95-96 optispark vent hose routing
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Joined: Oct 2013
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95-96 optispark vent hose routing
Does anyone have a vent house routing diagram from a 95-96 FMS for the optispark. I have a 93 that I am putting a vented cap on and would like to see where the lines are routed from the factory on the later vented systems. Thanks for any info.....
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
DON'T run rubber only vacumn hose; get quality reinforced fuel line hose; cut it extra long and run it as far away as possible from serpentine belts, etc.
This is one place you can definitely improve on the OEM setup.
Melting Slicks
Joined: Jan 2009
Posts: 3,482
Likes: 196
From: folsom california
the small fitting on the opti runs to the bellows in front of the throttle body; the hose goes to a small, 1/8 th inch (?) fitting that pugs into a hole on the side of the bellows; it could go anywhere convenient; its purpose is to deliver filtered air to the opti.
the large fitting is another issue. It runs, eventually to a small fitting on the driver side of the intake manifold. Now this is where it gets interesting. The fitting on the opti is 5/16ths; the factory harness is immediately necked down to a smaller hose that runs up to and along side the valve cover / intake manifold; then through a filter, then a check valve, then into the intake manifold.
I chose to run 5/16th fuel line hose from the opti up to and along side the valve cover / intake manifold. The factory filter is a (very) small, plastic affair. For a filter I chose a small, generic metal fuel line filter (still larger and more robust than the factory filter), after the filter, I reduced it down to 1/8th inch (?) hose; good luck finding a factory check valve, but a generic check valve, usually associated with air conditioning and HVAC, is the exact same thing.
There maybe an "opti harness", as this whole affair is referred to in GM speak, out there somewhere, but again this something you can fab up for yourself
the large fitting is another issue. It runs, eventually to a small fitting on the driver side of the intake manifold. Now this is where it gets interesting. The fitting on the opti is 5/16ths; the factory harness is immediately necked down to a smaller hose that runs up to and along side the valve cover / intake manifold; then through a filter, then a check valve, then into the intake manifold.
I chose to run 5/16th fuel line hose from the opti up to and along side the valve cover / intake manifold. The factory filter is a (very) small, plastic affair. For a filter I chose a small, generic metal fuel line filter (still larger and more robust than the factory filter), after the filter, I reduced it down to 1/8th inch (?) hose; good luck finding a factory check valve, but a generic check valve, usually associated with air conditioning and HVAC, is the exact same thing.
There maybe an "opti harness", as this whole affair is referred to in GM speak, out there somewhere, but again this something you can fab up for yourself
Last edited by mtwoolford; Nov 13, 2013 at 08:36 AM.
Le Mans Master
Joined: Jul 2005
Posts: 5,193
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And don't forget to connect a hose to the weep hole on the bottom of the water pump..and get it clear of the opti. I used a small brass fitting which i cemented into the hole...just another trick the engineers didn't figure out.
Safety Car
Joined: Jan 2006
Posts: 3,940
Likes: 43
From: shavertown Pa.
You can run some hard plastic tubing(1/4") up to the bellows, after connecting it on the dist. cap with a small length of hose, run it behind things to keep it out of the way of the belt.
Then punch a smaller hole in the bellows and force the plastic tubing thru then seal it with silicone, aim the tubing toward the front.
I ran another length of tubing from the weep holes up to a vacuum source, I used a brass T reduced to 1/4 and got my vac source off the power brake line.
Then punch a smaller hole in the bellows and force the plastic tubing thru then seal it with silicone, aim the tubing toward the front.
I ran another length of tubing from the weep holes up to a vacuum source, I used a brass T reduced to 1/4 and got my vac source off the power brake line.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
I don't have a close up shot;
In this photo you'll see two hose's that are clipped to the A/C bracket, the short hose with an air filter attach's to the Nipple on the forward side of the Plenum below the Throttle body..
this photo shows the opposite hose connecting to the Bellows fitting..
I don't remember were these hose's connected on the Opti it-self?
In this photo you'll see two hose's that are clipped to the A/C bracket, the short hose with an air filter attach's to the Nipple on the forward side of the Plenum below the Throttle body..
this photo shows the opposite hose connecting to the Bellows fitting..
I don't remember were these hose's connected on the Opti it-self?
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