I am building an early version Opti, but trying to build a vented version. The unit doesn't have an air inlet actually since the body is still a sealed unit - the dist. cap is vented. Not the best case, but an improvement over non-vented? Should I add an air inlet let? by drilling the unit and adding a port and where?

Anyone else done this?

Yes, I know this is a dead horse that I'm beating.

Does this still hold true as best case - http://www.superchevy.com/how-to/16758/

 

Why not just buy a MSD vented unit?

 

I'd rather buy the MSD but $$$$ prevents it. I have also looked at the DragonFire unit.

I bought an Cardone unit years ago and they replaced it under warranty. The base unit is brand new (rebuilt). The cap is a separately purchased vented unit.

 

I think maybe I'll add one inlet vent and seal the other two drain holes which are useless anyway.

So, a vented early opti on a budget... One change I may make however is to add an inline filter on the supply side to be sure that no dirt gets into the unit. A little added insurance??.

 

I just put a couple of vacuum tees and vacuum line and used the vented gm lines

 

MSD cap kit adds venting and is competitively priced. He wasn't suggesting the whole unit.

 

This is the finished opti that I completed last night using a stock (reman) spline drive opti and aftermarket cap/rotor.

Early version Opti converted to a vented unit. New harness heat shrink connection. Silicon in the two remaining weep holes. The nipple shown pointing to 6 o'clock position is for the high vacuum side and the other from the cap to the low vacuum side. Also loctite was applied to the rotor screws.

Variation from the factory vented opti is that the fresh air inlet is located on the bottom of the unit rather than the top. I'm also considering adding a filter to the fresh air inlet side to further prevent any debris from entering the system and not plumbing this into the air inlet system. I will be adding a fitting ahead of the MAF sensor. This will prevent any change in the airflow at idle but hopefully produces enough vacuum to be effective.

This is my best attempt at an opti that will live for a while...

 

that looks like it will come awfully close to the crank hub

 

Heres how I do mine. I need to update the how-to in my sig, way overdue.

I selected the location for the top fitting to emulate the location on the isolator that MSD uses for its cap in the 8481 kit. It doesn't interfere with the location of the water pump coupler or the opti harness. I switched to a single straight vacuum fitting on the cap (bottom). Less complicated than my original. I got the first vacuum harness from a Cadillac Fleetwood in the local boneyard for $2.00. I bought a new one for a pretty low price of $30.00for the car in my sig. For both, I trimmed the vacuum harness a little bit to get a better fit, since the top port on the isolator is a different location (shorter distance) from the location on factory vented setups from 95-on.

EDIT: I ditched the MSD vacuum harness because it split & rotted after only 2 years.