Vacuum plumbing questions

[Chadwick717]

More newbie questions!

So I got my truck through Colorado emissions, i leaned it out enough to pass. I richened it back up, but it is not starting the same as before I leaned it out. So I decided to buy a vacuum gauge to tune the carb.

I have a 350 with an edelbrock 1406 on it.  I was looking at the carb to see where to attach the vacuum gauge (I think I'm right in that it attaches to the port on the right front of the carb if you are facing the carb) when I noticed this


The PO had joined the two ports?  I thought my distributor needed to be hooked up to one of these ports. So I looked and my distributor is just hooked up to the air cleaner.


The truck runs fine, so I'm wondering if I should even attempt to change it. Why would it be hooked up like this? 

[LTZ C20]

Well its basically personal preference whether you want your distributor to run on PORTED or MANIFOLD vacuum.  So people prefer one over the other. It also depends on what type of engine and up grades the engine has. If it's a mostly stock engine I would set it back to stock configuration.  If you notice, the port on the RIGHT side is slightly higher than the left side. The RIGHT side is PORTED and the LEFT side is MANIFOLD.

As to why your distributor is hooked to the air cleaner I have no idea except that maybe to PO was smoking wacky tabacky. The reason it's probably running good is because at the air cleaner it's acting as manifold vacuum,  same as being on the left port just further away from the source. I would return the vac houses to stock if the engine is stock.

[LTZ C20]

Also fix your fuel line at the "IN" side of the fuel filter. It appears to be attached crooked. It could break, crack or slip off and leak all over a hot running engine.

[Chadwick717]

Thanks for the info LTZ. I got some vac hose.  It is a mostly stock engine, so stock would be the ported vacuum correct? 

[LTZ C20]

First, what year is the truck and do you have emissions?

[Chadwick717]

It's a 1979 k10 and we do have emissions in CO

[Chadwick717]

Well I guess I should say I have to go through emissions every 5 years. I just passed so I'm good for a while.

[LTZ C20]

That's good, as I was looking in my 79 chevy service manuel this morning. It doesn't not directly say too which source it should be plumbed however, it does say that the distributor vacuum advance is plumbed by line that supplies MANIFOLD vacuum to the distributor and other parts.

Being that it was hooked to the air cleaner which is basically manifold vacuum,  I would hook it to manifold vacuum at the carb and if it runs the same, you should be fine.

[Chadwick717]

That's what I did, thanks for the help LTZ. 

[LTZ C20]

Your welcome.