4.3 break-in procedure questions

[VIKING_MECHANIC]

As I get closer to stabbin' the engine back into the truck, I got some questions related to break-in and initial start up.

I talked to the shop that did the machine work to it and got a answer that confused me so posting it here.
The guy that I would normally talk to, that knows these Vortec engines like the back of his hand was busy so I talked to an older man, and his responsive confused me.

I asked him about initial start up and how to get the timing as close to right as I can. I know the Vortecs are computer controlled, just making sure I can do as much as I can to make sure it runs smoothly at start up.

I asked him how I should set the distributor in the engine and get it set up correctly. The other "vortec guy" specifically told me to point the cap at the 6 on the housing after dropping it in.

This is where I got confused. The older man told me to disconnect a harness in the vicinity of the glove box that is a black and brown or black and white wire, I believe he told me. He said this is to reset the balance shaft at the computer. He said to do this before I put the engine back in, or at least before I connect sensors and grounds, I imagine.

Any of you know anything about the harness near the glove box? This being a balance shaft 4.3, what are the initial start up procedures?

Also curious from other users about different break-in procedures. What methods do you use?

 

[stutaeng]

Well, the reason you are confused about timing is that guy #2 described timing for a TBI setup. On TBI you disconnect that wire to get your "base" timing, and the computer advances timing based on that connection.

However, on the 4.3 Vortec, there is no adjustment on the timing: the distributer base does not rotate as it does on the TBI and earlier engines. The computer advances timing from the data from the camshaft position sensor. To set it basically you set cylinder #1 to TDC on the compression stroke and install your distributer such that the pointer is on firing order #6.

This is about as technical as I've seen on the description:

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[VIKING_MECHANIC]

Well, the reason you are confused about timing is that guy #2 described timing for a TBI setup. On TBI you disconnect that wire to get your "base" timing, and the computer advances timing based on that connection.

However, on the 4.3 Vortec, there is no adjustment on the timing: the distributer base does not rotate as it does on the TBI and earlier engines. The computer advances timing from the data from the camshaft position sensor. To set it basically you set cylinder #1 to TDC on the compression stroke and install your distributer such that the pointer is on firing order #6

Thanks, that makes a lot more sense. I think where the confusion came into play is that they[the machine shop] also rebuilt the engine in my 1991 S10, which also has a 4.3. So maybe the older guy was thinking I was talking about that and not my 97.

As far as I concerned, all I have to do is install the distributor, have #1 at TDC on compression and the pointer is on number 6 and it should fire right up. I'm a bit nervous honestly as it's been about 10 years since I've done anything timing related.

 

[Pinger]

Also curious from other users about different break-in procedures. What methods do you use?

Not specific to a Vortec - or breaking in valve gear but after a bottom end rebuild.
What I'll do as soon as it's drivable and up to temperature is accelerate quite hard in an intermediate gear them lift and let the rpm drop back and repeat the process maybe half a dozen times, drive more normally for a couple of miles (to stabilise temperatures) then repeat the process. After that I nurse it for the next 1000 miles (though getting progressively more adventurous with load and rpm) until changing the oil.

The reason for the hard accelerations early one is to get gas pressure behind the compression rings and force them into bedding in. The lift and coast down gives them a chance to cool and oil to wash away the debris.
For the process I wont have used the oil I intend finally using but something lesser. Because of that, during the 1000 miles since ring bedding, I won't allow the motor to run hard and hot for any prolonged period - though I may poke it again to exercise the rings.
Other's may disagree with my method but it has worked for me.