Fun with troubleshooting leanness (and 5th gear cruising temps) Options

[emerygt350]

So I have been playing with adding resistance to the cht to bump my mixture. Messing with the mps was not getting me to where I wanted to be I wanted something a little more global. Anyway, bought a 10 dollar Bluetooth relay. Set it up so one channel was clean the other had 50ohms resistance in it. As I am driving I can switch back and forth and watch the results on the cht and AFR. 50 is really working well (this is all in addition to my 250ohm found on 73s). Now I have added another 20 ohms to the alternate so the relay will switch between 50 and 70. It ain't pretty but it's only for troubleshooting.

[DRPHIL914]

hey there , am following your testing on ths and curious about your results, because i have a similar issue and similar set up. my rebuild is also using a similar cam, d-jet, a 123ignition distributor, and also the motor seems to really run well with more advance and the 93 octane. i think i am at 30 degrees advance at 3400rpm(set using stock recommended method.) and wondered well if i back off to the stock advance in timing, this would probably help head temps but if i remember when i put that in a couple years ago, it hurt performance but didnthelp head temps that much. I run no vac or retard hoses on the dizzy, i could never get a good proper rpm at idle set up like that.

i also have a bored out throttle body bored to 50mm, stock air cleaner.
compression is 9.5, these are new heads new P&C's, etc, SSHE and SS muffler from Ben.
i bumped my fuel pressure up to 32, it likes that, and my A/F readings are really good, but still on highway cruising at 75mph i am at about 3400-3500 rpm i think and get great milage and the A/F says 13.5,oil temps perfect but head temps will go slowly up and get up around 330-350 and if i am pusshing up a hill or something then they go up more,
I added a rheostat to my CHT and settled to around 1000 ohms, - all temps are fine otherwise, and i felt like maybe this is due tojust not enough airflow over the #3 head,
i wonder if they have this issue with the set up they are developing at PMB for this same motor configuration.
BTW if i cruise in 4th gear at about 3400rpm head temps drop to just under 300, that isa bout 60-65mph give or take, so why? less heat production?

i like to take longer drives but cant cruise on the interstate witough watching my head temps and worrying about seeing that read out of the AFR being around 340-350.

Phil