Name that part ...
Thread Starter
8th Gear
Joined: Jun 2005
Posts: 8
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From: Acworth GA
Name that part ...
Hints:
1. It's off a 1973 L48, stock Qjet.
2. The vacuum lines at each end go to the carb and the one that goes out at a right angle goes to the vacuum advance on the distributor.
Obviously, I need a new one and I know it has something to do with the ported vacuum, I just don't know what it's called to ask for it.
Thanks in advance.
Daniel
1. It's off a 1973 L48, stock Qjet.
2. The vacuum lines at each end go to the carb and the one that goes out at a right angle goes to the vacuum advance on the distributor.
Obviously, I need a new one and I know it has something to do with the ported vacuum, I just don't know what it's called to ask for it.
Thanks in advance.
Daniel
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
I can't remember the name of it but you are better off without it. Unless you are going for NCRS it is not worth putting it back on. I have a brand new one in my "parts" box. I out it on then removed it. It was for emissions and most of them have been eliminated.
Pretty sure it is called a vacuum advance solenoid.
Pretty sure it is called a vacuum advance solenoid.
Melting Slicks
Joined: Nov 2003
Posts: 2,668
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From: St. Charles Mo
CI 5 & 8 Veteran
Originally Posted by Gordonm
Pretty sure it is called a vacuum advance solenoid.
Bullshark
Thread Starter
8th Gear
Joined: Jun 2005
Posts: 8
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From: Acworth GA
That's good to know. There's probably alot of emissions stuff that can be removed when I start looking, especially since I don't have to pass emissions here in Georgia. So can I just connect those three vacuum hoses with a T fitting?
Daniel
Daniel
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Drifting
Joined: Sep 1999
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Thats your Trans controlled spark,(TCS), soleniod. Like its been said, most people trash the system. Although, it doesn't adversely effect performance much.
It is connected to a full vacuum on your carb not ported. Your timing/ carb setup will need to be altered if you get rid of it.
You initial timing is set higher with the TCS ,due to no vac advance until 3rd gear on 4 speeds. Trashing the system and connecting vacuum directly to the distributor without altering your initial timing will more than likely give you too much total advance
It is connected to a full vacuum on your carb not ported. Your timing/ carb setup will need to be altered if you get rid of it.
You initial timing is set higher with the TCS ,due to no vac advance until 3rd gear on 4 speeds. Trashing the system and connecting vacuum directly to the distributor without altering your initial timing will more than likely give you too much total advance
Safety Car
Joined: Jun 2004
Posts: 4,652
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From: Lakeland Florida
I agree with Dennis.
You dont need to connect this back up, just go directly from the Vac Can to the carb/manifold for vacuum.
It was used to control the timing by altering the vacuum depending on gear selection.
kdf
Melting Slicks
Joined: Nov 2003
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From: St. Charles Mo
CI 5 & 8 Veteran
Originally Posted by dennis
Thats your Trans controlled spark,(TCS), soleniod. Like its been said, most people trash the system. Although, it doesn't adversely effect performance much.
It is connected to a full vacuum on your carb not ported. Your timing/ carb setup will need to be altered if you get rid of it.
You initial timing is set higher with the TCS ,due to no vac advance until 3rd gear on 4 speeds. Trashing the system and connecting vacuum directly to the distributor without altering your initial timing will more than likely give you too much total advance
It is connected to a full vacuum on your carb not ported. Your timing/ carb setup will need to be altered if you get rid of it.
You initial timing is set higher with the TCS ,due to no vac advance until 3rd gear on 4 speeds. Trashing the system and connecting vacuum directly to the distributor without altering your initial timing will more than likely give you too much total advance
except for the part about "doesn't adversely effect performance much" I guess it depends on your definition of much. Take for example the 70 LT-1, The vacuum advance contributes 0 to 12deg of advance between 7" and 12" of Hg. The 390hp 454 is 0 to 15deg between 8" and 15" of Hg. Hard for me to comprehend that much timing discontinuety setup between a 1st/2nd and 3rd/4th gear progression not affecting performance. How can you optimise for full throttle and not significantly affect mid range performance or visa versa? GM probably setup somewhere in the middle??
Bullshark
Drifting
Joined: Sep 1999
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Originally Posted by Bullshark
Dennis, except for the part about "doesn't adversely effect performance much" I guess it depends on your definition of much.
Take for example the 70 LT-1, The vacuum advance contributes 0 to 12deg of advance between 7" and 12" of Hg. The 390hp 454 is 0 to 15deg between 8" and 15" of Hg. Hard for me to comprehend that much timing discontinuety setup between a 1st/2nd and 3rd/4th gear progression not affecting performance. How can you optimise for full throttle and not significantly affect mid range performance or visa versa? GM probably setup somewhere in the middle??
Bullshark
except for the part about "doesn't adversely effect performance much" I guess it depends on your definition of much. Take for example the 70 LT-1, The vacuum advance contributes 0 to 12deg of advance between 7" and 12" of Hg. The 390hp 454 is 0 to 15deg between 8" and 15" of Hg. Hard for me to comprehend that much timing discontinuety setup between a 1st/2nd and 3rd/4th gear progression not affecting performance. How can you optimise for full throttle and not significantly affect mid range performance or visa versa? GM probably setup somewhere in the middle??
Bullshark
Little lost here. Vac advance contributes nothing in 1st and 2nd gear. You are right about the loss in between though.(If I read you right) Back in the 70's that made for a bit of a dog.
Today, my 70 L-46 can run a bit more advance,(initial),with the TCS working without pinging. Disconnected ,I can't bump it up much more ,(toatl timing),without pinging. Kind of a failsafe for me.
Also the cam makes it less of a noticeable loss on my L-46. Not a great performer down low.
Melting Slicks
Joined: Nov 2003
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From: St. Charles Mo
CI 5 & 8 Veteran
Sorry for not being more clear 
"Hard for me to comprehend that much timing discontinuety setup between a 1st/2nd (with no vac adv.) and 3rd/4th (with vac adv) gear progression not affecting performance." How can you optimise timing for full throttle and not significantly affect mid range performance or visa versa when in 1st/2nd? And then have a completly different situation in 3rd/4th. GM probably setup somewhere in the middle??
Bullshark
"Hard for me to comprehend that much timing discontinuety setup between a 1st/2nd (with no vac adv.) and 3rd/4th (with vac adv) gear progression not affecting performance." How can you optimise timing for full throttle and not significantly affect mid range performance or visa versa when in 1st/2nd? And then have a completly different situation in 3rd/4th. GM probably setup somewhere in the middle??
Bullshark
Last edited by Bullshark; Dec 10, 2005 at 08:23 PM.