Will Optical bump change TDC offset if relearned?

[97GMC6.5Z71]

Will Optical bump change TDC offset if relearned?
I set my actual timing at about 3.5 in time set mode
then i have 11.1 desired and 11.1 actual timing
and the snap-on mt2500 scanner reads the TDC offset as 5.9 i've read that this scanner reads different and that -1.94 reads 5.4
so does the Optical bump change the TDC offset number too?

[97GMC6.5Z71]

I'm wondering if the optical senser bump advanced the TDC offset some but not the base timing because its still at 3.5 in the time set mode
But when i exit the time set mode my base (actual) timing and desired are at 11.1 i read it was to be about 8.5 degrees:rolleyes:

[DA BIG ONE]

Running gears or chain?

If your are running timing gears there is a 2 deg advance built into them a TDCO of -1.90 (1996 to 2001) should be max offset as per gear manufacturer. Desired and actual will show the 2 deg + when running gears.

[joed]

I think what you are seeing is pretty typical, especially on the OBD II trucks. My truck always seems to run a base timing of 13-14 - different factors/tables apply an advance to the base timing tables - they start out at 10-11 if I recall.

To answer your original ?, I think an optic bump will have a similar affect to a higher TDC offset, tending to advance the timing.

Hope that helps.

Joe.

[97GMC6.5Z71]

Running gears or chain?

If your are running timing gears there is a 2 deg advance built into them a TDCO of -1.90 (1996 to 2001) should be max offset as per gear manufacturer. Desired and actual will show the 2 deg + when running gears.

It has the stock timing chain for the cam and drive gears for the ip.

I don't think stock timing set has 2 deg advance cam or ip does it?:eek:

[Kennedy]

Will Optical bump change TDC offset if relearned?
I set my actual timing at about 3.5 in time set mode
then i have 11.1 desired and 11.1 actual timing
and the snap-on mt2500 scanner reads the TDC offset as 5.9 i've read that this scanner reads different and that -1.94 reads 5.4
so does the Optical bump change the TDC offset number too?

#1 rule: Don't believe anything but a Tech 2. Third party scanners display errant data that I do not trust. My best advice is skip the bump, and put a good ECM tune in.

[97GMC6.5Z71]

I changed the optic bump back to stock setting and my timing dropped down from 11.1 to 10.0 and i relearned the TDC off set at 6.1 then in the time set mode the base timing was about 4.5 and setting code 1214 TDC offset so i turned the ip back some and got it at 3.5 with the actul timing at 7.0-7.5 degrees and a TDC offset of 5.9 with no more 1214 code.
It starts better now and the wot smoke is more of a gray black then the pitch black i was getting:D

[JohnC]

The answer is "yes". Moving the optical sensor has a similar effect to moving the timing pointer on the crankshaft timing marks; zero isn't really zero any more.