unclet1

I just noticed on my'95 that there's a 90 degree vacuum nipple coming out of the top of the flexible intake hose going into the throttle body. I don't see a loose hose and the car seems to run fine. Any idea where this hose goes? Maybe a picture ? TIA

WVZR-1

I believe that the opti vacuum vent harness actually goes to the intake there.

Snapshots in this post

https://www.corvetteforum.com/forums...post1585444534

unclet1

Thank you very much. Any idea it's purpose ?

scotth48

Help remove any moisture in the optispark and reduce damage to it. Earlier LT1's did not have that and they suffered for it. Moisture was a killer on them.

unclet1

Thanks for good info. guys . I'll sure check it out tomorrow.

MatthewMiller

The hose that connects to the accordion-pleated intake hose ahead of the throttle body is not actually a vacuum hose. It provides the supply of fresh, clean air to the optispark. There is a different hose that goes from the intake (behind the throttle blade, from a true vacuum port) to the opti which provides the vacuum to draw the fresh air through the opti.

DGXR

^ correct. The main accordion air connection to the TB is of course directly from the air filter, so that is clean air. The small hose connection on the side goes to the optispark as a source of fresh air.

The vacuum supply (which sucks this fresh airflow through opti assembly) is provided by a fitting on the front of the intake manifold under the TB.
In the attached pic, it's the bottom hole in the painted black area on the lower left. There is a hose fitting screwed into this hole, the vacuum hose to the opti connects to this fitting. At least that's how it is configured on my 1995.

There are several vacuum ports in the intake manifold, each has a specific purpose (brake booster, PCV, etc)