302 problems

Motor is in a 83 thunderbird. Added a cam 216 duration at 50 272 lift and heads off a 87 302 ho new intake and carb. I can not get it to run right at all. Had it timed to about 10 degrees advanced with the vacum disconnected at idle. Will idle ok but nail the throttle and it wants to fire back thru the carb. Tried moving the dist one tooth and now it wont start and makes a huge fireball out the carb instead of just backfiring. Any ideas on this I am at the end of my rope here. Its not even my car just trying to help a friend have a faster car. From looking at the pictures of the car before it was tore down it looks like the dist is in the right place now according to the position its in. But like I said it wont even start.
:mad: :CRY: :CRY: :(

Any help would be appreciated more then you would believe. I have built motors before and not had any problems but this I just can not figure out. Only things I know to do at this point is put the dist back to where it ran and back off the timing till it quits backfiring. We reused the stock pushrods to save a few bucks but they seemed to be the right length. I thought maybe they are a bit to long and the intake valves are not closing all the way causing it to backfire but I am so down I didnt feel like doing a compression test tonight to see if its got good compression or not.

I'd do a compression test. My friend had a 84 GT Mustang with a weird combination of 89 LTD 302 and some newer HO parts. I think he tried to run a carb on some of the new HO fuel injected heads and I think he had problems too. I think that those heads will work much better with fuel injection because of port angles, breathability, and the compression ratio you get from using them. But I could be wrong I know more about Chevy.

Are you using the right firing order for the cam? Some aftermarket cams use the 302 firing order, some the 351W. 15426378, or 13726548. The wrong one will fire on overlap, causing your backfiring.