Timing for 383 automatic trans - what jets on a holley 750 with vac secondaries

[wantone]

Howdy again -
So- I recently looked at the MPG and I'm somewhere around 10mpg (speedo has wrong gear so odometer is going to be wrong) and I think that is not great.   My garage smells of lethal amounts of fumes so I am trying to tune it up.   Just bought a good timing light with a tach so I can verify my gauge tach (which I believe to be wrong).

S0 - i'm going to replace all my spark plugs with the champion rj12yc's and gap them to .035 and use some DE Gel.   Then i'm going to take my holley and jet down from 74 (or maybe 76?).  WHAT JET WOULD YOU USE?
My cam specs are attached - 262int/270exh

Keep in mind I have a Holley 3310 750cfm with vacuum secondaries and around 12-14 pounds vacuum. My squirter is think is a 37.

What timing would you use?  I'm a about 20-22 BTDC initial and I don't know what total (don't remember).    Where should I be in total?  36?

[cudabob496]

do you run engine while car is inside garage?

initial timing seems too high.

Cut it back to 10 BTDC at idle, and see how engine runs

[rUNCHARGER]

If it takes all the initial without pinging I would run it. Total should be 36. If the car is reasonably driveable I move up and down jet sizes.002 at a time.

Sheldon

[wantone]

I don't run the engine while in the garage no.

[cudabob496]

correct jet size can be determined by studying plugs, if don't have AFR meter.

Make adjutment, then put in new plug in #1, and observe color after running engine.

Also, jet size that comes with carb is usually good.

[jhaag]

Timing should be 18 to 20 initial with 36 total (initial + mech) as long as no detonation,and starts ok. Jets I would think about 72 primary and 78 secondary. I think your problem is primary throttle blades open too far at idle exposing too much transfer slot causing a stinky smell. 12 to 14 inches  of vacuum does not seem like much for that cam. Also you should not need #37 squirter on your setup. 27 or 30 should get it done. If you put the bigger squirter on to cover up a flat spot on acceleration, this is another indication you are too far into the transfer slot at idle. Take the carb off, turn itover and look at the setting, if you see more vertical slot exposed than the width of the slot, this is a problem  Open the secondary throttle blades slightly and close the primary. Trial and error is needed but the results will be well worth it.                                                                             

[Chryco Psycho]

The cam is likely a bg part of the smell you can get a cam with similar duration & a 112 * CL shorter duration  .
Jets come down the Plug color or egt readings , plugs should be a light tan color , going lean will make it run hotter so be careful .
 if you have a strong coil & good wires the plug gap can be be .040 - .045