My 1972 240z with 2 SU CARBS is still presenting sudden rpm drop when left at idle for more than 20 mins. I was advised that replacing the fuel rail with rubber hoses will solve this issue.
In conclusion, I still have not swapped the original Steel fuel rail that i have wrapped with heat reflective cloth. However, i did replaced a 170F Original Nissan Thermostat with 160F Stanton Thermostat to make the car run cooler. Left the car at idle after driving for 20 mins. Result: RPM started to drop randomly from 950 to 500 RPM tending to stall but never stalls. My father says that since i dont have the stock cam but a Schneider 274F Cam, the idle will never remain as stable on any traffic. Ill give you a Little more of details of what my car has:
L26 crank which makes my motor 79 mm stroke instead of the stock 73.7 mm
stock bore is 83 mm for the L24 and the L26 motors
my block has been bored out 1 mm to compensate for wear
that makes my motor a 2.627 liter motor, My E88 head from 1972 will give you about 8.7 to 1 compression.
Schneider 274F Camshaft, Pertronix electronic ignitor (no points), Pertronix 1.5 ohm flamethrower coil,
Airtex 8012S 4.0 to 4.5 psi electronic fuel pump. Its really pusing 4 to 4.5 psi.
Just give me your opinión on the random rpm drop at idle. I also notice that as the rpm drops the ahmeter drops from 45. I have a 60 amp alternator.