Twisted Primary Throttle Plate?

[gzig5]

I'm trying not to bug you guys but this one has me stumped.  Tore the 4150 DP down for cleaning tonight.  It doesn't look too bad inside, but the accelerator pump diaphragms look very stiff and it was obviously leaking.  Also found a bad vacuum port plug.  These issues probably making it run super rich.  Now for the weird one.... the primary throttle plate looks like it could be twisted. In the pic you will see that the exposed transfer slots are different in the two bores.  I verified the plates were not bent with a ground straight edge.  I also measured from the throttle base plate to the round disc in the closed position and had a difference of ~0.030" between the two sides which is about how much more slot is exposed on the one side.  With the throttle wide open, you can visually see that they are not even.

1.   How could this happen? 
2.   will it affect idle significantly?
3.   If it will hurt, can I tweak the shaft a little without replacing it?

Never seen or heard of something like this.  Searches came up with zip.  This carburetor is starting to tick me off....

[Chryco Psycho]

Not good
Not sure how it would have been bent , if the shaft was stuck on one side & forced open it could twist the shaft
This will absolutely affect idle as 1/2 of the engine will run lean or rich , you may be able to twist it back or not 

[1 Wild R/T]

Backfire... Any signs of the throttle binding?  Have you actually pulled the throttle plates out to check them?  If you pull them I'd slide the shaft out & inspect it to...

If you haven't pulled the plates be aware there are tricks to do it without creating more problems than you fix.... The screws are staked, I've had good luck removing them by backing them out a little then going back in, back & forth repeatedly so the staked area straightens out & the screws come out without doing any damage.... 

Going back together there are also tricks.. Make sure the plates go back in the same bore, slip them in the shafts, get the screws started then with the idle speed screw backed out close the throttle fully, tap both ends of the throttle shaft with a plastic screwdriver handle, also tap the base plate, all the while keeping the throttle fully closed... Your centering the throttle plates...  Now while holding there snug he throttle plate screws.... And finally retake the screws, you need to support the back side of the screws while using a center punch to deform the end of the threaded portion..

[Bullitt-]

could worn shaft bushings be the culprit?

[gzig5]

Not good
Not sure how it would have been bent , if the shaft was stuck on one side & forced open it could twist the shaft
This will absolutely affect idle as 1/2 of the engine will run lean or rich , you may be able to twist it back or not

That's what I was afraid of.
There doesn't seem to be any radial play in the throttle shaft. The shaft rotates without binding but I haven't taken the spring off yet.  Will confirm.
I saw a couple procedures online for filing down the screws and the re-installation process. I'll try the back and forth thing, otherwise they'll get filed down and replaced later when I can get them in.
Unless someone has a better idea.....Before I pull it apart, I think I'm going to try tweaking it back by fitting a wood wedge in one bore with the plate fully open and then turn against it.  It will either move or it won't and that is probably the best way to do it without introducing radial runout.  If I fug it up I can tear it down and put it in the lathe to correct any runout.

[RUNCHARGER]

I agree with Randy that perhaps a backfire distorted a butterfly. The other possibility is that the shaft was drilled wrong to start with but I imagine they were all drilled in a fixture at the same time. The good thing is you are finding the problems.
If you have a caliper I would measure the backside of the two and see if they are twisted as well. At this point there isn't much to lose, I would remove the blade, adjust it and see if you can get it back together okay (I think you can no problem). Once it is back together I would use a lightsource to check to make sure it seals evenly around the bore.

[gzig5]

Oh, I have lots of calipers and mics and all manner of measuring equipment.  One of my other hobbies is machining and restoring/rebuilding old lathes and milling machines.  Not going to have room to do that anymore with the car here.  I should be able to make sure it is straight.  Funny thing, when you hold the base plate up to the light, the light rings in the bores are pretty much equal, so it isn't terribly off.   If it wasn't bent before I got it, the initial few startups had several backfires as the carb was dumping fuel, but they weren't as bad as some I've seen.

[1 Wild R/T]

I think you need to build a shop..... Trust me, I need to build a shop too....

[73440]

Oh, I have lots of calipers and mics and all manner of measuring equipment.  One of my other hobbies is machining and restoring/rebuilding old lathes and milling machines.

Love to see some pics of your old machinery.

[RUNCHARGER]

Ha, ha, I need a shop more than anyone. I'm looking for a deal on a 747 with engine problems.....

[Chryco Psycho]

Well the new member from Tennessee might be able to help with the Salvage airplane !!
I would try to tweak the plate in place rather then try to remove the screws

[gzig5]

I think you need to build a shop..... Trust me, I need to build a shop too....

Boy, I hear you.  Trying to get a quote on an 8' bump-out of the garage wall. That's all we have room for to stay within the setback specified by the subdivision.  I doubt it will be worth the cost if it's anything  like the bathroom remodel we did a few years back.  Need to figure out how to get my wife's car back in the garage before the winter comes again.  Might be time for a purge and shifted priorities.
I want to move to a place with room to grow but I have too much crap to move.  Six metal lathes, surface grinder, two milling machines, four welders, and on and on and on. My downstairs and garage shop are essentially a three foot aisle between the machines, tool boxes, and storage cabinets.

[Brads70]

I think you need to build a shop..... Trust me, I need to build a shop too....

Boy, I hear you.  Trying to get a quote on an 8' bump-out of the garage wall. That's all we have room for to stay within the setback specified by the subdivision.  I doubt it will be worth the cost if it's anything  like the bathroom remodel we did a few years back.  Need to figure out how to get my wife's car back in the garage before the winter comes again.  Might be time for a purge and shifted priorities.
I want to move to a place with room to grow but I have too much crap to move.  Six metal lathes, surface grinder, two milling machines, four welders, and on and on and on. My downstairs and garage shop are essentially a three foot aisle between the machines, tool boxes, and storage cabinets.

  I can relate!  Basement is getting pretty full too....

[gzig5]

The extra fender is laying on top of the South Bend 10L tool room lathe I picked up in December to rebuild.  The door blocks the entrance to the tiny path down the center of that stall.  All in all, its a good problem to have.  And I must admit, my cube and lab space at work look pretty much the same as that garage, so maybe it's just me.....

[73440]

Interesting machine , https://www.youtube.com/watch?v=PSRl0z1p0Lg


The tool room name, where does that come from , location or what it is used for ?
A motorcycle mechanic friend has a lathe or drill press that was used on an old Navy ship.
My Great Uncle was a machinist at DuffNorton making jacks, from about 1940-1970, I always felt like he could build or fix anything ! I would say it was him that got me interested in machines and such.