 4 give the same results. Vacuum advance is only of use if you have a super lean needle and a tiny A cam, OR a carburettor with a power valve.
EXHAUST SYSTEM: 1st, check to see if the guts of a muffler have not collaped internally, get someone to rev it up & down & see if the exhaust flow seem sufficent.
EXHAUST DESIGN: For K cam and twins SU's, D-Jet or K-Jet, use the stock twin downpipe arrangement. I recommend extending the 1.75" downpipes so that the length of 2-3 pipe attains 40" of length from the exhaust valve to the end & use the same style of 2-1 collector in mandrel bent form. Out of the collector, 2" pipe of 36" dumping in to a 2.5" pipe before the front muffler of 2.5", overaxle pipe of 2.5", then into the second muffler. The 2nd muffler could be 2.5" if you don't mind the volume, or smaller 2.25" or 2.125" muffler if you want it more quite. If you CBF'd with that, use the same exhaust system parts of a B20E/F car, which is 2.125". People forget that the part of the exhaust behind the twin downpipes is the collector, which is as important as the primaries & secondaries. The collector section needs to have a big area change to function, if using smaller, then feed the elongated secondaries in to B20E 2.125" quality parts & make the length from the end of the secondaries to the end of the tailpipe a multiple of 36" i.e. 2x, 4x, 8x 36" (1.8', 3', 6', 12', 24')
CAM TIMING: Set the valves to .018", wind it around to TDC and see if both valves on 1 or 4 are equally open, turn it around another 360° & check the opposite cylinder. If it's retarded, you are loosing power & torque everywhere and MPG goes down a little too. Ideally, you want 4° to 5° BTDC (aka advanced).
Almost forgot, make sure you have the correct springs in the SU's AND ATF or 5 weight oil in the dampers. Make sure the choke mechanism doesn't get stuck either!
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