What is the maximum timing I could be running on a 312 with Isky E4 cam? I have initial at 12* + 26* centrifugal for a total of 38* with about 15" vacuum at idle. I can get up to 18" vacuum at idle if I advance the timing to about 18-20*  and seems to run better but that bothers me running it that far advanced. It also has an adjustable vacuum canister that could be dialed in for maximum fuel economy. Where is a safe limit?   Dave

SE Wis

Frankly that's where I'm at too and my motor seems happiest there. I believe it is because the new gas is what it is an I'm currently going to leave it there. MIKE

Mike, still lovin his 57 t'bird after 53 years!

36 - 38 total by about 3000rpm is usually where they need to be.  Every engine is different.  Yours might like a little more or a little less coming in sooner or later.
If you run 18-20 initial, you need to decrease mechanical to around 18-20 to keep the max the same.



Lawrenceville, GA

Dave - Running with live manifold vacuum or a traditional Ford set-up?
I run live - with 10 initial 26 centrifugal - and 7 in the vacuum pot. Idle vacuum is 20 inches - with 17 degrees advance. This set-up tends to idle much cooler - and the 10 initial starts better than something higher.

 
 Steve Metzger       Tucson, Arizona

What isn't mentioned in this discussion is what grade of fuel is required to run 36 deg total, with 10 deg or more initial?


Paul

Steve   I'm running ported vacuum right now. I'll change to manifold vacuum and try it your way. Which way do I turn the vacuum cannister to decrease the amount of advance?  Dave

SE Wis

There are many variables to each engine and where you live and the type of fuel. I'm stuck in California and the fuel blend here is different then the rest of the US, and is crap as far as I'm concerned so I tune on the conservative side. My engine is a 292 with an E4 cam. I use manifold vacuum, 10 initial + 8 vacuum for 18 at idle. I'm only using 24 mechanical for a total of 34 at 3000 rpm. I use a small 390cfm carb. I'm happy with how it runs and with 3.89 gears and OD I average 18-19 mpg on hiway trips. Around town isn't so good but that is because of my heavy foot...

Dave - Sounds like you have the canister version where there is a hex socket-head screw down inside the distributor vacuum port? The hex is typically for a 3/32 hex key.- turning the screw clockwise unloads the spring (increases travel versus vacuum). So that would net increased advance. 
Turning the screw counter-clockwise has the reverse effect - reduces the travel at any given vacuum. You can play with it a bit by setting the initial up - then giving it vacuum(or not) and making adjustments to suit at high engine vacuum. My Olds makes lots of vacuum and I've used it as a "donor" before (with a considerable length of hose) saves fooling with any other T-bird adjustments while working on it.
On older distributors where the screw hasn't been touched in years - a good shot of PB blaster can help free it. If its stuck and you force it - the piston that loads the spring has very few threads, and it strips pretty easily. 

 
 Steve Metzger       Tucson, Arizona

Steve   The vacuum canister is new so I know it will turn. It will probably be a couple of days before I get a chance to work on the car. I'll post the results.   Thanks all.  Dave

SE Wis