This is another one of those "i purchased "rebuilt" carbs, instead of rebuilding them myself" threads.   I've been sitting on some rebuilt carbs (purchased online), MSA 6-1 Header, and MSA exhaust for almost a year now... Finally had the opportunity to install them this past weekend.  I ended up pulling the ARA AC unit out as well. 

Before I end up pulling the front carb completely, just wanted to hear more opinions. 

Installed all the parts mentioned above and cleaned up anything I could as I went.  Also threw in some BSPT 1/2" and 1/4" plugs in the balance tube.  New blocks/gaskets for the carbs as well. 

Car fires  up cold with the choke.  Then after its @ operating temp, it'll start right up each time.  Idle is about 1500ish.  I started out originally with the jets turned all the way up and then down 2 full turns and the throttle adjustment nuts all the way in and then back out 2 turns. No matter what i did with the front carb, i could only get it to increase air flow, never reduce.  The synchrometer i'm using shows 7 kg/h on the rear carb and 20-30 kg/h on the front carb. 

Fast idle screw is all the way back out, and I pulled the throttle adjustment screw out of the front carb completely just for the hell of it (thinking that maybe the butterfly wasnt closing completely).  I took some time last night to search on the forums and google for anything.  Everything pointed to maybe a vacuum leak somewhere.  So today, i went and checked all the vacuum lines and plugs.  I sprayed a little carb cleaner in various areas (balance tube gaskets and blocks, intake manifold where it meets the head, line that goes to the brake booster, carb blocks/gasket area etc) and never got the rpms to increase. 

Also pulled the dashpots and cylinders and made sure they were clean on the inside.  I used 3 in 1 oil for the dampers.  Return springs on the throttles look good and i believe attached correctly.  Vacuum advance is plugged into the front carb. 

I have new plugs, points, rotor, cap, plug wires, coil etc. and they are ready to go in but I wanted to make sure I could get the car to idle under 1000 before i started messing with any of that.  The car ran fine on the old SU carbs, compression was good, i believe the timing was at 10 degrees @ idle 700 rpms 

 

 

Shouldn't the choke cable be all the way down? Looks like yours is up.

Here's mine with the choke off.

47 minutes ago, siteunseen said:

Here's mine with the choke off.

Thanks, it did seem a little stuck on the return.  I unhooked the choke cables and the air flow dropped down to between 15-20.  The throttle adjust is still basically all the way out though so still trying to mess with it. 

Going to swap the front carb with my other one at this point to see if the issue continues. 

Welp, without even an adjustment a simple swap over to the old carb and voila... issue gone.  So now I guess I need to breakdown this carb and see where it went wrong with the previous owners rebuild. 

I think I found the problem.  Butterfly had ZERO play and the shaft holding it looks bent... 

This may be of some help. I've never seen that before myself.

Here's a bunch of threads on those shafts...

https://www.google.com/search?client=ms-android-americamovil-us-revc&ei=S44PX-W8LsuOggebw6ngCA&q=bent+su+butterfly+shaft+classiczcars.com&oq=bent+su+butterfly+shaft+classiczcars.com&gs_lcp=ChNtb2JpbGUtZ3dzLXdpei1zZXJwEANQAFgAYJ41aABwAHgAgAHdAYgB3QGSAQMyLTGYAQA&sclient=mobile-gws-wiz-serp

 Sell it to ZTherapy.

1 minute ago, Mark Maras said:

 Sell it to ZTherapy.

They buy carbs? 

I think i'll purchase the parts I need for the "rebuilt" carb and put it back together.  Then throw it back in the car.  Then maybe I'll rebuild and clean up the old pair that I have. 

One of the problems with old SUs is the butterfly shaft bushings get worn and leak. Z therapy replaces them with roller bearings instead of brass bushings. Good luck though and post up your journey. 

2 hours ago, research monkey said:

I think I found the problem.  Butterfly had ZERO play and the shaft holding it looks bent... 

The shaft screws are normally staked. It looks like someone got a little carried away staking that one. the shafts bend easily...

Anyone have recommended vendors in the US for specific parts on an SU carb?