Most likely just intake manifold gasket failing.
It happens with 4 and 8.
I wouldn’t get too excited until you can dig in more.

Thanks for posting this i have a few 3 barrels i always wanted to try out. I remember Barry R doing some dyno work years ago and the 3 barrel beat them all except a dominator. So just drilling the hole from .040 to .070 is the first step?

Is standard procedure for most any builder. .063-.076 depending on engine characteristics.
I like to make the pvcr removable so that end is tunable. Makes it nice to find a happy cruise jetting and adjust your wot fuel.

A nice touch is to add a restriction on the face of the VS housing where it attaches to the main body as well.
Allows you to tailor the restriction without taking apart the housing and potentially ripping the Vs diaphragm. Metering plate main feed can be done the same way.

Would be very enjoyable to dial one of these in on a dyno with these three adjustments.

But, Drew since your so experienced and know it all, I've got nothing more to say.

Scott, I agree with you 100% on post 1967 carbs.
Post 67, quality control and outside vendor usage fluctuated a lot more.
I kinda went down this rabbit hole some time ago lol.

I have studied the original earlier carbs extensively and find my chromate matches what is seen in the originals (once it calms down after a year or two).
The pictures I post are typically right after the coating is applied. I save some restored parts for years to see how it ages. Once it mellows down my stuff gets darker and less blingy.
I’ve shown nos stuff vs some of mine a few years later and it isn’t that far off.

That said, my personal view is any coating is original once…..  after that it is just going to be different. I wasn’t at the Holley factory in 1964, nor was anyone else I know, so we are just throwing darts blindfolded anyhow.

Only a few people do partial jobs.
I’m not one of them at this time.

My point was, the wet blasting didn’t cause the issue.


And yes, that is why I told the customer I would not use a metering block.

There is a whole 300 page book that I could write about this.


Why are you certain that variable was the issue?

Small vac leak?
Timing dropping out at that rpm?
At that rpm you probably aren’t fully on the mains so some idle fuel is in play.

Rule out stuff and narrow it down