Stromberg gas leak repair-fail; seeking advise

[Q]

After updating fluids, hoses, fuel filter, timing chain cover and tensioner on "Q", sV mostly stock alpine which was running well, we noticed the Stromberg carbs leaking at the bottom. After searching the forum and consulting the WSM, we unscrewed the bushing and replaced the o-rings with plumbing (nitrile I hope) rings from Ace. Upon replacement, the leaks stopped, but it also appears 2 of the 4 cylinders are not firing now. We do have good condensor spark. My buddy thinks the plugs are fouled (they were clean when we checked compression-~140 at each cylinder) after cranking the engine to get the new fuel lines re-filled, but I think we missed something regarding the carburator. I did catch the carb bushing parts in a bowl when unscrewing it-so I don't think anything is missing.

To complicate matters, I entered my first car show October 13 but am away on business. I'll have one day to fix the engine problem and groom the car for the show on my return. Has anyone on the fourm experienced this problem, and can you share the solution?

Appreciate all the collected knowledge on this site-thanks in advance!

 

[RootesRich]

Which two cylinders do you believe are not firing?

 

[RootesRooter]

Yes, by all means check the plugs first.

Couple of basic questions first that might help others to solve your problem: Have you worked on Strombergs before? Did you have the carbs & manifold assembly off the car when you changed the o-ring? Any other parts disassembled during the o-ring fix?

With the air cleaners off, are the air pistons moving freely up and down in both carbs? (you may replaced the parts out of alignment, binding the needle on the air piston) If they move, do they move exactly in sync? With the engine running, can you see fuel spraying when you open up the throttle? Could you have accidentally tightened the mixture adjustment screw when you refit the parts? Could you have bumped the float in the bowl out of adjustment?

Does the engine run OK while stopped but seem to be missing two cylinders when you put it in gear and drive it? That could indicate a leaking diaphram.

 

[RootesRooter]

One more question for clarity: had the car been running well AFTER you replaced all those parts and fluids, or did you notice the leak and work on the carb before you re-fired it?

 

[Q]

Hi Folks-thanks for your attention to this query!

Unfortunately I don't have the manual to address the parts by name, but do recall the "bushing" (seen external to bottom of the carb bowl appears to be the "lock-nut" to this brass bushing) and the o-ring was #18 on the exploded diagram. The bushing contains the fuel mixture adjustment valve/screw (turn with a coin) at the lowest part of the bushing assembly.

Specific answers to your questions are as follows:
What 2cylinders appear not to fire-my buddy reassembled the bushing/o-rings after I left. He thought it was the front two (#1 & 2 but how could you tell....?). No objective measurements were performed.

We have zero Stromberg experience, though my buddy is the car guy and I am the "read the manual" guy. Significant review of the WSM and parts book before unscrewing the bushing and replacing the o-ring seemed to indicate it wouldn't go fubar (but it did!). Some on-line diagrams seem to imply this bushing participates in "centralizing the needle." (Uh oh).

The carbs were left on the car, filters in place. I believe only the front carb was "repaired" with the o-ring, and that appears to be the non-functional carb. Only the bushing was unscrewed from the bottom of the float bowl.

The mixture screw may indeed be overtightened. My buddy noted he could adjust the screw in the bushing with no change in the engine however. I am doubtful that we bumped the float (but never say never).

The car has not been on the road since the o-ring replacement. Everybody had to leave, so we'll be at it again Oct 12. Thinking back, we did run the engine with no recognized idle or rough running after the self-service, prior to observing the carburetor leaks. I recall listening for the "sweing machine" sound that should have gone away after fixing the tensioner rubber.