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94 opti spark vent conversion

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  • 94 opti spark vent conversion

    I know its been done before. But here is how I did mine.
    First, I am not completely finished with it I need to figure out a way to duplicate the orifice function of the original, orifice/filter.
    Ok, I never really cared using epoxy on my distributor to hold in the vent tube. It just didnt feel solid to me. I needed to figure out a way to add the tube and not worry about it. So I needed some form of a pressed in or threaded fitting. I used to build and fly R/C airplanes so I have lots of brass tubes and such laying around, so I thought I could just press one in and use that. Believe it or not thats not as easy as you would think. After a couple of failed attempts to get a hole the correct size to press in a piece of brass tubing. I decided that maybe a threaded fitting was the way to go. I started looking through some of my modeling parts and came across this.

    Its a through bulkhead fitting for fuel lines.

    These are available at better hobby shops. Or a drilled out zirk fitting may also work.
    These were metric threading and I got lucky and had the proper tapon hand. So I tapped out the right hand hole in the dist. case to accept this bulkhead fitting and loctited it in place. I then tapped the other 2 holes and installed 2 6-32 screws to seal them up.
    As seen here.
    And here.

    Next time I will use set screws. The head of the middle screw hit on the raised area of the crank seal. I ended up filing part of the head down for clearance.
    There isnt a lot of clearance with the crankshaft so I chose to use the far right hole for my vacuum line and the cap for intake air.
    I also spent a bit of time with some silicone and loctite on the distributor. I opened it and found the rotor screws looser than I would have liked and no loctite on them. Quickly remedied. I sealed the 2 halves of the Opti also. The area around the plug is fairly open. The seal is only keyed on one side so I silicone the whole thing nice and tight.
    It seems to hold a bit of vacuum so I know it should remove any ozone once it is up and running.

    One other thing to note. GM designed their system to use a orifice to control how much vacuum this system utilizes. I dont have access to an orifice. So I need to figure out a way to limit the amount of vacuum used by this vent. Step one was to only use one of the 3 holes in the opti base. If that isnt enough I will use a piece of plastic line with a very small hole in it inserted into the vacuum line. I dont want it to act like a vacuum leak so some form of limit will need to be used.
    I will try to get some more pics once the entire system is in place.

  • #2
    Alrighty !!!!! iTS ALIVE!!!! The opti spark modification seems to function as I hoped. I pinched off the vacuum line at idle and opened it , no discernable change in rpm's. So I think it is working ok as is.

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    • #3
      caution, and note to self: Do NOT pinch off the intake side of the vacuum vent system. You can collapse the cap and damage it.


      I found an "orifice" today at the bone yard.

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      • #4
        Be very thorough when cleaning the shavings out of the unit after tapping it for threads. I missed a bit of shavings and the car ran like crud. I ended up with a new msd unit before we figured out what the problem was with the modified rich porter. Somehow some shavings were left inside after blowing it out.

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        • #5
          Originally posted by zeeman View Post
          caution, and note to self: Do NOT pinch off the intake side of the vacuum vent system. You can collapse the cap and damage it.


          I found an "orifice" today at the bone yard.

          Wow, orifice and bone in the same sentence and not one comment? ya'll are slippin'.

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