How do I get the correct timming....HELP

[BlueOx]

I need to fix the timing on my K5 but I’m lost on how to do it right. I replaced the old 305 with a GM Goodwrench 350 and added a TBI system to it, now I need to find the correct timing. Before all I did was move the distributor until the engine ran well but, now with the TBI I want to do it right. On the old 305 there was a timing tab on the timing chain cover that I used with a timing light to get it right. On the 350 there isn’t one in the timing cover. When I replaced the old distributor with the new comp. controlled one I just placed my finger over #1 spark plug hole and turned the engine over. When I felt the air I knew I was close and stabbed it in. I also installed a timing tab that bolted on to the right side of the water pump (as you look at it) but the mark on the balancer is no where near the tab, nor does the rotor point to #1 when I line up the mark and the tab. The mark is more in the middle of the water pump. I thought the original timing tab was in the middle of the timing chain cover.

The engine does run some what well the questing way that I have it now but I need help. Does any one here have any ideas on how I should do it or what I need?

Thanks
Charles

 

[TopOff]

Ummmm you say you have an '85 with TBI?!?!?

IIRC - The 87 TBI uses a computer controlled Distributor... I am not sure if this is compatible with your 87 TBI.

The 87 TBI will need to be at 0 timing, and the comptuer takes care of the rest along with a knock sensor.

Good luck.

If nothing else, your BTT. /forums/images/graemlins/laugh.gif

 

[90K5]

Yeah, the timing for TBI's and the other ones is different. You need to unplug the an wire to set the timing, if you have one, I think its on the passenger side of the firewall.

 

[K05Aggie]

I found the wire on the far side of the brake booster in a loom with others. You can trace it from one of the connectors on the back of the distributor. I would go look right now, but the Blazer is at the tranny shop.

Where I learned this.

 

[HarryH3]

It's a tan wire with a black stripe and has an inline weatherpack connector that you unplug to set the timing. This disconnects the computer control from the distributor so that the computer can't mess with the timing while you're setting it. /forums/images/graemlins/cool.gif

 

[BlueOx]

To all that replied, I know the TBI timing has to be at zero when you unplug the wire and when you plug it in the ECM does the rest. That’s the easy part for me. I probably didn’t explain myself that well. I need to know how I find true mechanical zero. I used the finger over the spark plug hole trick and cranked the engine until the piston blew air out the hole. Then I stabbed the distributor with the rotor facing #1 spark plug. This way put me in the ball park with the timing but, with my timing pointer in the wrong place the timing marks don’t line up. I thought there was something that you could screw into the spark plug hole and rotate the crank until the piston hits the top and that’s TDC, but I can’t find any thing like that.

Charles

 

[imiceman44]

There is, it's called piston stop.
You can use anything even a bolt through the spark plug hole.
The way to do it is once you have the stop in, turn slowly until you hit mark the point, then rotate to the other side and mark, the TDC is in the middle of those 2 points.
Hope that was your required answer.

 

[TopOff]

Ahhh OK.

After you have the TDC on the piston... (via Iceman's description) or TDC on the Timing mark on the pulley...

Take the cap off the rotor, The Rotor needs to point to a scribed mark on the distributor housing. It should be the only scribed mark on the housing where the cap goes over. This is TDC #1 for the ignition.

/forums/images/graemlins/thumb.gif