5.0 ?s

[bigcountry]

ok my buddy just droped in a 1991 5.0 mustang v8 and trans and its got aftermarket heads longtube headers cold airintake and dual electric fans and the volt meter he has is showing it being at almost 8 and it bearly runs we have checked battery cables and fuses and still nothing we changed the alternator once and had it checked it its fine it will run awesome for the first 15 to 20 mins but if u drive longer than that it will sputter and die and if u trun it off for awhile it will run fine again for the next15 to 20 mins then the same problem happens again any help on what this might be would be awesome what doyall think it could be?

 

[bigcountry]

ok after several days and lots of beer we think we found the problem the crank pulley is way to small compared to all the rest so the alternator cant get enough spin to power the car thats the only thing we can find wrong the alternator is puttin out enough for the truck so we hope thats the only problem and not something else
what do yall think?