7045264

[mcx]

Looking for info regarding the original prim jet/rod and sec rods on this 1975 Pontiac..thanks.

[Kenth]

#7045264, Application PONTIAC, LEMANS, GRAND PRIX 400,
Pri jets #72, Pri rods 40K, Sec rods DB #7047806,
Airvalves preload 1/2, Power piston spring 7029529.

[mcx]

Thank you....picked it up for ten bucks on EBay, I haven't had one of these before.

[mcx]

...I disassembled her today and recorded the following:
Prim jet 62
Prim rod 39
Sec rod  DB
Hanger O
Main bleed .067"
Lower Main bleed .0410"
Idle tubes ?
IDCR .0465"
Upper idle bleed .0595"
Lower idle bleed .0635"
Idle air bypass .1100" (base plate)
P.O.E. .0595"
Idle mixture holes .093"
...this is a real undesirable LOL android type core and the first I have gotten my hands on..interesting to pull out the android and see it's single rod and jet in the bottom of that void...It is a  Pontiac 800cfm casting with that mesh screen over the center/fuel bowl...this core also has the  upper idle bleeds drilled in the airhorn...it also has those very small bleed holes next to the center airhorn tubes(never seen those either in person).

[mcx]

I'm looking for suggestions on what to use to make the cast plug mounted over the aneroid jet/screw removable.
Also, what is a good starting point for setting this screw?

[Kenth]

Unless someone changed to a 1976 or later air horn it should have a brass plug above the APT adjustment.
I have seen it 1.5 - 2.0 turns up from lightly seated.
The idle tubes are .038" in these units.
#62 jets are way too small, i would use at least #70 if not #72 jets with the APT seated and tune from there. The primary rods should have a J or K suffix in 1975  units. Also, the secondary rods are too lean for any kind of performance usage.
And, all Pontiac V8 Quadrajets uses .070" +- .001" lower idle air bleeds.

[mcx]

 Kenth...thanks for the info
....it has a brass plug, I was looking for ideas as to what I could use to replace it with something that would be easier to take on and off.
This carb must have been modified as some point, as the APT  /aneroid (not sure the correct term on these one year casting) because that screw was 2 and 3/4  turns from bottom...maybe they were compensating for such a tiny primary jetting (62) ??
Anyhow, I'll change the jetting to your suggestion.

[4ever18]

In order to plug the hole and be able to get to the APT easily once the air horn is back on the carb, I tapped the the existing hole for a 3/8" x 24 thread brass allen head plug.   This will sit flush with the air horn and not interfere with the air cleaner.  Be sure to get a shallow (thin) plug, about 5/16, so that it doesn't bottom out on the APT screw.

Hope this helped.

Jay

[tayto]

dont tap the hole completely. I use a bottoming tap and leave it untapped @ the bottom so the plug won't screw all the way in

[Pav8427]

Hole in air horn is perfect tap size for 1/8 NPT allen plug. Also seals when using NPT.

[4ever18]

Be very careful using NPT plug.  The airhorn casting is fragile and an NPT plug is tapered so if you overtighten, it can crack the airhorn.

[Kenth]

For 1975 units you may drill a hole in the APT brass cup for a machine screw and lock the screw with a nut to pull the plug if needed.
Most times though i leave the brass plug out during testing and knock it back when finished.

[mcx]

Thanks to all who responded...I'll put your suggestions to work.