Hey guys, I'll try a bit to contribute here. I waded into my 170 a couple years ago right when I got it, because it would drop off on light throttle, then right after that it would respond with a nice torquey pull. After pulling knowledge from this forum... man what a difference a few tweaks made right away! I did what seemed obvious to me first, including plugs and wires, and even rebuilding the carb (Autolite 1100). The car had sat a few years before I got it, so I was eager to do this. But it wasn't the cure. I came back to this forum, dug deeper, then down the rabbit hole I went. The gremlins I found on mine were as follows:
1. Needed a new accelerator pump diaphragm... mine had rotted and was leaking onto the motor with every pull. Couldn't see it right away, but the more I drove it, the more obvious it became. Even a tiny drip on acceleration means less fuel to the motor. The logic is obvious, but it wasn't obvious right away that it was even leaking. Of the entire carb rebuild, this made a difference, but didn't fix it...
2. Tightened up the linkage to the accelerator pump. I think you mentioned doing this. On mine, this closed the gap big time on the initial stall during acceleration. I did the drill bit set up, then found I needed to take it a bit further for best results. It didn't make it go away though, probably more of a bandaid.
3. Time by vacuum, check dwell. Timing by vacuum was a bit of a game changer... I found that the right timing for my motor was way out there as well. It was REALLY hard to get it to ping. I assumed some of this was because my balancer had rotated. It was old looking, easy to assume it was bad. Changing the balancer did nothing for me. The old one hadn't slipped afterall. Dwell was tricky because micro adjustments are difficult. The meter really is the trick... just keep trying till you nail it. All in all, these made improvement, but weren't the main problem.
4. Make sure your choke opens its blades ALL THE WAY when warm. These motors struggle to breath as it is. This also didn't fix the problem, but made overall performance better.
5. I suspected fuel pump and filter... mine were serviceable and terribly dirty, so I cleaned them with little improvement. Why I didn't do this earlier, I don't know. Though it should have been one of the first things, it also wasn't the answer I needed.
6. I was pulling excellent vacuum while timing with the vacuum gauge, so I assumed I had no vacuum leak. I could also watch the vacuum advance as I reved the motor. I finally grabbed the distributor vacuum advance hose and sucked on it (motor off of course)... it was a leaker. It should pull down tight, mine kept pulling. Don't draw to hard on this, they are delicate. As soon as I changed this, the car was amazing. I actually had to drop back a touch on the accelerator pump linkage to make it just right (turns out the drill bit adjustment technique was spot on). The stall at initial acceleration was GONE. Yet STILL the timing was out there on the balancer.
7. A friend came by and rotated the crank, watching the rotor. He'd rotate one way and then the other, watching for delay in rotor movement. Turns out it doesn't take much of a lag in movement to show you that there is slop in your timing set. I pulled the cover, finding SO MUCH SLOP in the chain. Rotate the crank enough to tighten the chain one side of the gears, then push the middle of the other side of the chain back and forth. It shouldn't move more than 1/2" (from what I was told). Mine moved 3/4". Everyone I've told that to was pretty amazed I hadn't slipped a tooth by now. Maybe I had, given how far off my timing was showing. I followed protocol for re-setting TDC (also found on this forum) and installed a new timing chain and gears. Now the thing times perfectly. Oddly, I didn't notice an improvement from this one. I think that lends credence to how accurate the vacuum method times your motor. It's the better way to get your motor (with its worn out components) to run at its absolute best. But I'm glad the chain isn't at risk for jumping a tooth now, and so happy to drive this car every day!
Anyway, maybe this helped... these really are fun peppy little motors once you get them in shape.
Final takeaway... this forum is amazing. FULL of wisdom that makes working on these motors a joy. Left on my own, I would have done less than half of the above, and wondered why my timing chain ended up breaking.
Good luck, and of course post back your answer when you find it.. .we'll all be better for it.
Cheers, Gruuvy.