Until I looked up the distributor specs on our '72 Newport Royal 400 2bbl, I had similar thoughts about the ignition timing on non-CA cars. But as with our 66 Newport 383 2bbl, the factory settings yielded right at 36 degrees BTDC timing, but at more like 4400rpm. With the '72 factory base timing being 7.5 degrees BTDC (plus or minus 2.5 degrees) and the '66 factory base timing being 12.5 degrees BTDC (which I upgraded to 15 degrees BTDC, as we were already using premium fuel in it).
I'm not sure specifically where the '73 timing is compared to the '72, but as I recall, most of the "emissions timing" was in the 2000rpm and lower area, rather than at 4500rpm. Which then means you need to get the lower rpm advance in sooner, but not increase the total. Unless the existing total is a few degrees less, which can be easily compensated for with the base timing setting. In any event, no more than 40 degrees total, although Nick usually uses close to 34 degrees, usually, on his dyno-run engines.
IF the itnake manifold has two holes in the bottom of the plenum, plug them up. That is "floor jet EGR". Or as the old-line Chrysler service manager at our local dealer used to call them, "Calibrated Vacuum Leaks" from the heat crossover passage. Although by 1973, you might have an external EGR valve. Getting rid of the EGR will make a very valid improvement in off-idle response, from my experiences. Which will make the car more fun to drive . . . when an off-idle slight punch yields "Let's GO" rather than "You want to do what??" from the engine.
As noted, the 400 is just an over-bored 383. With, of course, a new block casting to allow such. It was also a lighter-weight block that, as I recall, only allow something like a .040" overbore, if needed. Still, it is a strong block. The cam has a hair more duration, a hair more lift, and resultant overlap. Which means it is not that much different from the prior 383 cam (even the 383/325 cam). So that is good. So all of the good Chrysler "bones" are still there, just hindered by the rated 8.2CR compared to prior 9.2+CR.
IF you want to do something, then do a roller timing chain set. For "insurance purposes" against failure of the factory item (if you haven't already done so). Cloyes is a good brand for this.
With a 2.7 rear axle ratio, P225/75R-15 tires, and 4500 lbs, it can burn some rubber (no giant smokey burnouts without some help), plus raise the front end a bit on off-idle acceleration, but the car is more designed for comfortable and safe Interstate crusing AND also be competent on curving roadways, too. While getting reasonable fuel economy at the same time (just not in the 30mpg range).
Get the car tuned so that it runs reliably and eagerly, which can make the car more fun to drive. Resist ALL potential challengers on acceleration or similar . . . unless you want to upgrade to a late model OEM Chrysler 8-speed automatic. Just smile, wave, and let them speed off to look for another challenger they can beat. IF you think you might want to play "their game", look for an A-body with an LA stroker . . . something that will look stock production but with more power and torque AND a chassis that can use it effectively.
Just some thoughts,
CBODY67
