Heh heh, I don't know. I *think* it's more or less to hide it and keep you from tampering with it. It might also keep air and dust from being suck in past the threads. Before you tamper with it,---if you want the valve to open sooner, you can install a shim under the spring inside the PV piston, that way you can always return it back to factory setting if you don't like it.
Also be aware that those 1945 carbs have a "gradient" power vavle. Some carb kits come with a replacement valve and I have discovered that these are non-gradient, they are either on or off. I can explain this in better detail later if you need it.

1920 Power valve--- isn't that operated by that vacuum diaphragm on the top of the carburetor? No adjustment like you are looking for. The carb kit comes with a new diaphram and spring as an assembly. The spring is calibrated. Seems to me once upon a time I had one of those carbs that has some plastic washers (with a slot in them) slipped over the shaft at the top of the PV spring next to the diaphragm. This would make the PV open sooner. I wonder how many of those washers have been thrown away at the carburetors very first rebuild decades ago? There is NOTHING to change or adjust in the metering block of those 1920 so don't mess with it and spoil it.

actually I only want to clean it thoroughly during an overhaul. That's the only contention that I have with my 1920, that you can't ensure every bit of crud is out of the metering block and you can't therefore exclude the block as a root cause if you have problems with the carb after it's back in the car for runup.

_________________
I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Well I just ran my rebuilt 1945 and it worked great, except now I've found an intermittent gasket leak where the wafer mates to the intake manifold on the head side. The gasket is new, and I retorqued the bolts holding the carb down and it's still there, luckily this is on the beater car so either I may try replacing the bolts with studs and nuts, or I may try the permatex fix .... or I cleaned out my garage and the super six setup that was on the feather duster is screaming for installation.....

The tell tale signs came from a rough idle after warmup and the choke pulled off, the vacuum gauge said I was getting 25" Hg at 800 rpm idling, then the tach took a dip to 600-800 and the vacuum went from 25 to 22....using the usual 'spray' method, the idle and vacuum returned after hosing down that side of the gasket, the retorque tightened the carb down but the leak is still there.... I'm gonna get it 'fixed' the thing ran good around the block and I like the #60 jet instead of the #58 from 1974....(suddenly those 2.76's don't feel that 'sluggish')

-D.Idiot

So how does it start when cold? That was the only problem I had. I was running 19 or 20Hg vacuum when hot. I think I had a #62 or 63 in mine. No matter, I have my 1920 running good now, with an open element air cleaner on for the warm months and a #60 jet. My gas milage has increased as well, a definite Good Thing. So, I think I will wait alittle bit before I screw with the 1945. When I got the carb from Reed, he had just rebuilt it, but I think I'll throw another kit at it and see if that helps. I really like the extra power it seems to give me. Just wondering, do you still have the spring at the end of the throttle shaft hooked up? With my return spring, it was way to stiff and I disconnected the one on mine.

None of my Duster's ever came with a return spring, the carb should already have one built into the other end of the throttle shaft (the one with the wierd metal 'flap')...

more later, tomorrow I get to play some more with the dual weber madness


-D.Idiot

Thats the one I disabled, the spring at the end of the throttle shaft. It wouldn't close the throttle all the way, and it was to stiff with a conventional return spring installed.

Eric- let me scrounge around in my garage. I may have the hardware to set you up a factory return spring.

Reed

No worries Reed, I have a return spring that works well with it. Nice and light, with enough "spring" to close the throttle plate all the way to idle.

Well, I finally found out where all the black crud was coming from. Someone on a different thread suggested my fuel filter diaphram was ruptured causing gas and oil to intermix. Sure enough, that was the problem. I then replaced oil, filter, air filter, fuel filter and plugs. The 1945 however was major crudded. I made a mistake of getting a reman rather than rebuil kit again. It had no acceleration. I tore it apart and found the check ball was the wrong size as was the pump piece, there was a stripped screw holding the pump rod and they had the wrong linkage rods on the carb. Anyway, I found a place to order a brand new Holley 1945 and expect it any day. I think at some point remans and rebuilds can no longer be done on older carbs. I'll let you know how that works.

Mike