I have a SMB 350 in my Jeep CJ7 which I rebuilt recently. The problem I am having is with vac advance disconncted the lowest I can set timing at with a light is about 30 degrees BTDC. Anything less and i backfire through the carb and cant get her to go over 40 MPH. Reset at 30 + and she runs great, with the acception of fuel mileage of about 10 MPG. THis does have a brand new Edlebrock 600 on it, originally thought I was having some problems with the old Carter that was on it before. I have restabbed the distributor several times and with the same outcome. My question is, Could i have gotten the timing chain off by a tooth or two to cause this problem. I would like a little advice before I go ripping this back apart. The jeep sits on 36's and does take some considerable work to get down into the engine compartment for this kind of work. Any help would be greatly appreciated. Thanks, Ryan