Page 87 for jets https://www.vepetersen.com/images/holleycatalog.pdf

I'm thinking I will try a 64 jet, and if it runs rich then I can back down to a 63.

I called Holley this morning, and they agreed a bigger jet could help, but referred me to the Daytona Parts Company for tech support on classic carburetors. Daytona's line was busy so I called Mike's Carburetor Parts. They're not taking tech calls right now due to the pandemic, so I emailed my question along with the pictures I've posted in this thread. Then I called Daytona back. The rep was very helpful, told me how to check the power valve circuit (carb cleaner sprayed into it should appear in the main well and at the main jet), and told me the original jet size is 62, which agrees with matv91's info a few posts back. The power valve and circuit seem to be fine. He recommended a 64 jet with my higher compression and slightly hot cam.

Within a half hour of emailing Mike's I got this reply:

You have way more patience than I do. I fixed all the issues with my Holley 1945 by tossing it into the trash and rebuilding a Holley 1920. I did a ton of work trying to get mine running right, even having the throttle bores rebushed. It never ran right.

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If it was easy, everybody would be doing it.

Generally I really enjoy fixing things that can be fixed, and making things work they way they were designed to, within reason. Plus I enjoy learning about how things work. When I'm on my 10th classic car and have seen it all, maybe I'll have less patience.

While awaiting my larger jets, I pulled the distributor to look at the springs. I haven't taken it apart, but there's a yellow (green?) spring on one side and a larger red one with a loop end on the other side. Reading some other threads here, I take it the yellow one is always engaged and the red one engages only at higher RPM.

Inside the governor housing, under the phenolic washer, I found a bunch of crumbly dirt that might be old foam (red arrow in the first picture). I'm not sure what purpose that might have served, but I cleaned it out. Also, are the dot markings (blue arrow) some kind of month code?

The other two pictures show the springs. I note that the slot in the governor base collar was toward the weight with the lighter spring on it. The spring colors are yellow/green and reddish brown if that means anything.

I rebuilt the carburetor with a larger jet (now 64, was 61) and a higher float setting (I noticed the note that the float is measured with the gasket in place, which I don't think I noticed before).

I also rebuilt the distributor, replacing my yellow-green spring with a heavier green one from the kit sold by Charles Brooks (bigslant6fan@yahoo.com). For the other spring I kept the original heavy brown one with the long loop end. I did not shorten the slots yet.

I went for a test drive with initial timing at 0 and noticed much less detonation. Now it only happens when I floor it on the highway. I think the next step is to finish burning through this 6-month-old tank of gas and try higher octane. If it's still doing it on fresh higher-octane gas, I'll try an even heavier spring in the distributor, and if that doesn't work then shorten the slots.

What do your spark plugs look like now?

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

Less antiseize on the threads, for one thing. Here's #2.

Still too hot. Back off to № 6 plugs linked previously before you take out too much spark advance and start hurting your mileage that way.

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

There may be a hidden vacuum leak in the egr vacuum amplifier. Is that still hooked up? Wonder if that might help light throttle ping if working?

Posted April 14 -2018

Down loaded your recent plug picture. If look real close at tip of plugs, no 6 is little different color. Just a guess based on picture,s. Too hot of plug can cause ping in even a stock slant six. Much cooler plugs is the next step.

I installed the cooler plugs (NGK ZFR6F-GP) gapped to 0.035". I've only driven 10 miles with them, but the detonation is about the same as with the hotter plugs. That is, it's much better than it was before I installed the bigger jet, but still occurs at WOT above about 2600 RPM. Here are pics of the #2 and #6 plugs after the drive.