While rebuilding my carb I noticed that one of the main jets had cracked slightly where the slot is for the screwdriver. I went ahead and used it but this got me thinking....there are different sized jets....which one is correct for 6000' + for us here in CO?

http://www.carburetor-parts.com/Autolit ... /120-4.htm

Thanks.

I'm also wondering what guys are using. I have a Holley truck avenger 470 out of the box with stock jets. I have heard that most guys change them for altitude. Mine seems to run fine but I'm still curious. Hope there is a carb guru that can shed some light on this topic.

Do a search. Zilla posted up the suggested part numbers for the 600cfm Edelbrock performer.

I have a BG 750 and a Holley 600. Two different motors and they both are very happy with 65. I have gone as low as 58 above 11,000 ft. The big thing is the power valve. I use a single stage 2.5in HG. If the power valve is too big it will mess with what you think is your jetting. I have also used the power valve block off and just trusted the jets but it falls on it face when you need the extra burst of fuel. Don't over CFM. I have a 500in motor that actaully runs better around town on a 600cfm carb. If you over carb it doesn't have velocity and won't mix. I have a friend that runs a G.A.M. at Erie. The rules used to limit them at 490cfm. He still made 500+HP and instant throttle reponse.