Search for "start of delivery". That should happen at 24 deg BTDC. I set to 27 BTDC in both my 300D's for improved performance & mileage, at the cost of slightly rougher idle, though can't say I noticed anything. Summary, you rotate the IP (at top) towards the engine block to advance timing. I think it would have to be pretty close to the factory setting since the stiff fuel tubes almost enforce that.

You remove the guts from #1 IP delivery valve (don't touch the 2 big nuts at the base which clamp the shim, they adjust fuel flow). As you pump the hand pump, fuel will come out until you rotate the crankshaft to 24 deg BTDC where the inlet port in the IP closes off to halt the pumped fuel flow. That is where "start of delivery" is. If you want to get fussy, you can rig up the little elbow tube shown in the manual and count drops (1 per sec is the spec). A bit unnecessary IMHO.

Did you pop test your new injectors? Should pop at 1950 psig +/-50 psi and give a uniform spray with no streamers, and shouldn't dribble until they pop.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans