a couple years ago i built up a 350 but had nothing to put it in, so i gave it to my brother, he pout it in a 1991 gmc k1500, he put 15000kms on it now he is giving back and i'm gonna replace the lg4 in my t/a with it, i was driving the truck to the shop, the oil pressure was good around 269kps(like 40psi) but after driving it for 10 minutes i was stopped at i light and the oil pressure started to fluctuate between 35 psi to 5psi and the truck sounded rough, once i started driving again the opil pressyre streadied where it should be, does anyone thing there could be something wrong with the motor? or maybe the TBI system on the truck is f**ked?

 

That doesnt tell us much unless you tell us what RPM the readings were at...