Good to know! Thanks for posting your results.

It has been a while and I re-built the SU's and made sure the damper drops freely while I was rebuilding the carbs. Now the car starts, idles and runs fine...everytime

Float needles sticking.
Tap the float lids with a screwdriver handle they usually release, they may be gummed up and need cleaning.
The white plastic ones seem more prone to this issue the better ones are the viton ones brass with black rubber tips.
Also the jets get gummed up especially if the car has sat a while with ethanol fuel in it.

interesting thread.... i’ve the same issues with my 1.5” dual setup. 

It has been a while, here now is the new situation. I check the fuel pump and it works, I checked for spark at the plugs and it does have spark. It will not start? I spray starting fluid on the carbs, it will start briefly and then die. I did this a couple of times. but it would not start on its own so I have concluded it is a fuel issue at the carbs. Any ideas?

Thanks

It's been awhile now but I'm reasonably sure it's an early MSC 30 degree manifold. No disrespect to anyone but way back I bought all the books I could find on theroy and SU/weber carbs and read them like novels and reread till I almost had a clue. After awhile the black magic, smoke and mirrors started to clear. I still get stumped now and then. I'll look for a good set of carbs and see what I can do to help. I have no expectation of reading this whole mess.  

CTR

I bought a mini manifold (20) from Coopertune. The carb farther from the radiator needs to be richer if not the car would not rev up and if I make it richer it works better and when they are warmed up making it richer would not change the idle when you push on the pin to raise the dashpot. I was thinking of buying a good used twin carb or just save up for a brand new one or even just have this set rebuilt which ever way would be more economical.

They look level to me but maybe it has a 20 degree Spridget manifold, any of this should not cause it to backfire though.

Did I miss something?

Do these carbs have the 30 degree float bowls for a Mini?

Yes. If it is still on choke it will not be lean, if it is off choke try pulling the choke out a little to see if it helps but it could also be timing.

Could a lean mixture cause backfiring when the car has not reached normal operating temperature?

OK a cheap way to balance the carbs without a sychronizer is to use a length of 1/4 inch or 5/16 fuel hose or any small hose for that matter. After the engine is warmed up loosen up the carb linkage that connects the two carbs then place the hose near one carb throat opening and listen to the hiss sound then go to the other carb and adjust the throttle stop so the hiss is the same, at that point they are synched. You then turn the throttle stop screws up or down equally until you find the right idle speed and then reclamp the linkage so both carb open at the same time.

All this should be done when the mixture, timing, points, plugs are all in spec and you will need to re check your mixture afterwards, when you lift the pistons the rev's should rise slightly then drop off.

Have a look at this //www.sonic.net/~kyle/su.html and this //store.edelbrock.com/4025uni-synafor1and2barrelcarbs.aspx

What do you mean? balancing by the throttle stop screws? Could it be that the hose from the float bowls to the jet is clogged?

Did you balance them when you installed them ? It sounds like they may not be synchronized.

What could be wrong on the 1 carb (closer to the radiator) when I press on the lift pin the idle does not change. On the other carb the mixture is just right when I press on the lift pin the idle rises a little bit and then goes down to almost dead. Any suggestions?

 

 

Okay Thanks

The Jet (needle hole) needs to be turned up to the bridge so that it is level and then turned down twelve flats or two full turns on the adjustment nut underneath, that should give you a decent starting point.

Does the needle hole need to be close to flush with the bridge as a starting point?