keg383z28

I have a 95 z28 that has recently had a 383c1 built for it from another person and now im fixing all the b.s. that he did wrong.

My question was it has headers on it w/o smog pump and emissions, i think the vacuum lines on the dist have been switched or located in the wrong place where exactly do each of the vent lines run to on the dist?

Also the pcv valve on the drivers side intake is left open should it be plugged or is it ok?

95 z28 383ci eagle crank, eagle h-beam rods, speedpro pistons, ported & polished heads 202 intakes, GMPP LT4 cam kit .525 list cam,1.6 rollers,cai w/ vortech elbow,meizere 55gpm w/p, headman headers,gutted cat.slp fan controller,jet skip shift elem.,lightened flywheel,ram clutch,6spd,and thats all i can think of right now.

69z-28

there are 2 lines to the opti for vaccum. one from the intake that goes to the opti, then one from the elbow that goes to the opti. i can check on my car tomorrow for you, i forgot which one goes to which part of the opti, maybe someone here can chime in.

PCV should never be left open...lol

shoebox

Look on my Tech Page. There are pics of everything you are asking about.

keg383z28

my vacuum line was connected to a check valve that is either plugged or the wrong valve,can i run one vacuum line from a capped fitting behind the pcv and another line to the dist? The line that was to the dist turned into a plastic line and routed to a box on the passenger side of the intake.

shoebox

It does not matter where you get the vacuum, but you need to be sure the hose to the distributor has the filter and flow reducer present. Full vacuum can cause problems in the opti. There actually may be nothing wrong with the valve you are talking about. It's not supposed to let a lot of vacuum through.

Injuneer

You need an air supply line, connected to the intake air ducting, AFTER the MAF sensor and the air filter. That flows clean, filtered, MAF measured air to the Opti. The vacuum source line needs to go from the Opti to one of the full-vacuum ports on the side of the intake manifold. The correct locations are clearly shown in the photos on Shoebox's website. Note in particular the locations on the Opti for each of the lines described above.

http://shbox.com/1/opti_vacuum_harness.jpg

keg383z28

thanks for the info this should help the progress of my car greatly its been quiet a challenge trying to find the right info thanks again!

dbrunner2

What kind of problems can be caused by applying full vacuum to the Opti? The flow restrictor on my MSD opti broke, so I just removed it from the system. I'm guessing the problems would be something along the lines of oil leaking into the Opti past the shaft seal; I haven't noticed anything that seems like it would be caused by that, but I am seeing a weird misfire that sets code 42 and occurs only when the engine's cold, between 1500 and 1800 rpm, and above about 20% throttle.

shoebox

The vacuum can cause the internal pieces to flex and distort, causing interference problems and possible destruction.

dbrunner2

Yay!

Hopefully that's not what's going on here...at least the MSD has an aluminum base, which seems like it might do a better job than the factory plastic of keeping everything in place even with full vacuum. I'll definitely find or make myself a new flow restrictor though. I'd always figured it was just to avoid possible high idle.

Thanks a lot for the possibly Opti-saving info!

Injuneer

The factory Opti base is not plastic.

dbrunner2

Oops. Been a while since I pulled my stock Opti...

shoebox

Just buy a new GM vacuum harness. They are not expensive and have everything you need.

OneShoe50

Has anyone tried routing to the inlet elbow instead of the intake manifold?

shoebox

The vent line already goes to the elbow. The other end must go to a vacuum source. (the intake tract is not a vacuum source)