# 68 vacuum advance



## Matthew (Feb 11, 2011)

Are there any issues with running a single port vacuum advance as a replacement for the two port vacuum advance on the 68 with manual transmission? Thanks, Matt


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## BearGFR (Aug 25, 2008)

I wouldn't think so. The purpose of the dual port was for emissions. I'm not sure about the laws in VA but here a 68 car is emissions exempt now. For sure it won't hurt how it runs.

BEar


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## Matthew (Feb 11, 2011)

Bear, thanks. Sounds encouraging since it does not appear I can get a two port replacement in my limited search. Now, you say the two port was for emissions. You are taking me to school. I was under the uneducated impression it was for achieving maximum advance during deceleration with manual transimission. OK, sounds good. Thanks, Matt


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## geeteeohguy (Feb 2, 2008)

The dual vacuum was for advance AND retard. It was used to retard the timing on decel to help with emissions. Installing a single advance unit won't hurt a thing if your car is not currently in a smog check program.


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## Matthew (Feb 11, 2011)

Thank you sir. I must assume that is why finding a two port is challenging. Good to go. Matt


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## JVM225 (Jun 18, 2007)

That's good info. I have a working one on my car that I acquired back in the late 90's. It was almost impossible to find one back then, and I dread the day that something happens to it.
Stupid question: Does it matter which vacuum line you use if you only have the single port vacuum advance? 
The car is an automatic with the thermo vacuum switch on the intake. Both of the vacuum lines that go to the dual port vacuum advance come off of that switch.


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## Matthew (Feb 11, 2011)

JVM, I'm currently running off the TVC switch direct to the single port vacuum advance. Seems to be working fine, but I've been told by my kids (in their 30s) that I drive like my 80 year old mother. Since you have an automatic, both of your vacuum lines should be coming from the TVC. I hope this answers your question. Matt


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## JVM225 (Jun 18, 2007)

Matthew said:


> JVM, I'm currently running off the TVC switch direct to the single port vacuum advance. Seems to be working fine, but I've been told by my kids (in their 30s) that I drive like my 80 year old mother. Since you have an automatic, both of your vacuum lines should be coming from the TVC. I hope this answers your question. Matt


I'm thinking that if I have to go with a single port unit down the line I'll just plug the end that is supposed to go in the retard side and tuck it up under the distributer someplace.


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