I would like to find out what jet size would be optimum for my carb. I am running at sea level (florida). I have a 383 and a 650 holley(old kind with no site glass in bowl)also a 1" spacer. New out of the box the low idle or front jets were 85's I think and I dropped them down 1 size which cured it from runnning rich at idle. Should the rear or high speed jets be dropped as well? Should all 4 be the same? I am thinking its running rich on top as well. Any advice would be appreciated. Thanks, Chris

On your holly you have 2 screws which basically control how rich your car runs at idle your jeting on the other hand is completley different rejet it for top end and then adjust your idle fuel mixture, I like to run a little bit bigger jet in the front than the rear due to laws of physics pulling the fuel back so it balances out. I set my car up this way and it has worked well for years I am not really good with carbs but I get buy just fine (? Maybe ?) I run 72's up front and 70's in back and my spark plugs stay really pretty I set the idle kind of lean and I use the sound of the motor and smell the exhaust to make sure its a little lean but top end I keep just a hair rich! hope this helps