holley 4160 secondary metering plate

Is there a number stamped in the middle of the plates like in the picture below.?

The one in the picture is stamped with an upside down 59

That'll tell you the equivalent jet sizing of the idle and main orifices by referencing a chart .

If you have the numbers but can't find them on a chart, post them here and maybe you'll get it figured out. Lots of charts out there but they don't all list the same numbers.

Or............... post the list numbers on both and that may help.

Here's a chart or 2.

Not necessarily complete though. You won't find a 59 on it

i was messing with the 1983 carburetor that i rebuilt a few years ago and think i found the vacuum leak. Turns out the secondary is not closing all the way due to the vacuum diaphragm spring. Dont get new spring in the kit.    I bent the linkage a little to put some closing pressure on the secondaries.   I also stretched the spring a little

no issue with primary. fact is the idle screw backed out all the way.   
Unit is not installed, I sat and messed with it and found secondary was not closing all the way. After manipulating the spring it did close all the way consistently.   

Primary is a metering block not a plate.

Guess i need to be more descriptive

Holding the unit upside down with main throttle open all the way, i can manually open the secondary and watch it slowly close but it stops short allowing air gap in the secondary butterfly.    I can however manually close the secondary, I did this operation multi times with same result. I wd 440 all joints with same result and ruled out slop in the bearing surface.   I then opened the vacuum pot and pulled the spring which is original 35 years old. I pulled it just a little without deforming it and re installed. I then Operated the secondary valve as before and noted that it consistently closed.   I also did bend the linkage with the primary idle screw backed out all the way and now there is a small negative load on the secondary to keep it closed at idle.   

as soon as i get a new rebuild kit since i need some of the gaskets and cross over tube o rings i will reinstall it and see if it works,   I have a second unit that is new but for some reason the engine gets less top end with the new one.   

I also compared apples to apples with the old and new one on the bench together to compare operation.      

I will likely get a spring kit and try a few since old one was compressed. By the way the secondaries did open kind of erratic.   not seamless transition. it kind of kicked on hard like a weaker spring was being used.   So i am pretty sure the spring is the main issue here, secondary issue being paint.   

Made a frankenstein. works perfect. took the spring from new unit and put in in the old one. it now works perfect at low and high end. actually turning 4700 wot.   couple of years ago i had original prop re pitched to 13-12 due to WOT issues.   Plan to have it put back 13 square.   

The spring in the secondary diaphragm pot is a return spring along with a gauging device.   It does control opening and closing etc.

Spring from new unit was completely different, its about 3 inches long when fully sprung and old one is about inch and a half.   

I did consider ;leaving it alone. Kind of a waste to spend money on the old one.