Torque convertor and detonation

[Bewy]

AJ, post #15. No, not race timing. Not at all.

Failing to use Man connected Vac Adv was an engineering error by Mopar. They didn't make many mistakes, but they did with this. GM cars used MVA. That means whatever timing the VA added was added to the initial timing & that was what the engine idled with.
Lower CR, more cam, single plane intake all need more idle timing. My 1966 GTO left the showroom with 26* of idle timing: 6* init + 20* MVA. It had 10.75 CR & a very short duration cam. A 9:1 engine with longer duration cam will need more timing.
The OP has already stated his engine liked more initial timing [ they all do when it is too low to start with ] & that is his engine sending HIM a message...
The LS engine with a modern, compact chamber, 10+ CR, idles @ 22* & only requires about 27* @ WOT.

 

[RustyRatRod]

I didn't see at what RPM all of the timing is in? If you mentioned it, I missed it. Sounds like maybe you just need more sprAng to slow the curve down.

 

[smokinnjokin]

Yeah I will put in a stiffer spring.
AJ, change of subject, but quick question for you. I tuned the carb using the methods you described and it runs very well, great transition off idle and good response through the rev range. It is an eddy 500cfm performer, #1403. If I want to swap on my 600cfm performer, and get it as close as possible before install, should I match up t-slot exposure beforehand? Anything else I should swap over or setting I should copy? Again, the 500 runs perfectly I am just leaving power on the table.

 

[AJ/FormS]

yes, but
I wouldn't be in big hurry to swap a known good-running carb for an unknown, onto an already detonation-prone engine with lo-stall TC, and 3.23s.
Your 500 is good to well over 5000rpm on your combo; how often will you go there?
Yes, I would set the T-slot and mixture screws AND float level, all the same

 

[Bewy]

You have to get the carb on the engine & get it running/idling to check the T slot. A large portion of the air for idling comes past the gap between the t/blades & t/bores. Machining tolerances, adjustment etc can change that & the gaps involved are very small. This will determine the final position of the t/blades.