Working on a 1970 340 Duster which is largely stock with the following exceptions; a Mopar Performance "Purple" cam shaft, MSD 6AL with a Blaster coil, Firecore plug wires, and a Mopar electronic conversion distributor with a vacuum advance. The plugs are one range colder than stock and gapped at .050 per the MSD instructions. Pump unleaded 92, 3.23 gears, 4 speed, stock tires.

What timing do you guys think would be best for this combo?

Small blocks can use less like 32-34 for starters and I would lower the plug gap to .035...............

(1) set the initial with the vac gauge method (2) shorten slots to get 35 total (& that is initial+slots with can capped) & the FBO plate is the easiest/cheapest way to alter slot length). (3) toss the heavy spring with the elongated loop on one end & sub in a mr gasket or MP light spring in its place (keep the OE light spring) for a start & you want a spring combo to keep you a bit under the pinging point at WOT up thru the gears on your hottest/driest (most likely to ping) day and to not start advancing any less than 1-200 below your hot in gear idle speed which is what the eng will see & be at at the stoplight (4) plug in the can & want to stay aways under the pinging point in everyday driving under varying RPM/speed/load conditions on your hottest/driest day and CCW with a 3/32 allen wrench will slow the curve (the amt at a given in hg it adds) but not the total. on both there is silent ping that you cant hear plus audible ping that you might not hear at a low level so give yourself a cushion & ANY pinging is extremely damaging. (5) check rotor phasing (6) reduce rotor tip to cap terminal clearance to .010-.015". NAPA has a rotor with a .060" longer tip for $8.xx Echlin # MO3000 or drill out the rivet on yor rotor & make your own to get the clearance exact. (6) add shims under lower collar to reduce axial clearance to .005" & speedway mtrs has flat shims with no bevel specifically for this for cheap. (7) add an external oiler with the flip cap like the 60's dists had (they are available) (8) peen lower shaft tang to reduce its rotational play in the intergear slot (9) add 1/2" ID collar on shaft with setscrew (Grainger has em) (10) tan cap with ribs (11) vent holes to eliminate ionized air inside the cap which can promote crossfire (like sitting under a tree during a thunderstorm can kill you cuz if lightning hits, it jumps to the ground in the ionized air straight down from the perimeter tips of the widest tree branches as opposed to conducting down in the main tree trunk (some does tho) but plenty enough is left to kill you

The stock combustion chamber seems to like 34 - 36 degrees at something like 3000 rpm. It's not a bigblock which wants 38.

I've decided to just set the plug gaps back to stock, stick the original cast iron dual point Prestolite back in it (found it in a box of parts that came with the car) and ditch the MSD stuff and electronic ignition. It doesn't need it since it's just a stock engine with a mild cam upgrade. Either way.

All the LA SB Mopars I've tested and raced like 30 to 32 total timing, high compression or blue printed stockers I know of others that thought there motors like more but once the top dead center was verified and coordinated with the timing cover TDC marks they ran the best with 32 to no more than 33 degrees total I know racers that saw 35 degrees when I saw 32 degrees on the same motor with the same timing lights on the same day one after another It is called paralax(SP?) errors