Whats the basic rule of thumb for jetting and altitude with a holley style carb? I have been told you decrease 1 jet size for every 2000 feet above sea level and I have been told you decrease 1 size for every 1000 feet above sea level.
I live 4000 feet above sea level and I run a quick fuel super street series 680cfm vaccum secondary carburetor on a 300 hp crate 360 magnum. The other day I noticed the engine was a little shakey and felt different so I decided to check my pugs, I had 3 fouled plugs. And I think this happened because I forgot to install the primary vent on thhe primary metering block and it flooded the crap out of my engine. This carburetor came with 68 main jets and 78 secondary jets and .070 idle air bleeds and .031 idle feed restrictors and .049 power valve channel restrictors and a 6.5hg power valve and .028 high speed bleeds.
Since getting this carburetor last summer I had to go down to .025 idle feed restrictors because the .031's were fouling plugs at idle and I am running .072 idle air bleeds and I went down to 64 main jets and 74 secondary jets and I went down to .045 power valve channel restrictors and I have left the high speed bleeds alone at .028 and I switched to a 9.5hg power valve.
I was wondering if it is possible that the 64 main jets are too big? Like I said I'm pretty sure the reason the plugs fouled was due to the vent that I didn't put back in on the primary metering block. I have my floats set to half way up the sight glass. And all 4 of my idle mixture screws are out about 1.25 turns on all 4 screws.
I have some holley .063 main jets I installed them and ran them for a couple of days and I didn't hear any pinging or feel anything significantly different then how it ran with the .064 main jets. So today I put the .064 main jets back in it and am going to see if I can tell a difference between them and the .063's.