I had a Holley 390, it was an older model and it would never mix right. I am not a mechanic by any stretch but usually I can tinker things but no luck with the holley. I sold it, bought an Eldebrock 500 and never have had any trouble. I Know Woody is sold on Holleys and tried to talk me thru mine but it was not worth it. I sold it on Ebay for 150 more than I paid for the new eldebrock.