| No "Christmas tree?" [message #255148] |
Sat, 12 July 2014 09:24  |
bhayes
Messages: 263
Registered: March 2010
Karma: 1
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Recently my 455's carburetor and I were having a staring contest (it won) while I was trying to figure out why the engine is not idling correctly, and noticed that my engine has no "Christmas tree," aka the thermostatic vacuum switch (TVS) found on page 377 of the manual. Is this required? Right now the distributor advance is connected directly to another vacuum port.
Bryan Hayes
'76 Eleganza II
Salt Lake City, Utah
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| Re: [GMCnet] No "Christmas tree?" [message #255150 is a reply to message #255148] |
Sat, 12 July 2014 10:05  |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Senior Member |
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Bryan,
Only in California when required by CARB! Other than that most have bypassed or removed the TVS and used the port for addition temp sensors.
JR Wright
78 Buskirk Stretch
75 Avion
Michigan
On Jul 12, 2014, at 10:24 AM, Bryan Hayes wrote:
> Recently my 455's carburetor and I were having a staring contest (it won) while I was trying to figure out why the engine is not idling correctly, and
> noticed that my engine has no "Christmas tree," aka the thermostatic vacuum switch (TVS) found on page 377 of the manual. Is this required? Right now
> the distributor advance is connected directly to another vacuum port.
> --
> Bryan Hayes
> '76 Eleganza II
> Salt Lake City, Utah
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: [GMCnet] No "Christmas tree?" [message #255160 is a reply to message #255150] |
Sat, 12 July 2014 12:07 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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Senior Member |
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Mine has been gone for years. The vacuum advance hose should be connected directly to the highest port on the front of the carb.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] No "Christmas tree?" [message #255162 is a reply to message #255160] |
Sat, 12 July 2014 12:44 |
Otterwan
Messages: 946
Registered: July 2013
Location: Lynnwood (north of Seattl...
Karma: 0
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Senior Member |
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Mine too. Took it out and installed a direct reading temperature gauge. One of the best, cheapest, easiest upgrades you can do. Because personally I like reading 200° rather than "halfway between the the 2nd and 3rd hash marks" ;O)
1977 Birchaven, Lynnwood WA - "We may not be able to stop all evil in the world, but I know that how we treat one another is entirely up to us."
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| Re: No "Christmas tree?" [message #255173 is a reply to message #255148] |
Sat, 12 July 2014 13:55 |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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bhayes wrote on Sat, 12 July 2014 08:24Recently my 455's carburetor and I were having a staring contest (it won) while I was trying to figure out why the engine is not idling correctly, and noticed that my engine has no "Christmas tree," aka the thermostatic vacuum switch (TVS) found on page 377 of the manual. Is this required? Right now the distributor advance is connected directly to another vacuum port.
The only purpose of the christmas tree is to switch distributor vacuum from ported to manifold vacuum when the engine gets hot. That allows the engine to run more efficiently and at a higher idle in order to help cool it.
Bob de Kruyff
78 Eleganza
Chandler, AZ
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