I thank you in advance for your knowledge and help. I have a non-vented 1994 Z28 I'm about to install and need to know if the spline drive shaft for the opti should be put in a specific way? I know about the key-way on the splines but as I look at the shaft I'm wondering if a specific side of the shaft should face the block?? You know, just like the water pump drive coupling has a line on it that should always face the block. I was thinking does the same reasoning apply to the opti spline drive shaft?? Should one specific side of the shaft face the block?? I'm actually downgrading from a vented MSD opti because it crapped out on me and happened to have a new stock non vented opti lying around. I just needed the shaft which I just got but as I'm looking at it, it looks like it has a line towards one side so that's what got me thinking?? Thanks again for your input.

-Chris

 

The line towards one side is the key to how it slides in. It was tough for my but if you look on the motor where the opti goes with a flash light you can see the keyed side. rotate it to roughly that position and slide it in. it should slide in easy without force. and you will know you got it in correctly if all the mounting points sit flush on the motor. take your time and its no big deal. just dont force it cause it will slide right in

 

I think his question is does it matter which end of the shaft is placed into the cam sprocket and which end it placed in the back of the Opti. Both ends are splined/indexed in a similar manner.

 

Thank you Fred, you hit the proverbial "nail on the head"!!!

 

Look closely at the stub drive. Is it perfectly symmetrical? I can't say from your description, but the line you are seeing might be from where a seal rides on it.