Wow, that whole engine compartment looks like the car came off the showroom floor yesterday! That's neat, but you are kind of courting disaster with what look like original radiator and heater hoses — if they are, they're over half a century old. If you want to keep using them, run waterless coolant so they aren't subjected to pressure.

Back to the subject at hand:

The carb-to-intake gasket isn't the correct one; you're meant to have one 5/16" to 3/8" thick, not this thin one. But that's not causing the problem at hand. (Also, your choke thermostat is missing its cap, which'll cause some fuel waste, but this isn't causing the present problem, either).

The carb itself looks very nice on the outside, but that doesn't mean it works correctly. Still, from what you describe there's a good chance putting some settings to better values will fix the problem. Here's what I think is going on: retarded basic ignition timing (5° ATDC, in this case) dropped the idle speed, which then had to be boosted back up by turning the idle speed adjustment screw clockwise. That cracked open the throttle more than intended, which exposed the spark advance port to engine vacuum — if the throttle plate weren't opened so far, that port would be above it at idle, and so it would have little or no vacuum.

So, try this: with the engine warmed up and the transmission in Park, disconnect the vacuum advance hose at the distributor, and plug the hose (pencil or similar). Set the idle speed to about 750 rpm. Adjust the base timing to 5° BTDC. That will raise your idle speed, so back it down using the idle speed screw on the carburetor. Now reconnect the vacuum advance hose — if all's physically well with the carburetor, there should be minimal or no change in the idle speed when you do so. Now set the idle mixture as described in this post.

Now go drive the car and see how it does. Better acceleration behaviour? Any ping/spark knock? If there is, back the base timing off to 2.5° BTDC, again with the advance hose disconnected and plugged, after which you'll need to redo the idle speed adjustment.

Once those settings are happy, if you still get a stall on acceleration, shut off the engine, remove the air cleaner lid, and look down the carburetor throat while you open the throttle. Do you see a solid shot of gasoline every time you open the throttle? If so, your accelerator pump is working, but perhaps it is not configured or adjusted to give enough of a shot. This is affected by the bend of the link between the throttle lever and the nylon accelerator pump pivot on the passenger side of the carb, as well as which throttle lever hole that link is installed in, and the strength of the spring which drives the accelerator pump (that spring is inside the carb). For a fast diagnosis to see if inadequate pump shot is what's happening here, move the link to the outermost hole in the throttle lever — the one closest to the passenger side of the car — and see if the acceleration behaviour changes. If it does, and the driveability is now satisfactory, you can call it good or refer to the service manual (and/or the guides posted at the link above) for accel pump link adjustment.

If you do not see a solid shot of gasoline every time you open the throttle, the accelerator pump is faulty and the carb will have to come apart. Good quality rebuild kits are no longer generally available through normal auto parts supplies; get one from Jon Hardgrove at thecarburetorshop.com. While you are in there working on the carburetor, stretch the accel pump spring a bit to counteract age-related set.

When you install the proper base gasket (a Walker № G850 or equivalent; Hardgrove ought to have one for you even if you're not buying a whole rebuild kit), you may need to readjust your automatic transmission kickdown linkage and/or your choke thermostat — depending on whether these were adjusted to provide correct behaviour with the thin base gasket.

Beyond that, find tune-up parts and technique suggestions in this post.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks very much!

I agree about original hoses! I restored the car many years ago...all hoses were replaced with correctly marked new ones. They were done again recently.

Not sure what you mean by the choke thermostat missing the cap. I have a few of those NOS that are all the same

.

Again…many thanks….will review/work all your suggestions and report back.

Oh, whew, the hoses just look original.

Cap: there's meant to be a little metal disk where the choke pushrod exits the thermostat housing. It keeps the choke from cooling down faster than is wanted once the engine's warmed up and shut off.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Played with the car this afternoon and have an update.

I set the timing and the idle as suggested. Dramatic improvement. Didn’t get to go far, but the one thing I noticed was that there is a slight hesitation sometimes with light throttle application. Slightly heavier throttle application shows no hesitation. Car does not stall, or at least hasn’t yet. It used to stall often. Want to drive it a little more before I do anything else to make sure I’m on the right track.

For what it’s worth, currently at idle, it’s pulling about 5 inches of vacuum. No pinging noticed. I was actually surprised, I put my foot down a bit going up the hill from my garage and left a patch.

Can’t thank Dan enough for the help. Will keep you in the loop.

UPDATE: drove the car a little more. Still has stumble/hesitation in certain conditions. More odd, I came back after a good run and found the idle had gone up a little bit. Adjusted that. Doesn’t seem to idle as smooth as it did before. once the engine cools down, I’ll try to move the accelerator pump to the most outer hole.

I can report that now with or without the vacuum advance connected, at idle, the car remains at 5° before.

Glad to help out. 5" vacuum at the spark port is entirely normal — that's the minor amount which is why we disconnect/plug the advance hose when setting the base timing. Sounds like now it's just a matter of some fine-tuning. A combination of a bigger accelerator pump shot (to compensate for today's oxygenated gasoline) and following those linked tune-up suggestions (careful valve adjustment, better spark plugs, careful cap/rotor selection…) will get you all the way where you want to be.

Ordinarily I'd suggest going to a carefully-chosen electronic ignition system (HEI), but you might not want to add non-stock underhood components, given this car's unusually high originality. If that's the case, then pick out your components carefully; it is a lot harder to get good quality breaker points through normal sources of supply than it used to be. If you're sticking with points, stock up on well-made old-stock items; my pref is the Echlin CS-851 in old boxes (such as this.

But points-type ignitions start deteriorating the moment you start the engine after you install and gap them. If you want the considerable benefits of electronic ignition (driveability, performance, fuel economy, durability of tune) while retaining the stock underhood appearance, sneak a Pertronix Ignitor into the distributor, where it'll be fully hidden.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I’m sorry, Dan. I didn’t see your post before I updated my previous. Working on my phone has its disadvantages.

I had one of the early Pertronix units in this car. We went back to points to eliminate that as a problem. I understand the newer systems are better, and I would have no problem updating to that once we get the drivability fixed.

For what it’s worth, I don’t have the boxes in front of me, but I know they were Echlin parts. When I bought all those parts to switch back to points a while ago, they sold me the wrong rotor, but I didn’t realize it until the other day. I certainly can replace that.

If anyone is interested in seeing the car, I’m working on. Here’s a link to a YouTube video. https://youtu.be/TzwO2zvd2g0

Geeze, what a lovely car!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Holy crap, Matt, what an amazing job you did!

I'm sure someone has said this already, but that may be the only slant-six early seventies Scamp that is, or will ever be, restored to that level.

Absolutely amazing.

– Eric

Thanks very much for the kind words! Scamp truly was a labor of love for an old family member.

Okeh, proceed with the rest of the tune-up and valve adjustment per links provided, and see how that goes. Also keep in mind the Holley 1920 carburetor, especially the '70-'72 types, are not the world's happiest-behaved carburetors. I don't say you should give up yet — there are a lot of good resources and ideas here — but eventually there'll come a point when it's time to accept that old cars' driveability is neither as good nor as consistent as new cars' driveability.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.