the vortec motor im building doesnt have the timing mark on the timing chain cover so how did the factory time these motors?

 

Install any reg SBC timing cover and a timing tab to match your balancer

The Vortec motor didn't have adjustable timing,the Vortec distributor apparently only fits in one direction on the intake,
computer handles all timing advance chores which is why Vortec has a crank angle sensor ( unneeded by you now ) in the timing cover
Remove the reluctor ring on the crank

 

the motors already all assembled

 

Read this http://www.gmtruckcentral.com/articles/distributor.html

set it like this then play with the actual distributor setting, until you can stop setting the "CHECK ENGINE LIGHT" ya gotta reset the light for every new setting

 

I'm going carbed lol, when I say the motor is assembled I mean the motor is set from the air cleaner to the oilpan, including the trans installed on it and sitting beside the car ready to stop in

 

Mr Gsaket, Holley, and Eldobrock all sell a crome timing tab that uses 2 of the timing cover bolts. heck I got one hangin on the pegboard in my shop If ya cant find one local.

 

same here. I bought one from summit or jegs for $1.99. looks good, sits in the exact same place as the OEM tab. I did this because i bought a new cover and it didn't have a tab. problem solved.

 

I've done 2 different types of vortec engines. One simply had a distributor lock. The distributor fit into a slot and was non adjustable.

All the others could be adjusted. As mentioned in the original post, there are no timing marks. Timing is adjusted by using a scan tool to see where the timing is. I've always used a Genesis scan tool to set the timing. Timing is set to zero and the computer takes over from there. Zero +/- 2 degrees is the requirement.

If you're not going to use an ECM then you'll need to install a timing pointer. You'll also need to degree the engine so that the pointer points to a mark on the balancer when the piston is exactly at TDC. Timing tape on the balancer is just as good as a new balancer with a groove in it.