302 rocker help

ok so i got a job and i built a mustang for a guy got the block bored .30 over and new performer intake spacer comp cams big mutha thumpr cam and here is my problem....he wanted to keep the stock heads couldent see himself spending 1300 dollars on a set of afr......dumb i know but yeah i built the motor but kept the stock rockers changed springs lifters and the pushrods but now i got it all together its all timed up right and i keep getting backfires its not starting either if anyone has any input i would really appriciate it..what i am thinking is it could be that he needs to buy new rockers but i dont know never kept stock rockers or heads on my builds. thx......oh and to introduce the car its a 93 lx originaly a 4 cyl but 302 now .30 over stock heads (i ported and polished them.)mutha thumper cam performer intake spacer relocation bracket no ac no smog if somone has input it would b appriciated....and i know i have horrable literature. thx

fford said:

I cant even remember how to set up stock rockers anymore! But I would say you have a valve hanging open or not seating correctly, not to assume anything, did you make sure none of the valves where bent slightly?

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yeah all of the valves are straight and here is a update i talked to the guy i got cam from it has like 5 miles on it the guy set up the car same way i did but he got the car running and he drove it to muffler shop then back home did a big harry ass burn out with it and after that it died on him coming down the road he told me that he couldent get the car to even turn over. he thought he spun the bearings turns out i got the block pulled it apart found out he broke the shaft that turns the oil pump....his oil pump was froze up becouse of garbage in the oil....dumb ass i know these are my points.....1 he didint give the motor time to break in new cam lifters 2 he dogged the **** out of it right after the build 3 he didnt have a hv oil pump on the car to begin with......yea stupid i know.....well let me know if you have ay more ideas but i think possably im just off on timing and i gas fouled the plugs im going out there to pull all the plugs now and check the compression on #1 cylinder....