Vacuum in Float Bowl

[Rhett]

I rebuilt a 76 Buick 17056240 for my 73 Stage 1, and now have an odd problem. I used all parts from Cliff, and seemingly put it together correctly cause it runs fairly well. I knocked the APT plug out and threaded in the plug.

But while the car is running and take the APT plug out, the car has vacuum in the float bowl and the idle takes a dive....

I used the airhorn gasket that came with the kit, and I dont remember if there was multiple gaskets to choose from....

What did I do wrong?

[Rhett]

or now that I think of it, is that normal because of the vacuum on the primary rod hanger piston? I wouldnt thnk it would leak around it.....?

[Cliff Ruggles]

There shouldn't be any vacuum on the float bowl, and leakage around the power piston would be minimal.  Did you install a new plastic split collar PP retainer from our kit?.....Cliff

[Rhett]

Ha! I didnt, probably because I had no idea what it was...although I dont recall the existing one to have been particularly loose or mangled, it did retain the PP without an issue with minor staking.

In an unrelated question - do you sell repacement ICRs? I overdrilled mine in an attempt to fix an off idle stumble that turned out to be electrical, and as you said "that things now got enough idle for a top fueler".....if you have them, how do you get the old ones out? Drill them?

[Cliff Ruggles]

Yes, we sell them, drive in type, .046".

I'd install the new retainer for the PP while you are in there....Cliff

[Rhett]

I'll call today and order the stuff - do you drill the old ICRs out or drive them in over the old ones?

Thanks - RT

[Cliff Ruggles]

They spin right out with a .113" drill bit.  If not, they can be pulled out carefully with a drywall screw.....Cliff

[Rhett]

Took this carb apart today and found the issue the APT screw had wound all the way out of the threads and vacuum was coming through from the baseplate. Must somehow be tied into the same vacuum circuit as the power piston.