vacuum line help

[Psyco Diver 69]

Hey I have a 84 GMC sierra 305 with a 700r4 trans with a edelbrock 600cfm carb, open element airfilter, no EGR or airpump (the belt is removed but otherwise its all there) but other wise 100% stock. My problem is my engine bay is a mess of vacuum hoses that are plugged with screws and dry rotted thanks to the previous owners. I need help on detangling this mess and figuring how to get this all set up correctly. Can anyone give me a diagrham or tell me where everything is suppose be hooked up too and what I acctually need and don't need?

[Psyco Diver 69]

Nevermind, after some searching I figured out all I really need is a line for my vacuum advance and a line for the low vacuum switch for the trans. The TC locks up alot better now, it used to engage sometimes when I floored it since the lines with dry rotted

[civiclifer]

Nevermind, after some searching I figured out all I really need is a line for my vacuum advance and a line for the low vacuum switch for the trans. The TC locks up alot better now, it used to engage sometimes when I floored it since the lines with dry rotted

Where did you find the info?

[Dr_Snooz]

Yeah, with an aftermarket carb, it's pretty straightforward. You need vac for the distributor, PCV and brake booster. Everything else can go. Unless you need to pass smog. Then it all gets a lot more interesting.

[9511234]

I'm going to need to simplify my vacuum lines, too.

I have to pass a smog test that it is there... but I know some places.

Most vacuum diagrams can be found on the front of the engine bay - there is a 3 digit code for each one. 

If you at least can see that code or if the sticker hasn't been removed, there is always the option of looking at a repair manual.

There are multiple vacuum configurations for California, high altitude, and regular configurations listed.  I think there are 15 pages of vacuum diagrams from the different engines and years in my repair manual.

[Dr_Snooz]

Sorry, just getting back to this one. If you have to pass smog, the sticker on the air cleaner tells what smog controls were installed on the car at the factory (EGR, AIR pump, cat, etc.) For the California smog check, at least, the tech is supposed to ensure that those smog controls are installed and hooked up. They are also supposed to make sure that all aftermarket modifications have CARB numbers, the smog controls are functioning properly and so forth. That's the requirement, but practice is somewhat different. If you can't figure out the vacuum routing, I assure you no smog tech is going to take the time. In most cases, the tech makes sure that what's listed on the air cleaner sticker is still there and that it appears to be hooked up. If you can do that much, you will pass the visual portion of the test. I'd recommend making sure that all those things actually work too. Why pollute the air if you don't have to? After that, you just need to make sure that it blows clean at 15 and 25 mph and you're good. A wideband O2 sensor will be enormously helpful in this regard so you can get the tune dialed in at those speeds. I bought a narrow-band sensor for my truck and it was $135 I might as well have flushed. It's completely useless. I resorted to sniffing the exhaust and tuning until it smelled right. If you get the A/F ratio right, then your HC's and NOx should be in proper balance (assuming you have the EGR system working properly). High CO's are just a matter of keeping things maintained and clean (good oil, good gas) and you should be able to pass.

It ticks me off that California is so obnoxious about their smog laws. They are so fixated on junking old cars that people don't even bother trying to pass. They just go buy an illegal smog. If California were somewhat sensible, they would have a better impact. If they were going after the auto-makers with the same enthusiasm, I'd be more understanding. Instead, they cave on CO2 emissions due to automaker lobbying, but the poor people who are just trying to get their old cars to work on time bear the brunt. Nuts to California. Anyway, I'd say, if you can blow clean at a valid smog check, you should, even if you aren't technically legal in every way CARB wants you to be. It's better than an illegal smog,

Finally, if you aren't sure you'll pass, request a pre-test before doing the real test. A pre-test will give you your numbers without reporting them to the state. That can be a real life-saver if you happen to go gross-polluter.

Good luck.