Okay so somebody suggested I bypass the OSAC valve to improve mileage and driveability... I have some questions.

What is it? What's it supposed to do? What is affected by taking it out and how do I do it?


Any help would be great.

_________________
1973 Dart Swinger Super 6 with 71k
1976 Datsun 280ZX with Mopar I-6

O rifice
S park
A davnce
C ontrol

Valve.

The OSAC valve is a device which delays the advance of the ignition timing. When acuum is applied from the port on the carb the valve delays sending the vacuum signal to the distributr. Bypassing the valve will simply make your vacuum advance work immediately instead of delayed.

To bypass the valve all you do is take the hose that goes from the carb to the OSAC valve, disconnect it from the OSAC valve, and connect it to the vacuum advance pod on the distributor.

A primitive emission control device which delays vacuum to the distributor vacuum advance pod by 7 to 17 seconds (depending on the exact valve in your car). It was designed with one purpose in mind: To get the car configuration past the ludicrously unrealistic Federal Emission Compliance Certification tests so that cars like it could be sold to consumers. Removing it allows the vacuum advance to work normally, which greatly improves driveability and mileage with zero negative side effects, and even if you have to pass an emission test of some description, you'll still pass just fine without the OSAC valve.

On your '73, the valve is located on the firewall, near the passenger side. ('74-up valves were on the air cleaner body). It has a hose running to the carburetor, and one to the distributor. What you want to do is run a correctly-sized hose directly from the carburetor to the distributor, bypassing the OSAC valve. That's it!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Sounds easy enough


Thanks

_________________
1973 Dart Swinger Super 6 with 71k
1976 Datsun 280ZX with Mopar I-6

I took a look under my hood and somebody already bypassed the valve, but here's the thing.... There is no vacuum line going to my distributor at all. There are four lines running out from my vacuum booster.

1) To the intake
2) To the carb
3) To the EGR
4) To another control valve on the firewall right next to the OSAC (not sure what it is)

There is no vacuum line from the distributor to the carb, or any vacuum to the distributor at all for that matter, I can't even really see where the line would go, but it's in a tight spot so maybe I can't see it.

Is there supposed to be a line from the carb to the dist?

_________________
1973 Dart Swinger Super 6 with 71k
1976 Datsun 280ZX with Mopar I-6

Errrr...from your vacuum booster? The only thing called that, under the hood of your car, is the power brake booster located immediately behind the brake master cylinder. If you really have lines running from the brake booster to the carb, EGR and some random firewall valve, then somebody has badly foozled the vacuum hose routing on your car. Have you got the factory service manual yet?
Definitely yes!

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

You must mean the EGR vacuum amplifier.

Ther emost definitely should be a vacuum line running from the nipple on the distributor vacuum advance pod up to the passenger side of the carburetor.

I am assuming from your handle that you have a 73 swinger, and I am alsop assuming that it is stock so it most likely has a Holley 1920. The post for the distributor on the carb should be on the bottom of the carb on the passenger side, close to the large PCV port.

Amplifier... booster... sorry, mixed my vocabulary up.... But anyway, yes, I have four hoses running out from *that thing* up on top and no hose from my carb to dist. So I'll have to correct that and get back to you guys.

Who knows what happened there. I've owned the car for about 6 months and didn't really notice it. Previous owner might've done it, do you think that could be why I have a rough idle and such bad gas mileage? It seems like I'm one of the only people who regularly gets V8 miles out his /6.

_________________
1973 Dart Swinger Super 6 with 71k
1976 Datsun 280ZX with Mopar I-6

Do you have the Factory(!) Service Manual for your car yet?

_________________
一期一会
Too many people who were born on third base actually believe they've hit a triple.

Don;t feel bad. i have an 86 Dodge van with a slant six. It has a 32 gallon gas tank. My last tank of gas took me 140 miles. 32 into 140 = 4.4 miles per gallon! Yay! Now you see why I am trying to get my lean burn computer back working again....