I just put a 5.3l in my truck, I assembled myself clearances were fine ive got the o-ring on my pick-up tube and the engine has all new bearings, im running 5-w30 and on cold start up I have almost 40psi once it warms up to operating temps its right at about 20psi and stays there while driving unless I hammer down on it then it goes to almost 40, I feel like the 20 psi is low for driving down the highway? My 4.8l had 40 psi while running down the road and 60 when I crammed on it.
And second my truck drops rpm when I do something like roll both windows up at the same time and move my gear selector from p to d to fast, its not just the average lights dimming a little bit I have killed the truck while idling by doing this, I just took it for its long first drive tonight so I haven't looked any further into things.

thanks for the help!

 

had to run to town, on the way back truck was stuttering and cutting out, it ended up dying, I got it started and rushed it home as it continued to do the same thing and died another time, pulled p0102 MAF circuit low input, p0440 evap control system malfunction, and p1153 ho2s insufficient switching bank 2 sensor 1

 

now the truck wont even stay idling, it only starts if I pump the throttle, and when it does start it wont stay running unless you keep giving it throttle, and even then it cuts out and pops and stutters etc, I replaced my MAF (after testing for voltage and ground) and 02 sensor, I also switched computers, this time it would stay idling but sounded like I had a fat nasty cam and was obviously giving me the classic p0300 code, anybody have any idea?

 

Did you check all your grounds to engine and to frame?

 

Yea I couldn't find anything left of or loose but) hat doesn't mean I still didn't miss anything, I'm wondering if it could be computer related

 

well I figured id update, found the problem and I cant believe I over looked it, the ground strap from the firewall to engine was off and laying behind my brake booster, after I bolted that on the engine I started it up and it fired right up, I was still getting a random cylinder misfire code and you could here it slightly missing, I checked my plugs and they were pretty black so I decided to change them after the change still the miss, I brought it into the garage and and the mis started to sound worse, I pulled the pass. side valve cover and found nothing all the rockers were moving, i moved to the drivers side and found a rocker arm with the tip exploded, keepers laying there and the spring still over the top of the valve stem, i had to use a "beating device" to even get the valve to move, gonna bring a scope home tomorrow to see if the piston is cracked or broke.

 

Ouch...