1956 Buick super idle issues

[Guest Grandpacharli]

Hi, All I’m new to the Buick scene and from the UK. The car is completely standard and ran perfectly when I imported the car from Canada apart from the know hesitation when pulling of on a Rochester 4gc carburettor, so I purchased a rebuild kit and rebuilt the carburettor and refitted and it started right up and idled just as it did but maybe a little lower revs. After that I replaced all the vac lines for the wipers as they where deteriorated. The following day I took the car for it’s first drive but I found it hard to settle once the choke was off and it kept stalling and I also found it backfired slightly but hasn’t done that since . Once warm I took it round the block and it stalled so I adjusted the two idle screws on the front and it ran fine around the block. I got back home and noticed the car shaking and the idle was running rough. Now I can’t seem to get rid of the issue. What puzzles me is that it ran completely fine when I rebuild the carb and put it back together but the next day it’s not so! The idle screws are wound right out so it’s as if there limited fuel or a vac leak but I’ve tested everwhere. 

 

Could it be the ignition system or plugs baring in mind it runs perfectly once the primary jets are open? When the throttle is slightly engaged it runs better as it does when I go up the Rev range but the idle is just rubbish. 

 

Ive worked on American cars previously and rebuilt a 65 c10 from the ground up so my knowledge okay but not great. 

 

Pulling my my hair out!

 

thanks in advance!

 

matt

 

 

 

 

 

[Bhigdog]

Sounds like a vacuum leak. Likely caused by something gone awry with the rebuild/vacuum line replacement. Put a vacuum gauge on it right off.....................Bob

[Beemon]

What's your idle speed? 

[old-tank]

Always be sure ignition is not the issue.

Components:  plugs, wires, cap, rotor, points, condenser, coil, vacuum advance

Settings: timing, dwell, compression check, vacuum gauge

Here in the USA the winter blend gasoline is highly volatile due to added ethanol and butane...none of my carbureted cars run well and the gas mileage is horrible.

[Guest Grandpacharli]

6 minutes ago, old-tank said:

Always be sure ignition is not the issue.

Components:  plugs, wires, cap, rotor, points, condenser, coil, vacuum advance

Settings: timing, dwell, compression check, vacuum gauge

Here in the USA the winter blend gasoline is highly volatile due to added ethanol and butane...none of my carbureted cars run well and the gas mileage is horrible.

Thanks for the fast response guys,

 

 

I’m going to test the ignition components  tomorrow, I just feel if it was running okay before and if it’s running fine at high revs it shouldn’t be that. Worth a shot though . 

 

Ive searched everywhere for vacuum leaks with carb cleaner. There’s  only one vac port on the carb which leads to the advance and there’s no leaks there. None at the carb base. The vac line that leads from the manifold to the fuel pump I noticed that at the fuel pump end where the metal vacuum line connects to a rubber line and then back into a steel line it doesn’t have a very tight connection but it was like that before so why would it be different now. It’s strange . I might try the cigar smoke truck to see if it’s leaking. 

 

Many Thanks

 

 

[Bhigdog]

5 hours ago, Grandpacharli said:

I purchased a rebuild kit and rebuilt the carburettor

 

5 hours ago, Grandpacharli said:

After that I replaced all the vac lines for the wipers

 

If there  is a new problem after you do something always suspect what you did. A vacuum gauge will often give clues to many problems. ..................Bob

[JohnD1956]

Have you checked to make sure the automatic choke is opening all the way?