QuestionI have a 1984 Chevy K 10 Scottsdale pickup with a 305 V8. I need to replace some vacuum lines and a few other things dry rotted. Is there anywhere on the Internet I can get an exploded engine diagram?
AnswerEither on the air filter housing or valve cover there should be a vacuum diagram.back in those years it was very difficult to distinguish vacuum systems and routing by using just the manual or sticker in engine compartment. It takes a level of understanding also , because of all of the complex, over complex designs, engineers came up with to afford the best results of any particular system.It will get confusing for you if you do more than a couple of vacuum lines at a time.Here is something you should know before you start.The engine serves up two different kinds of vacuum,when running[really there's three, but the third in not used much, if at all these days]These two kinds of vacuum have plenty of suction to perform there jobs.They are ,ported and manifold vacuum .Ported is used for EGR, VAC. ADV.,diverter valve on air injection.It's connection is usually low on throttle body injection, or carb.What is important to know about this vacuum is, that at idle,there will be no suction at THIS vacuum port. Only when under load does it start suction and at WOT [wide open throttle]the vacuum again falls off to zero.( The other vacuum which is rarely used these days ,is venturi vacuum. It starts out at zero at idle and it's vacuum increases proportional to throttle angle . At WOT it's vacuum is at it's strongest.)Ported vacuum- signals systems that are to function when engine is under load ,like EGR. Manifold vacuum,does pretty much the opposite. It has most suction at idle, and falls off fairly rapidly, once you crack the throttle. It was used a lot in conjunction with ported vac. to help those employed smog systems operate at more exacting parameters, and is what makes the various systems labyrinth of vacuum lines so Pandora's box-ey, when you look at them. Just remember, when in doubt, or completely lost,that,usually from what ever is not removed, you can trace back and determine if it starts out as man, or ported. Typically manifold vacuum source is a nipple or more comming out of manifold. It is not the primary vac source for EGR or VAc advance.Man vac is the vac that goes to your air filter housing, as part of the early fuel evap [EFE], for the heat stove [aluminum flexi pipe off of exh.man.]Vac purge ,for the gas tanks vapor recovery, works off man vac and ported. It gets complicated, and even though I am doing my best to explain, there is just so much sh-t worked into what was a simple system[s],what, with vacuum delay valves, and overcomplicated temperature over ride switches etc. that it falls short of really helping you. Maybe not,hope this helps. good luck.
