Random thoughts:
-Power valve is 1/2-28
Taps are available but they are expensive, and well, if the threads are rough, a tap might not make it better. You can block off the PV without installing a power valve ya know
Just block the signal hole.
-Stock Idle on that engine with that car was most likely 450-475rpm, these are not meant to idle at 800. I'll be home this weekend, I've got a Data sheet on that carb, also have a list 1619 on the shelf if you need me to measure anything.
I can also take a generic metering block and replicate the 1619 calibration on it, no biggie really, so could you, or anyone actually.
-You say smaller idle air bleeds in the 2v metering block, but metering blocks do not have idle air bleeds, those are in the main body. If you mean Idle feed restriction, that varies by calibration, but being 2v or 4v shouldn't matter. Emulsion setups for carbs prior to 1960 fluctuate wildly, really calibrations didn't get somewhat standardized until the early 60's.
-I like to pin gauge the hole for the idle mixture screws on older metering blocks. You'd be amazed at how off they can be.
-Older metering blocks I remove the emulsion tubes and replace them, same with the IFR if it is in the idle well. Trash there can make tuning impossible. Either snag the ifr with a drill bit and remove it, replace with a new brass restriction that is drilled to size, or relocate the ifr.
-I closely examined the photos from the one builder, I do not see High Speed air bleeds in the primary. Are they present? they should be there and around .028-.031 in size. In the picture I zoomed in on I only see the hole for the restriction but not the restriction itself..... if someone was blowing the carb out with high pressure air, they can easily blow out the old restriction, especially if it's clogged with trash.
