Hi Miker, thanks for the reply. I am looking at the chart now for a 1403 and the #24 location I believe is asking for only a rod change. Am I reading this wrong? here is the link to my chart. http://www.edelbrock.com/automotive/misc/tech-center/install/1000/1404_manual.pdf

From the manual that should have come with the carb. It's available online if you need to print one.


"High Altitude
Altitude has a direct effect on the operation of most carburetors. As the altitude increases, the air becomes less dense so a carburetor, originally calibrated at low altitude, delivers too much fuel and the engine runs richer. If the preceding tuning procedure is performed on an Edelbrock Performer Series carburetor, a proper high altitude calibration will result. If the vehicle was calibrated at lower altitude, however, and is to be driven at high altitude temporarily, it is not necessary to repeat the complete calibration procedure. Instead, use the rule of: “2% leaner per 1500 feet” and the Calibration Reference Chart for your model carburetor. For example, with a #1405 at baseline calibration (location #1 on the chart) and intended operation
at 6000 ft. altitude, you would want 6000 divided by 1500 x 2% = 8% leaner calibration. That would be location #24 on the chart which would require only a rod and jet change."

The manual is pretty dry reading and at first seems confusing, but if you stay after it it makes sense. They show a little larger jets in the chart, so maybe you've already made the altitude adjustment. You might also search spacers here. I think an open spacer might not be optimum for your motor, but someone who really knows will chime in.


miker
55 bird, 32 cabrio F code
Kent, WA
Tucson, AZ

Howdy folks,

Well I finally have my truck running after a full engine rebuild. Its a 59 292 bored.060 with a mummert aluminum intake and headers. It has a mild cam. 
My question is I had it over carbed I think with a 625 street demon carb. So the engine builder recommended a edelbrock 1403 500cfm carb with a 1" open plenum spacer. I live in Longmont CO and we are 4,984 feet above sea level. Anyone out there live in co and tune this carb for a y-block. I have tried every different spring and the strongest ones ( silver ) seem to work best. For the jets Edelbrock recommended 83 jet for primary and 92 for secondary. I tried several different metering rods and the stocks 6552 seem to be ok. The truck seems to have a small bit of lag when you really get into it. Its not a stumble but the pick up i not instantaneous. Any other tuning hits would help tons. Thanks folks.