Hello guys. I have a 1973 roadrunner 340 and was looking to clean up some of the ignition components. My first question regards that little vacuum advance module which is circled on the right in one of my pics. The top hose goes to the vacuum advance on the distributor and the bottom hose goes to the nipple for the vacuum advance on the carb. My first questions are what does this little module do and can it be removed and I just run a hose from the carb to the vacuum advance on the distributor? In the second pic I show where it is hooked up on the carb. Is that in the right spot for the vacuum advance? Now, in the first pic, there is a little band to the left of the vacuum advance module and it is connected to nothing. Can I get rid of that? Thanks in advance!!
Ignition Questions
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remytherat
Well-Known Member
The second pic is ported vacuum which is correct for the vacuum advance
67Dart273
Well-Known Member
The answers are in the 73 service manual, which you can download at MyMopar.com, for free
That manual and a few others got there because of some of the guys right here.
Before you modify stuff, you need to be aware of what state laws you have to meet for registration. IE do you have state "smog checks?"
That manual and a few others got there because of some of the guys right here.
Before you modify stuff, you need to be aware of what state laws you have to meet for registration. IE do you have state "smog checks?"
cudamark
Well-Known Member
That valve on the firewall is called an OSAC valve. It's used for reducing smog by limiting vacuum advance at certain times. If you don't need it for a smog test, yes, you can bypass it and run the vacuum hose direct from the ported vacuum source to the vacuum advance. I'm not seeing any "little band" next to the OSAC valve. The only thing out of the ordinary I see is a bent wire clip that looks to be holding the one vacuum hose on.
Thank you all for the replies. That “little band” that I’m referring to is the piece attached to the screw directly to the left of the osac valve. I had no idea what to call it but it’s almost like a strip of fabric that connects to nothing. Just wasn’t sure what that was. Thanks guys!!
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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If you want to clean stuff up, start with eliminating all those hose clamps and running hard lines. I mean the pressure line to the fuel bowl is just begging to make trouble.
As Mark wrote, its the OSAC valve. It's purpose is to delay vacuum based timing advance from responding when the throttle is opened. It's one of the few emissions reduction systems Chrysler used that is incredibley annoying. And Chrysler knew sporty drivers would notice. The Master Tech sessions for 1973 include one on 'drivability', along with explanations on how the various new emissions systems work.
Master Technician Service Conference - Chrysler's Training for Mechanics
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Yup.
Depending upon the state emission laws, a 50 year old car may not need any of the early pollution stuff.
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