Replacing a chevy 305, Con’t

I’m no emissions expert and replacing the motor in my 86 GMC with all those vacuum lines seems to be a challenging proposition for a classic car guy like me. Even though the vacuum lines are documented on the sticker in front of the radiator, I had to make my own drawing. The sticker shows the same lines but each of the devices are noted using names and acronyms that don’t make sense to me. Like I said, I’m not an emissions guy.

Luckily for me it wasn’t too complicated. The entire system seemed to be comprised of 3 basic sections. There were 2 tempurature sensitive vacuum switches controlling or regulating most of the vacuum, one on the thermostat housing and one on the intake manifold next to the thermostat housing. The third section is the vapor canister recirculation system.

I’m not going to try to decipher this for you, but I will provide a couple of drawings to help you decipher your own vacuum line spaghetti bowl. For the most part it pays to realize that each of the vacuum lines has a memory and retains a shape that will tell you where it was most likely connected when it came off the engine. As long as you don’t try to roll up the vacuum lines or shove them in a box or bag where they will develop a new memory, you should be OK.

For those of you who are obsessively forced or compelled to understand how this stuff works you can check out this article on Automotive evaporative emissions systems written at the University of Southern Colorado.

This entry was posted on Wednesday, May 23rd, 2007 at 9:29 am and is filed under Automotive day. The entry is tagged under You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.