Upper Idle Air Bleeds

[jagness]

I'm working on a 17054907 for a 410 CID Olds with 10.3 : 1 compression, and this hydraulic flat tappet cam: 230/236 @ .050, 274/286 adv., .522/.522 lift, 112.0 LSA.

The owner rebuilt the carb sometime back and vacuum was very low at idle. When I took it apart, he had put way too much epoxy on the well plugs. The baseplate and main casting were glued together, but it also filled up the cavity in the baseplate so that the gasket couldn't seal. I've never seen one like that!

I have that problem fixed, but I just discovered that the upper idle air bleeds (in the airhorn) are .070". Way to big! How do I fix that?

Here's all of the idle circuit specs:
Idle tube, 0.038
Idle down channel, 0.059
Lower idle air bleed, 0.070
Upper Idle air bleed, 0.070
Idle bypass air, 0.110

[Cliff Ruggles]

Are there brass inserts in the upper idle airbleed locations or just drilled in the casting?...

[jagness]

No, it doesn't have brass inserts in the upper idle air bleeds.

[Kenth]

Are you sure you are measuring the idle bleeds in air horn?
There are two sets of air bleeds in the air horn, sizes from factory are .053" idle air bleeds and .070" main circuit air bleeds next to the idle air bleeds.

If the idle air bleeds are enlarged to .070 you may take them up to .120" for .046" brass inserts.

[jagness]

I tried to post a pic but it didn't work. I'm assuming that the bleeds closer to the front of the carb are the idle bleeds. The ones to the outside of the screw hole are the main bleeds. Those do have a brass insert and are .046".

[Frank400]

...or drill with a number 35 drill bit (.110") and install  a 6-32 setscrew which you can drill to the size you want.

[77cruiser]

That was my thoughts.

[Cliff Ruggles]

The MAB's are close to the two screws that attach the airhorn to the main casting.  The idle bleeds are closer to the front and much smaller often having brass inserts in them.

The MAB's should be around .070", the idle bleeds closer to .050" on that carb number....

[jagness]

Okay, I wasn't confused then about which bleeds were which. This carb is weird because the IABs (closer to the front) are .070 and have no inserts. The MABs (right next to the screw holes) have inserts and are .046.

Sounds like I'll have to install inserts in the IABs and enlarge the MABs quite a bit. Is it best to press in brass inserts or tap it for 6-32 set screws? I'm leaning toward brass inserts.

I wish I could post a pic. Maybe I'll email it to you.

Thanks everyones! Cliff's book, emails, and phone conversations, plus this message board, have helped me enormously on several Quadrajets now!

[jagness]

Installed brass inserts in the IABs, drilled to .048. Getting there!