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I'm thinking of adding the vent mod since the opti's on the bench anyway. I tried to find the threads, but didn't have any luck.
Any help would be appreciated.
Hi Ed,
I did this modification on my 94 LT1 engine, that I swapped into a 95 C4 last year. Here is the verbiage describing what I did:
...Yes, the dreaded Opti is a big reason for the amount of time it’s taking me. Thanks to lots of reading on this forum, I knew I wanted to use a vented Opti. I didn’t want to swap all the components: cam, cover, etc to use my 95 Opti, so I decided to vent the 94 Camaro Opti...
Here’s a brief description of my journey. First, I bought a new vented cap and rotor. Then I disassembled the 94 Opti, which wasn’t easy because the PO had used a bunch of RTV to seal it up. After checking the bearing and determining it was I good shape, and confirming that it has a Mitsubishi sensor, I began figuring out how to add the vent port. One article I read showed the author used plastic elbows and tees off of the bottom three drip holes. I decided to use a single elbow off the end port, and plugged the other two ports. I was so proud of my skills that I sealed up the new cap (after locktiting the new rotor screws), patted myself on the back, and prepared to install the freshened up Opti on my freshened up engine. This is where the plan started going to ****. When I mounted the Opti, it didn’t want to sit down on the mount bosses. A little investigation discovered that the elbow on the bottom was hitting the damper hub... I would need about 1/16” more room, but that wasn’t possible with the plastic elbow. Back to the proverbial drawing board.
I did such a great job sealing up the Opti, I didn’t want to cut it all apart, so I pulled the elbow out (easier than I thought). Now I needed to figure out how to get a different vent location. I decided to go it from the side of the boss where the drip holes are and intersect the empty hole where I removed my elbow. So I mounted it up in the drill press and added a regulated air hose to the cap port to blow the chips out instead of having them floatin around in the Opti. When I got the hole drilled, I used a brass vacuum port from a scrap Holley carb I had laying around. Long story short(er) it worked great and mounted up to the car perfectly. The Camaro engine came with the wiring harness I needed to interface to the Vette harness, so I should be good there.
I’m heading out to the garage now to continue my quest. With a bit of luck, I may be able to hear it make noise today. Wish me luck!
Here are a few pictures to help you visualize what I did:
Elbow epoxied into center lower drain hole - interfered with timing cover!
Timing cover interference as seen from Driver side
Another view of elbow in center hole - NO GOOD! I ended up removing the elbow and installing a steel nipple in the driver side flange, which intersects the plugged drain hole (right covered hole in this picture)
View from Driver side showing the nipple between the Opti cap and the timing cover. I used a vacuum port nipple that I pulled out of a junk carburetor. Much stronger and durable as compared to plastic.
Overall, it wasn't too difficult, and in my opinion, ABSOLUTELY necessary. The vacuum hose harness is reproduced, and costs around $80 IIRC. Good luck, and feel free to contact my is you need any more explanation. Keep in mind, this is ONE way to do this. I'm sure there are others. As you probably know, you can't just buy a new vented Optispark, because it will not match up to the 94 and earlier timing cover/cam drive set up.
I'll be reading your post from time to time as I get deeper into this mod. And thanks for offering
assistance. I'll more than likely take you up on that.
