1996 gmc 4.3 distributor phase issue need help

[bracketshark]

I got called to help a friend diagnose the missfire in his freshly rebuilt 96 4.3 GMC. I carried my buddies snap on solice to help with the checkout. There was a new napa cap and rotor as well as wires installed on the motor, the cam was change to a competition cams model that was sold as basically stock. The solice showed missfires on #4 and 6 cylinders so we changed back to the old cap this missfire went away. When we tried to set the distributor phase or cam phase whatever its called, the solice showed 29degrees, we thought the distributor was turned as far as it would go so we changed the rotor one tooth in the cam and checked it again. This time we got -31 degrees. The problem is that the distributor will not turn to correct the phasing, the hold down clamp for the distributor is made and installed on the distributor such that it allows no rotation of the distributor as long as the bolt is installed. Any body fought this battle before? The truck runs but has no power, I've never seen this before. Any suggestions appreciated. Thanks

[ronaldk]

My chilton book says there are notches on the inside base of the distributor, one with 8 one with 6. That is where you point your rotor when eng is on TDC. 6 for 6cyl.Also those marks must line up with distributor fully seated. Book say to turn over to TDC once more to make sure it is in fact lined up if not lined up repeat by moving one tooth at a time. recheck until it is confirmed correct, then start veh ecm takes over the timing.GOOD LUCK let us know how you do

[Jeremy-WI]

Was the cam installed with the timing marks correct on the cam and cranks gear? You should be able to get that closer to 0 degrees, did you rev the motor over 1000rpms while checking the cam offset(or cam retard) on the scanner

[bracketshark]

I didn't build the motor, I was told the cam is installed correctly. Yes we continuously reved the motor over 1000 rpm and saw maybe 1-2 degree change in the phasing. The owner is going to call comp cams tomorrow. I don't know for sure that with the distributor in the proper location the motor can run the way it should, it runs that rough. I'll post back when we figure it out. I think the cam is wronge for the application. Thanks

[MT-2500]

Originally Posted by bracketshark

I didn't build the motor, I was told the cam is installed correctly. Yes we continuously reved the motor over 1000 rpm and saw maybe 1-2 degree change in the phasing. The owner is going to call comp cams tomorrow. I don't know for sure that with the distributor in the proper location the motor can run the way it should, it runs that rough. I'll post back when we figure it out. I think the cam is wronge for the application. Thanks

http://files.automotiveforums.com/ga...hp?photo=51302


If dist will not center up or/to the right cam retard setting remove dist and turn the dist gear 1/2 turn /190 degrees.