Hi, new to the forum, sold my first x1/9 in 1983 and just got a bone stock 28000 mile 1980 carbureted X1/9 last month. I've been reading alot here and using the info, and in this case can contribute something, I hope.
So this isn't Fiat specific, but I built a few hundred distributors for 4 cylinder Datsun Roadsters over the years. On a non-emmission engine, speaking in crankshaft degrees, starting the advance at 900rpm and ending up with 32 to 34 degrees total advance at 3500 rpm was found to be the best all around, from bone stock 96hp pushrod 1.6 with SU's to big cam and big Solex sidedrafts on an OHC 2.0 making about 165hp. Vacuum advance distributors started at 16 deg base timing and 17 of mechanical advance, non vac advance up to 20 degrees initial and 15 degrees advance. As long as the advance is smooth and starts and stops in the right place, the middle area, 1500-2500rpm is not too sensitive. You can do 90% of the job with a good digital advance timing light with tach. Once you know how many degrees and beginning and ending RPM, you're ready to set your timing, or get it recurved So total timing (32-34) minus advance = initial timing.
Get the idle as low as possible and set/check initial timing. You can also set it the "safe" way. Bring the engine up above full advance rpm, say 4200rpm, set timing to 32-34 degrees using the advance timing light and tighten the distributor. Let it back to idle, and you're set. Either way you set it, check it doesn't exceed 35 degrees at full advance, a few degrees less gives some room for crappy gas.
And now you have a really cool timing light everyone will want to borrow.
Hope this helps
