Timing a TBI 350.

[Tigerstripe40]

This is for a 1991 TBI 350.

We had to pull the distributor out to chagne the pickup coil in the dizzy, and want to reset the timing.

Searching mud, there is no definitive answer on how to do this.

One thread says 0 dbtdc, another says 6-8 dbtdc, yet another says 10dbtdc.
What is the spec for a 1991 TBI 350?
Also, this dizzy does NOT have a vacuum advance.

Now I know that there is a wire that needs to be disconnected to disable the EST to set the timing.

Could I get some clarification?

Here is what I am thinking.

Disconntec EST wire.
Using a light, set distributor timing to 10 Degress btdc @700 rpm.
reconnect EST wire.
Drive the snot out of the beast.

Is this correct?

Also, how does one adjust the idle on a TBI 350?

Thanks!

 

[palerider101]

Help

Bump

 

[cardinal fang]

timing a SBC TBI

All TBI harness come equipped with a connector that is disconnected when setting the timing. This wire prevents the ECM from managing the advance on the TBI dizzy. The wire may be different colors depending on the manufature of the harness. It is usually located adjacent to the dizzy. When adjusting the timing, discannect that wire. Using a timing light, set the timing to 0 degrees. The ECM will take care of the running advance. You will get a trouble code when the wire is disconnected. Can't remeber what the come number is, though. Of course after setting the timing reconnect the wire. IFAIK, vacuume advances do not exist on TBI engines.

 

[Yoda]

The idle is computer controlled.

Timing is done as stated above.

When I did my TBI, I used the computer prom from a stick shift truck. The computer made it idle at 850 (no good, I have an automatic)

Got the prom from an automatic, and good to go

 

[DaveWest5150]

You didnt state what wire harness you are running... is it stock from a gm truck? or is it a painless?..... anyways My 90 sub had a Tan/light brown wire that needed to be unpluged and then you would set the timing to 0, plug the wire back in and you were good to go.
hth

 

[Tigerstripe40]

You didnt state what wire harness you are running... is it stock from a gm truck? or is it a painless?..... anyways My 90 sub had a Tan/light brown wire that needed to be unpluged and then you would set the timing to 0, plug the wire back in and you were good to go.
hth

It's stock GM harness out of either a 1991 or a 1990.
But extremely painful....


We know about the tan/white wire. We connected a semi-quick disconnect to it last night. Will timing affect the running?

This truck will run STRONG for about 90 seconds, then die.
Makes no difference if we keep on the gas.
I think it has something to do with the ignition...
Any ideas?

Thanks!

 

[cardinal fang]

If you are not getting any trouble codes, you might have fuel starvation problem. What type of electric fuel pump are you running? Are you putting the fuel filter before or after the pump?

 

[Gumby]

It's stock GM harness out of either a 1991 or a 1990.
But extremely painful....


We know about the tan/white wire. We connected a semi-quick disconnect to it last night. Will timing affect the running?

This truck will run STRONG for about 90 seconds, then die.
Makes no difference if we keep on the gas.
I think it has something to do with the ignition...
Any ideas?

Thanks!

No tach signal to the ECM = no fuel pump.

You need to disconnect the ESC wire to the distributor, not the tach wire to the ECM.

 

[Colorado Boy-74-FJ40]

I have a Vortec 350TBI Crate motor in my Chev truck. It is in a 1994 . The timing on that is 10º BTDC at 850 RPM idle. If that helps.

 

[DaveWest5150]

It sounds feul related to me too! can you hear it running? Verify you have feul pressure and let us know

 

[Tigerstripe40]

It sounds feul related to me too! can you hear it running? Verify you have feul pressure and let us know

Yes, we can hear the fuel pump running.
We can also hear the fuel pump relay clcik when we turn on the key. The fuel pump is controlled by the ECM.

The fuel pump is a holley pump from Howell. (we took a carter pump off as it couldn't supply enough fuel and got VERY hot)

Also, there are 2 fuel filters. 1 before the EFI pump, 1 after the EFI pump.

The truck has been running pretty well for the last few days.
IT will die suddenly, and if we turn off the truck until the CEL turns off, the truck starts right back up. It's only happened once or twice.
It also will idle for about 90 seconds then die. But if we drive down the road, we have no problems.

I am thinking that it might be the knock sensor, as I smacked the exhaust manifold with a hammer and did not get a CEL. Perhaps the computer is advancing the timing to try to get a signal from the knock sensor, and it advancing so much the spark can't ignite the fuel in the cylinder.