258 / 4.0 Head / 260H Cam

Heavy 488 wrote: Yeah, costs a few $ up front but not all that bad when you consider how much time spent that you'll never get back from trying to wrestle the pig to the floor. I put one in my daily driver (injected). If I don't see 14.7 rolling or 12.8 working it, I know theres a problem.

I feel like there should be more than 11"-13" of manifold vacuum, even with the 260H cam. Maybe something more on the order of 16"-18"? Does anyone else around here run that cam that can chime in on what kind of vacuum reading they see? 

I have the dual plane, I'm not sure if that makes a difference.  In any case, I replaced the jets with the factory spec defaults and it is running pretty good now.

tomj wrote: Vacuum spark advance really helps with fuel mileage, but it confounds tuning. You might try plugging the hose, running no vacuum advance initially. THe downside is it will hurt your highway light-cruise mileage.  "Too many variables" makes diagnosis hard.  YOu want vacc adv, for sure, but later. FOr now, run without. See if you can separate symptoms and behaviors. For no reason I can articulate, I suspect a carb issue. So... is this a too-big carb? Bad accellerator pump issue? What if you sloooowly crack the throttle, does it accell OK? Repeat until you are CERTAIN its behaving right. Then try a "controlled' punch-throttle. cruise 30 mph in 2nd, whatever, press throttle. Does it do the right thing? Stumble? Bog? I have no reason to think any of those things are the issue, but being methodical helps navigate the jungle.

"most engines" - and it varies "somewhat" depending on stroke, rod length and other factors, but most should see peak combustion pressures at about 14-16 degrees ATDC. My college texts and papers say 14, I've seen some say as late as 16. 
So whatever timing works to achieve that - because BURNING (and this is a controlled burn, not an "explosion" as people keep calling it) burning takes TIME. Higher RPM means less TIME to burn, since you want peak pressures at about 14 ATDC, you have to start the process sooner to be finished in time. 
Typically, total advance, everything all in - about 36 degrees total at 3,000 or so RPM. 
Sounds like you could be close to that - assuming the mechanical advance isn't yet all in at 2400 RPM. 
My 360's HP peaked out with a total advance of 38. I could see in the dyno sheets that they started with 36 degrees total and then later bumped up to 38 and saw more HP and torque - but if you achieve peak combustion too soon, you LOSE power. so those who say you need more timing - well, won't say what I may think of that because more timing can FIGHT you - you get too much pressure at the wrong time - even before the piston is all the way up to TDC, or even when it's just past TDC and has no mechanical advantage over the crankshaft. 
Think about cranking on a Model T - where do you have the best advantage to spin that engine using the crank on the front? With the crank at 12:00? 6:00? OR, is it somewhere closer to 12:10 or 6:37?