I just got done changing my modified '83 from a dual carb side draft to a brand new single Weber 36 syncro downdraft and stock manifold. I have no emissions. The stock manifold was bead blasted, all ports were chase tapped and plugged (with locktite sealer). The water plate was removed and plugs were fabbed and tig welded in place. The only manifold vacuum ports used are for the brake booster and PCV (new). I have a mystery whistle only under fairly heavy load conditions. I have an Innovate wide band air/fuel ratio meter in use and while the whistle occurs the A/F does lean. I can not duplicate this in the garage. Any ideas? I did remove the carb gasket and riser gasket and sealed both with locktite orange gasket sealer.

 

is the vacuum advance port on the carb plugged? Since you said the only vacs you have in use is the PCV and BB. any VCV's still on there and not plugged up?

 

Yes, the advance port on the carb is hooked to the dist. Forgot that one.

 

is it hooked via a full hose or is it hooked into the steel vacuum rail first? What about the VSV's?

 

All three vacuum connections are direct with new hose. All the factory lines, switches, EGR parts and connections are gone and/or plugged correctly. All of this was done prior to the carb swap and did not leak before. The only parts actually changed are the carb and intake. The leak is very difficult to find due to the fact that it only occurs under driving load conditions. I'm guessing a very small gasket leak somewhere?

 

two piece carb adapter? Was the carb new? What about the crank case vent hole on the bottom of the air filter if there is one, you have that blocked off if not in use? That wouldn't cause you to be lean, but it might cause that whistle.