| Vacuum Lines [message #142414] |
Mon, 05 September 2011 00:17  |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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Anyone got a good photo of where everything connects to the vacuum stuff? I'm thinking I have the modulator connected wrong, as the tranny doesn't quite seem to shift right. All the diagrams I find out there are no help. I took this all apart so many months ago, and some of my labels disappeared, and I cannot find the photos I took. It probably wasn't connected right anyway.
a good shot of the intake and carb from above without the air cleaner would be a great help.
I did not reinstall the Throttle return thing, as it seems silly and was cracked anyway, Nor did I reconnect the thing with the big spring at the front Left by the alternator.
All I have reconnected is the TVS, Trans Modulator, and Distributor Advance, along with the other useless heat door on the air cleaner. The DIst advance does change with vacuum (tested this), so I am in the ballpark.
The Service manual is pretty useless too.
Thanks.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: Vacuum Lines [message #142416 is a reply to message #142414] |
Mon, 05 September 2011 00:55  |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| Chr$ wrote on Mon, 05 September 2011 00:17 |
Anyone got a good photo of where everything connects to the vacuum stuff? I'm thinking I have the modulator connected wrong, as the tranny doesn't quite seem to shift right.
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On my '74 the trans modulator connects to a vacuum tap on the manifold just forward of the carb. Note the metal line must have an UP loop, similar to a plumbing trap but pointing up, and a restriction before going to the trans. Pictures tomorrow (camera is in the barn with the GMC).
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Vacuum Lines [message #142525 is a reply to message #142416] |
Mon, 05 September 2011 20:44 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| midlf wrote on Mon, 05 September 2011 00:55 |
On my '74 the trans modulator connects to a vacuum tap on the manifold just forward of the carb. Note the metal line must have an UP loop, similar to a plumbing trap but pointing up, and a restriction before going to the trans. Pictures tomorrow (camera is in the barn with the GMC).
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Pics posted. If you have any questions after reading the captions, just ask.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5885
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Vacuum Lines [message #142534 is a reply to message #142414] |
Mon, 05 September 2011 22:18 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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Thanks a bunch. That looks about like what I have. I have two ports on the back top of the carb. any photos on where those go? They all seem to differ a bit. I currently have capped them.
I do have a port on the manifold behind the carb that goes to the air cleaner, another one that goes to a hard plastic line that appears to be the vac supply to the hvac controls in the dash.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: Vacuum Lines [message #142554 is a reply to message #142525] |
Tue, 06 September 2011 00:16 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| midlf wrote on Mon, 05 September 2011 18:44 |
| midlf wrote on Mon, 05 September 2011 00:55 |
On my '74 the trans modulator connects to a vacuum tap on the manifold just forward of the carb. Note the metal line must have an UP loop, similar to a plumbing trap but pointing up, and a restriction before going to the trans. Pictures tomorrow (camera is in the barn with the GMC).
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Pics posted. If you have any questions after reading the captions, just ask.
http://www.gmcmhphotos.com/photos/showgallery.php?cat=5885
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Ken H. you are not! (He uses a labelmaker.)
IIRC there is also a loop (moisture trap) at the bottom of the metal line before it goes to the modulator. It helps to protect the modulator from freezing... and blowing the tranny up!
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Vacuum Lines [message #142650 is a reply to message #142534] |
Tue, 06 September 2011 21:05 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
Karma: 1
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Senior Member |
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| Chr$ wrote on Mon, 05 September 2011 22:18 |
Thanks a bunch. That looks about like what I have. I have two ports on the back top of the carb. any photos on where those go? They all seem to differ a bit. I currently have capped them.
I do have a port on the manifold behind the carb that goes to the air cleaner, another one that goes to a hard plastic line that appears to be the vac supply to the hvac controls in the dash.
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As for the ports on the carb I really goofed up there. When I pulled the carb to send to Dick Patterson I carefully marked the lines I pulled off. Duh - labeled where the lines went, and are still connected to, not where on the carb they connected.
You are correct on the lines to the air cleaner, for the intake air heating system, and to the HVAC.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: Vacuum Lines [message #142651 is a reply to message #142650] |
Tue, 06 September 2011 21:33 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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| midlf wrote on Tue, 06 September 2011 21:05 |
| Chr$ wrote on Mon, 05 September 2011 22:18 |
Thanks a bunch. That looks about like what I have. I have two ports on the back top of the carb. any photos on where those go? They all seem to differ a bit. I currently have capped them.
I do have a port on the manifold behind the carb that goes to the air cleaner, another one that goes to a hard plastic line that appears to be the vac supply to the hvac controls in the dash.
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As for the ports on the carb I really goofed up there. When I pulled the carb to send to Dick Patterson I carefully marked the lines I pulled off. Duh - labeled where the lines went, and are still connected to, not where on the carb they connected.
You are correct on the lines to the air cleaner, for the intake air heating system, and to the HVAC.
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Here is a photo showing how one of the ports on the back of the carb was used -- air intake for the choke heater...
http://www.gmcmhphotos.com/photos/showphoto.php?photo=16309&cat=4420
Since you have an electric choke, just cap both of them.
Dennis
Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: Vacuum Lines [message #142655 is a reply to message #142650] |
Tue, 06 September 2011 22:29 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| midlf wrote on Tue, 06 September 2011 19:05 |
...
As for the ports on the carb I really goofed up there. When I pulled the carb to send to Dick Patterson I carefully marked the lines I pulled off. Duh - labeled where the lines went, and are still connected to, not where on the carb they connected.
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How about this:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=12520
Note: I labeled the picture back when I did not understand why things where the way they where. Ported Vacuum is plumbed the the x-mas tree (I think it is called a TVS?) along with manifold vacuum, then the output is sent to the vacuum advance of the distributor.
If I understand it correctly: The TVS(?) normally routes ported vacuum to the distributor to advance or not as needed. If the engine gets hot, into the "overheated" range, it will apply manifold vacuum to the distributor vacuum advance setting the timing to help the engine cool down.
So... the TVS(?) seems to be good thing to have.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: Vacuum Lines [message #142659 is a reply to message #142414] |
Tue, 06 September 2011 23:45 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
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Senior Member |
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Thanks guys, for all the pics and help. I totally forgot about the vac to the choke which i no longer there.
Took two attempts, but passed IM240 emissions today. Passed all the loaded tests initially, but since I forgot to tweak the idle, I failed it just barely. Cranked it up to 1000 RPM in Drive, passed. If you are failing at idle, do this and remove the air filter element from the air cleaner, and you will pass. I learned the air filter bit with my 1987 mitsu pickup which still had a carb.
Only problem is that since it was so darn hot, she dieseled at shutdown. Had some vapor lock today due to barely any fuel in tank. I don't like to keep gas in the coach when it sits for a while. This was my first experience with vapor lock.
The Alum crossover seems to be working fine and leak free. Oil consumption appears normal, but didn't drive far enough today to really tell. The carb does still boil, however, you can hear it after shutting down. I run a 180* Thermostat.
Throttle response has been good except when I was having the vapors. Maybe next year I will install in-tank pumps.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: Vacuum Lines [message #142663 is a reply to message #142655] |
Wed, 07 September 2011 06:29 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| Mike Miller wrote on Tue, 06 September 2011 23:29 |
How about this:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=12520
Note: I labeled the picture back when I did not understand why things where the way they where. Ported Vacuum is plumbed the the x-mas tree (I think it is called a TVS?) along with manifold vacuum, then the output is sent to the vacuum advance of the distributor.
If I understand it correctly: The TVS(?) normally routes ported vacuum to the distributor to advance or not as needed. If the engine gets hot, into the "overheated" range, it will apply manifold vacuum to the distributor vacuum advance setting the timing to help the engine cool down.
So... the TVS(?) seems to be good thing to have.
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Mike,
Yes, TVS - Therrmal Vacuum Switch. And, you are completely correct in your understanding of its function.
If you already have it and it seems to work (not leak vacuum when cold), you might as well leave it there as it causes not loss in performance.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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