Plugging Timed vacuum advance hose
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I completely respect your experience, here's where I'm at with my cars ...
383, xe268h (477/470), source heads, 9.44:1 comp, 727, 323 gear ... vacuum advance to full manifold, points distributor with pertronix ignitor2 : zero slow speed bucking, very smooth off idle throttle response, very smooth Hwy cruising, etc, etc ...
340, xe274h (488/491) eddy rpm heads, 10.5:1 comp, 4 spd, 3.55 gear ... vacuum advance to full manifold, mopar electronic distributor with jegs hi-rev 7200 ecu : smooth start into 1st gear, no bucking during parking lot driving, smooth hwy cruise, zero of your scenarios happening ....
Please explain why my cars drive so well .....
OK, well
1) they don't fit into any of the scenarios I offered
2) I already said I can't speak to autos
3) you may be a better tuner than me.
4) My scenarios are all at closed throttle.
Obviously, as soon as the throttle is opened, the vacuum falls and, with it, the low-speed vacuum-assisted timing.
How did you deal with the T-port sync?
But since you're here, can we talk about your stick car?
With those aluminum heads, and with that cam, your VP is down in the mid 130s, with cylinder pressure around 170, which;the 170 is pretty good,but IMO, 130s are a kindof soft bottom end and there is no way I would enjoy that with a 2.66x3.55=9.44 starter gear.What I mean is, a stock low compression 318 comes in at about 124, so your 340 is 136/124= just about 9.7% stronger, so it's no wonder she doesn't buck. And what I also mean is, I'm used to having mega-torque.
With the soft bottom, you can run almost any timing you can get out of the D, except of course the power-timing has to be limited.
Your combo wants at least 11.3 compression ratio, and so,with the cam in at 104;
Static compression ratio of 11.3:1.
Effective stroke is 2.59 inches.
Your dynamic compression ratio is 9.05:1 .
Your dynamic cranking pressure is 187.48 PSI.
V/P (Volume to Pressure Index) is 152...............................................................152
Your cam could even retarded , cuz 152 VP is a lot.
You could think of that 152VP as; 152/134=plus 13.4% more performance from idle to about 3600. Or 152/124=plus 22.6% over that low-C teener.
You could think of that as a higher stall converter, where the engine spools up to an rpm where there is 13.4% more torque.
Or you could sorta compare it to having 13.4% more low gear,or a 3.02, instead of the 2.66.
Or you could sorta-sorta compare it to having an engine 13.4% bigger in that low-rpm range,or 385 cubes.
Or you could think of it as the engine having a cam one size smaller,or so.
Read about VP here;
V/P Index Calculation
I ran this 11.3Scr, with a tight-Q, in my 367 on 87E10gas, for many years, at 32/34 power-timing.With a 367 my VP was over 160. This is a good bit more than and old 440Magnum (148VP), so you can imagine how that burns up the tires, er launches. But,this is where I spent many hours in the tune,getting the low-rpm timings,and the low-speed circuit,bugged out. In the end it was all worth it.
I run a 3.09 low in my box, also with 3.55s. But I run a GVOD, splitting gears when the occasion calls for it. With the VP over 160, I could easily run 3.23s. But with the 3.55s, I can use up all of first-over to hit 60@6380rpm, and 3.55s hit more other targets, so they're gonna stay........Jus saying.
What I mean by mega-torque, is; say you rev your engine out to whatever rpm gets you 170ftlbs, and then slip it out. Your low gear and rear-end will multiply that by 2.66 and 3.55 to get 1605 into the axles.That's a nice brisk take-off. In your current combo,this might be, I'm guessing, 2600rpm.
Now if you bumped the compression to where it makes the bigger VP, this rpm might drop to 2000rpm.
Now if you had a 3.09 low gear, this might drop to 1700.
Now if you had a 360, this might drop to 1600.Not to rag on the 340, just saying.
I had a similar cam (270/280/110) in my 367, and all I did was blip the throttle, to get some energy into the flywheel, and almost just dump the clutch,and power away. That's what I'm used to; dump it and go.
Please, I'm not ragging on your 340. I'm just showing what can be achieved with aluminum heads, and lotsa compression.
I guess I should also mention that IMO there is something going on in aluminum heads that I never expected. It seems to me that at low rpms and typical driving speeds, the aluminum must be sucking a ton of heat out of the chambers. This means total freedom from detonation in those usually problematic low rpms, under 3600, or so. But, as the rpm goes up, there doesn't seem to be enough time for the heads to get rid of the heat, and so the power rises faster than I would expect. At some point, the chamber temp stabilizes, and then the high compression turns her into an animal. That's my opinion. If there's a next time, I'm gonna juice it up with even more pressure, remember I'm still running 87E10, at 185 or better psi.
That's the best I can do.