Hi all,
Is the hot air tube regularly in 3 pieces?
Mine is.
If so, do you seal the connections at the
manifold exits, or is just sticking the two ends in
enough pressure for the choke to work?
Thanks, André
PS: 1966 425 w. 2bbl

 

Most are three pieces. No need to seal the joints. Slip fit is fine.

The way this works is a small vacuum port in the carb choke housing pulls outside air in thru the choke tubes. There's the outside air intake tube, the choke stove tube (in the intake exhaust crossover passage under the carb) and the tube from manifold to choke housing.

Unless you have a burned out choke stove tube, no need to seal the joints. A burned out tube will show itself first as a pfft-pfft exhaust leak at the intake end of the tubes and later as a burned out choke thermostat.

 

Thanks for the detailed answer. So that's not the problem :-D

 

On my 1966 Cadillac 429 it was one crossover piece in the intake manifold. There was a spiral inside the tube. As I remember all big block GMs from late 50s through 60s used the same piece I got one for a 1960 Olds and it worked in my 1966.

So one piece was buried in the intake on mine the second piece was the spiral the third is the chimney that comes out of the intake into the carb. This may be similar on the Olds 425. This was the Cadillac 429 setup. The pieces were not attached other than pressed into each other since they had flares on the ends. The only screw in piece was the external chimney part into the carb, the intake end just pressed into the crossover piece.

The burnt choke thermostat is correct, also the carb itself will be fouled with exhaust fumes too.