Vacuum line connection locations for '85 C20 with AC

[genejohnson@earthlink.net]

I'm a newbie here, first post.

Put a crate 350 in y '85 Scottsdale.  It has AC and a th400 and Ca. emissions crap.  All stock.  My AC controls (and heater, defroster, fan) don't work and I find the vacuum reservoir "ball" has a line going through the firewall but the other line is cut.  What and where is it supposed to connect for a source? 

There are a couple loose wires, too, and I'll get to those after these parts are fixed.

Also, there's vacuum line from an actuator on the passenger side exhaust manifold that connects to a weirdly U shaped steel line then another small ID (1/8") hose that is cut.    Must get vacuum from intake or carb (stock 4 barrel Holley).  Where and what does that connect to?

I printed schematic diagrams but they don't give specific locations and code stuff with numbers, not any part names.  I don't want to drive it with a vacuum leak, so it just sits until I sort those things out.

[Henry]

Hi Gene:
Take a look at this link to Autozone:
https://www.autozone.com/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528004c3cb#

Scroll through all the vac/emissions diagrams till you find yours. Do you still have a decal somewhere in the engine bay that has a two or three letter code for your hose routing?...this would simplify to determine which is your diagram.

All the vacuum power for accessories such as the A/C and brake assist originates at the intake manifold...older squarebody trucks had a port on the intake behind the carb where the vacuum was tapped off...your newer squarebody is probably the same but you will have to study the tangle of spaghetti.

The strange mechanism at the back of the engine on passenger side is probably the heat riser for timed/quick engine warm up: a flapper valve in the exhaust pipe is controlled by a vacuum signal from the carb...I believe. Your diagram should show this.

Nice looking original truck...I like the color!

Regards,
Henry

[genejohnson@earthlink.net]

Thanks Henry, but that's for emissions tubing- not HVAC lines. 

I finally found some 1/8" replacement tube at O'Reilly's, but only 3' in a sealed pack so I hope it's correct. I think that line actually goes to windshield washers.  It breaks at a touch and appears to go up the wiper arm on one side and is absent on the other.  The other end must go to the bottle although there's something that size through the firewall  (*)to some where. That's why I thought it was heat/AC controls.  VWs and Audis have colored tubes all over the place that look to be that size. Next time I'm shopping at Pick'nPull, I'll grab some of that. 
 
1)Still open question though - is the vacuum lines from the activator at the exhaust manifold passenger side.  where does it get vacuum from?  Back of carb? Diagrams I've found just say "source". I've looked at hundreds through Google.  Nada.  There is a port back there on on intake manifold,vertical, between dizzy and carb, but it has 2 lines both in use.  Some diagrams show something that appears to be horiz. from back of carb.  That's possible from seeing that type on British SU carbs.  The end of the (E) hose ends in a blob of melted plastic that reaches as far as middle of Pass. valve cover , maybe a tee?

2) I found a tee on Drivers side that has tiny 1/8" tube and one other vacuum size - both broken -maybe the thin one goes to center of firewall (*)?  or wipers?  Maybe the larger ID line goes to Pass. side exhaust manifold?

Next step may be finding another  Square to look at - through Craigslist if no one here can help.  I've gotten no useful responses from two other Squares forums.  I can't get, or see, any useful photos on line.

Thanks f0r any help!

[Rapid Roy]

Welcome.

[genejohnson@earthlink.net]

Thanks!  It's nice to find such a great site!
Fmly:
'54 ex PacBell Chevy pickup - twice owner, stripped pain(t) with used brake fluid, brushed with red zinc oxide primer, 12 volt (LOUD horn!)
'58 ex Army Big Window 1/2 ton- stayed OD
'91 2500 4x4 long bed extended cab
Now:
'85 C20 long bed, 2WD Scottsdale bought 2011 with 25k miles(Carfaxed). 350 th400, 14 bolt FF, camper rated.   New now: All rubber, All tires, starter, Alt, radiator, CD & speakers, Class IV hitch, Headache bar, rear step bumper,  AC updated.  Ranch Truck.

[Henry]

Hi Gene:
HVAC vac power source: OK, in the most straightforward scenario (pre-1980s emission spaghetti), the vac tube coming out of your firewall goes to the plastic vac accumulator tank. Then a tube goes from the vac accumulator tank to the intake manifold port behind the carb (the other line from the port goes to the transmission). So now you have a truck that is mid-1980s with all the spaghetti and the vac source port on your manifold only has two connections. If one connection is to the transmission, the other must be for your emissions and HVAC. So after the intake port, one of the lines(most likely the non-transmission line) must have a line tee: one side of the line tee goes to the vac accumulator and the other side of the line tee must go to your emissions...most likely to your TVS valve which controls vacuum to various engine emissions devices. The TVS valve is typically located on the front pass side of the intake manifold.

EFE vac power source: The flapper valve at the intersection of the pass side exh manifold and exhaust pipe should get its vac power from the TVS valve...you will see this on the emissions diagrams I directed you to earlier...you should be either figure 96, 97, or 98. The TVS valve is a thermostatic valve that controls the EFE flapper solenoid based on engine coolant water temp.

You can go to the 1984 service manual in the tech section of this website and see short descriptions of both these things I am discussing: pages 1B-7, 1B-33, and 6E8-151. I cannot find a 1985 service manual but 1984 should be the same in these respects. Unfortunately I dont think there is an overall diagram anywhere showing what your vacuum hose routings all are or how they connect to the emissions hoses. It would be beneficial if someone else on this forum would chime in or if you can locate a original 1985 truck to see how everything connects.

I recall you stating you had a Holley brand carburetor...if so, this is not original to your truck...I believe all carbs for the 73-87 350 V8 trucks were made by Rochester (or Carter) and your carb should have originally been a M4ME or M4MC Quadrajet. The Q-jet very likely has different vacuum connections to a Holley aftermarket. Does your truck have the computer control (CCC) system?

Windshield wiper/washer hoses: I dont think you have any vacuum lines going to your windshield wipers or washers...just water hoses from the wiper/washer pump to the squirters. No vacuum lines to the wiper/washer pump...just electrical connection.

Regards,
Henry

[genejohnson@earthlink.net]

Thanks Henry, once again.  It sure helps with the spaghetti!  I think I've got it correctly set up now but have yet to test to HVAC  to see if it works (forgot to do that I was so excited just to have connected the hoses.)  NOw I think the diagrams will make more sense too.
   
The tiny lines are connected to tee from a bigger lines from(to ?)vacuum ball.  The ball has only one tube.  I didn't find my engine code on Autozone site but got the code wrong just going from truck to the house.  I'll check again. XHH not XXH.  Well it runs better than ever, regardless.  I'd over heated badly 3 years ago because he radiator was plugged and I was hauling abou a on of gravel up a hill on a very hot day. I put in a crate 350 using a Craigslist mechanic who had to quit after removal. Got a different guy to put it in which led to this confusion. The crate has 85 ore HP than the stock, same torque.  I had carb rebuilt professionally locally- it's a Quadrajet which I thought was Holley my bad.  I'd had carb problems from prior sitting and previous owners work, including using silicone instead of gaskets.  Even I know that doesn't work!  It jells up & clogs stuff. Air cleaner was even glued down.  All is goodnow I think  If not there's a retired mechanic I found down my road whoknows old Chevys and maybe he can help sort out anything else. He reset my timing because I had to use the old crank pulley with a different TDC mark. 

[Henry]

Hi Gene:
If you have further trouble sorting through the vac hoses, post two pictures of your engine and this will help people see what is going on to help you out. One picture of the pass side of the top of engine and one pic on the drvr side of the top of the engine.

Once you have all your hoses connected properly, the most critical thing to keeping your truck running OK is to make sure you dont have any leaks through these vac lines as they all end up at the carb. Even if your emissions components are not working this should not cause problems...leaking vacuum lines will. Even if your EFE flapper valve is not working (either a broken solenoid or TVS) it should not be a problem since there is a spring to keep the valve in the normally open position which allows a free flow of exhaust.

Silicone and glue on carb and air cleaner...yikes!

Regards,
Henry