boonie c4

I need a vacuum harness to complete my conversion from a nonvented optispark to a vented opti. On ebay these vacuum harness for the vented optispark are going for $70+ so I decided to build my own optispark vacuum harness and save some money, can this be done with parts from my local autoparts store? And if so what parts will I need to purchase or i'm better off just paying the $70?

Snipescastle2

I happen to have the check valves and some of the hose from a vented Opti spark off of a 1995 Z28 Camaro, $20.00 shipped...sound better?
Let me know.
Ben Smith

mtwoolford

you not only can make a vacumn harness...you can make a better harness...using better quality hose, and run it in a better, more protected route than the factory. good luck

mtwoolford

as I best recall the small hose is a 1/8 inch vacumn hose that runs from the opti to a fitting in the air intake tube; this brings fresh air into the opti.

the vacumn part is the large hose that runs off the opti to the intake manifold; I used 5/16ths inch fuel line and ran it all the way to the intake manifold before necking it down to the small hose that actually connects to the intake manifold...the factory does just the oposite; it uses a short piece of 5/16ths hose and 1/8th hose for the remainder.

regardless, the small hose requires a check valve just before the intake manifold; I found one of these in the generic section of all the little odd and assorted clips, fittings, and other parts.

that left only a filter to put in the 5/16th hose; a very small generic metal gas filter with 5/16th inch barbs proved ideal.

to transistion from the 5/16 th hose to the 1/8 hose only required a generic plastic vacumn line adapter.

boonie c4

i need to know where i can purchase these 2 items"check valve + inline airfilter" that are attached to the optispark to intake manifold vacuum line

mtwoolford

got everything at O'Reilly's / Kragen; believe the check valve is a generic Dorman product from the A.C. section; the small generic fuel filter I used was just hanging on the rack with the other filters

compyelc4

But doesn't that straight manifold vacuum have to be reduced. GM uses a filter / reducer which I believe the hole is reduced to a diameter smaller than a very very small sewing needle. In this way the ECM does not read a larger than normal manifold vacuum leak

Whaleman

I bet the optidoctor would sell a harness cheap.Dan

ChumpVette

Got mine with my Petris opti

https://petrisenterprises.com/produc...vacuum-harness

64Scout

As long as it's not too big the iac can compensate.

mtwoolford

I don't think "a diameter smaller than a very very small sewing needle " would be sufficient; there has to be sufficient flow to actually ventilate the Opti body; In any case the harness I fabbed up worked fine; the smallest i.d. was the i.d. of the plastic 1/8th inch hose barb (pretty small); there was no driveability or idle issues and the car passed California smog without a problem .

And yes that Petris piece is nice

compyelc4

Well that's quite a bit larger diameter than the pin hole in my GM filter / restrictor disc. However, I will remove that and see if I get good results like you have. I did briefly Hook Up full manifold vacuum to the Opti and received an almost immediate 22 pounds per square inch at the fresh air intake in front of the MAF

mtwoolford

good luck, I'd be interested in hearing about your results; for what its worth, on the earlier non vented OPTIs a fix, even available in kit form, was to glue in small 90 degree fittings in the drain holes and use small tubing to lead it into the intake manifold. Note that there was no provision for venting air into the OPTI, so what it accomplished other than pulling oil into the OPTI past the timing chain cover seal, is open to speculation. But the initial intention of any of these systems was to remove moisture, hence the early OPTIs with "drain holes"; I can attest that a late vented OPTI does a very good job of removing moisture; plus an side benefit is the removal of electrically induced ozone from within the OPTI; altogether a pretty good system.