A12 carb help needed

[Joe Latessa]

Putting together a 70 Charger RT with original A12 carbs and manifold.
Secondary metering plates were already opened up to over .090
What were original plate openings?
I'm an original RR A12 owner, totalled it in 1971 ouch!!!

I think I remember .079 main and .029 idle as stock.
The trick then was either front or back (can't remember) was opened larger than the other and staggered sizes in one plate.

Our 440 has the 286/286 .484 lift purple cam, hooker super comp 1-7/8 headers, enlarged intakes and exhaust with bowl contouring and a multi angle valve job, this in front of a 727.

Thanks in advance....Joe

 

[moparstuart]

welcome

 

[Joe Latessa]

Thanks, Moparstuart

I'm an old piston head from way back. first fast car was a 66 new Yorker with the 440 TNT package i.e. 3.23 gears dual exhaust and a dual snorkle air cleaner, it went 15.60s at 93 mph with little Polyglas tires.

Hope to learn something here and maybe I can contribute from my memory bank

Joe

 

[69 Runner]

Your best bet is to buy some new metering plates and either shelve those, or modify them to accept "regular" Holley jets

 

[dantrap]

Joe, this is from the old DC blue book, Chrysler engineering 1976.
This is for a cast iron intake mani.

With mani. heat Throttle side Diaphragm side

Front Carb- MMO .093 drill .089 drill
Center carb Jets #64 #64
Center carb-PVCR .052 drill .052 drill
Rear carb-MMO .093 drill .089 drill

Mani heat blocked Throttle side Diaphragm side

Front Carb- MMO .089 drill .086 drill
Center carb Jets #63 #63
Center carb-PVCR .043 drill .052 drill
Rear carb-MMO .093 drill .083 drill

MMO is main metering orifice
PVCR is Power valve Channel Restriction

In all cases the proper size drill is used to open up the PVCR, which is located behind the power valve.

These mods are for maximum off road power with a most stock or mild combo.

 

[Joe Latessa]

Thanks Dan, that's a start, I wonder how these numbers translate to an Aluminum manifold, any ideas?

I would imagine runners are the same, would Al. run hotter or colder as it transfers temperature much more quickly than Iron??

I have heat crossover blocked and plan on using some sort of cold air set-up.

Thanks,
Joe

 

[dantrap]

Hi Joe,

Aluminum Mani heat blocked Throttle side Diaphragm side:

Front Carb- MMO .089 drill .089 drill
Center carb Jets #63 #63
Center carb-PVCR .041 drill .049 drill
Rear carb-MMO .093 drill .093 drill

 

[Joe Latessa]

Thanks, Dan, that'll get me close.

Joe