40 degrees initial!

Hello, FABO. As you can tell by my avatar I'm normally over at the sister forum but I run a 340 in my 72 RR and figured there are more small block experts over here. I run my 340 now at 20* initial, 38* total all-in at 2400 rpm or so. Hughes 2832 cam .228@50 .530 lift. I wanted to see where she "wanted" the timing. I turned distributor to highest, smoothest idle. I was at 40 initial!! Lowered idle back to 850-900 (that's where I need idle) and kept going. Again, she was happiest at 40 initial. I don't run any vacuum advance (I only have manifold port on my AED 750DP and can't get rid of off-idle stumble with vacuum hooked up. I make 9hg at idle in gear. Tried many times. So vacuum advance may not be an option). I'm trying to avoid a locked down distributor (plus, hot starting I'm sure would be an issue at say 38 or 40 initial). Hot starting is no issue at all at 20* initial. Any suggestions to make motor its happiest with this situation? Thanks

Its most likely you are too lean at idle and transfer so you have to advance the timing to improve the fire events at idle to create enough vacuum. What do you have for IFR's and IAB's? You can partially block the IAB's with your fingers and see how it responds to a richer mixture at idle and on the T-slot as you bring the revs up while out of gear.

IMO you do not have enough compression with 160. I would aim for 185.