C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

Help with opti vent hoses

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Old Nov 6, 2017 | 09:31 PM
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Default Help with opti vent hoses

I installed a new opti with a vent system. Since my car is a 92 this was not there from the factory. I have it connected but there are some issues.

1) the red filter prevents installing the injector cover.
2) The hose is 1/8 vacuum but the fittings on the filter, check valve and tee are 1/4.

I was thinking of inserting a 1/8 to 1/4 union and extending the hose so the filter and check valve fit in the area aft of the pcv valve.

But I'm open to suggestions.

The factory vacuum tee is circled in blue, it was attached to the fitting circled in green

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Old Nov 7, 2017 | 03:54 PM
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I cannot comment on hose fittings or connectors for your upgrade, but I do know that the Optispark vent system is an open system - the factory systems are exposed to the atmosphere through the intake tract. This is required in order to draw fresh air through the distributor.

So if you connect the vacuum side of your upgraded opti to other parts of the intake manifold vacuum system, you may have issues holding a vacuum for those systems that require it.
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Old Nov 7, 2017 | 04:06 PM
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This works the same way. it's hard to see but the intake hose from the air intake to the opti is on the left just above the alternator.


There is only one vacuum fitting on the drivers side and the connections are per the MSD instructions for the kit. The problem is where the red piece ends up.
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Old Nov 7, 2017 | 05:16 PM
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since I'd be damned if I'd pay for an oem vacum harness, I fabbed up my own with more robust and longer hoses which allowed me to run the "harness" safely away from the serpentine belt that cut the original.

[B][/now as to the filterB], I got the smallest, off the shelf inline fuel filter I could find; it tucked nicely underneath the injector cover; the check valce was an off the shelf check valve from a Dorman display in the A/C section; looked identical to stock
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Old Nov 7, 2017 | 09:33 PM
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Can't you just run the vacuum line on the other side of the alternator bracket and position the red filter next to the injector?
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Old Nov 7, 2017 | 10:23 PM
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Originally Posted by STL94LT1
Can't you just run the vacuum line on the other side of the alternator bracket and position the red filter next to the injector?
I thought about that but that puts it in with the throttle lever. That's why I ran it with the cable under the bracket.
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Old Nov 7, 2017 | 10:27 PM
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Originally Posted by mtwoolford

now as to the filter, I got the smallest, off the shelf inline fuel filter I could find; it tucked nicely underneath the injector cover; the check valce was an off the shelf check valve from a Dorman display in the A/C section; looked identical to stock
I was wondering about using a different filter the one that came with the opti looks like it's from a briggs and straton mower.
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