GM 350 vortec help

N

Nurse

Member
Not Scout related but could use the help. This site has always brought great advise.

Run of the mill Chevy 3/4 ton 4x with 350 vortec, auto, 140k. A friend bought the truck cheap because the truck wasn't running right(missing, no power, backfires).
He has replaced engine sensors, injectors, fuel filter, fuel pump. Also had the heads rebuilt. Pulled the cam out yesterday and all cam lobes are equal and look great, as do the roller lifters. Put the cam back in, and triple checked cam/crank in time. Adjust valves, replaced intake gasket ect... And the truck fired up with the same bad miss and backfire through intake, then stalled and will not fire. He has the snapon scanning tool to set timing, but couldn't keep it running long enough to set. Tried adv and retard the timing with no luck. Has even, strong compression on all cylinders.

Thoughts? Any help would be appreciated.
 
Last edited:
Is this vortec a throttle body or multi point injected setup?

Also could you tell us the year of truck.

Is the ignition a coil per plug arrangment or does it have a distributer?

Either it is going lean the ignition is missing the whole point. :lol:
 
It's a 1998 pickup with the standard throttle body on top of the plastic upper intake and the multipoint injection underneath.


The problem is, it has a horrible miss and backfires through the intake when opening the throttle. Doesn't run well enough to pull into the shop bay.

No vacuum leaks that we can find. Great compression. Timing should be close enough to run decent. Fuel pressure is wnl. I don't know if it's something in the dizzy, or maybe the computer. We took the computer out of my personal pickup(same year, same engine) with the same bad luck.....

Thoughts?
 
If it were in my driveway, first verify plug wire locations after verifing #1 tdc and if they were correct I'd buy a cap and rotor.
 
Did you know the "ignition timing" is not adjustable? The way to do it is adjusting the "cam retard offset" with the scan tool. @ 1000 rpm -if the reading is negative go clockwise with the dist to zero , if positive go counter clockwise. The snap on scanner will work fine. Hope you didn't already know all this good luck
 
sotis said:
did you know the "ignition timing" is not adjustable? The way to do it is adjusting the "cam retard offset" with the scan tool. @ 1000 rpm -if the reading is negative go clockwise with the dist to zero , if positive go counter clockwise. The snap on scanner will work fine. Hope you didn't already know all this good luck
Click to expand...

Yep, have the snap-on scan tool. Finally got it running. Was a combo if worn dizzy and two bad plug wires.:eek: thanks for all the help.
 
You must log in or register to reply here.
Back
Top