Vacuum hose routing on temperature operated by-pass valve (Radiator)

[dhel]

Hi guys, having my Dart now for a couple of years imported from Switzerland, I was wondering all the time what the small black box with the note "CARB" on it was sitting on the right side of firewall with 2 open plugs. I took a picture of it, so everyone exactly knows about what part we are talking here...

View attachment WP_20150703_001.jpg

Now, since my fan is causing trouble, I looked up info on the fluid fan drive in the manual, and I notice a hose routing diagram... mentioning the complete wiring from manifold vac and ported vacuum over that box and the by-pass valve back to the vacuum pot on the distributor.

View attachment Vacuum routing.jpg View attachment By-pass valve.jpg

Nice, only one issue here: the manual shows a 3 port by-pass valve on the radiator. I only have a 2 port. And there is no marking on it at all.

View attachment WP_20150703_002.jpg

Some of you can help me here?
Anybody knows what the "black box" in between is doing exactly? That the by-pass valve increases idle rpm as from certain high temperatures while opening manifold vacuum is clear to me. Given your distributor is hooked up to the ported vacuum...

Thanks for info!

 

[67Dart273]

We need to know what year model and engine combo you have to start

Cars built "for export" may very well be different than the States. It's "bad enough" some years had special requirements just for the State of California.

 

[Bad Sport]

We need to know what year model and engine combo you have to start

That would be helpful.

I had all that on my car, and I just removed it all. The piece in the radiator, I pulled out and put a brass plug in the hole.

 

[dhel]

He guys,

My Dart is a '73 with a 318

Daniel

 

[67Dart273]

After taking a quick look in the 73 shop manual, you problem may be simple. It appears you simply have the incorrect thermostatic valve in the radiator. Look "around" page 25-8, "OSAC" which amounts to spark control. It explains things fairly well. "Good luck" getting the correct valve. I've no idea

The 73 manual (two parts) can be downloaded over at "MyMopar." It actually CAME from this site!!!

http://www.mymopar.com/index.php?pid=109

 

[Logan]

I think you'll find "CARB" means "California Air Resources Board". CA legislated their own smog rules back then and it was common to see this on smog related parts. The car was probably originally sold in California.

 

[AJ/FormS]

I would totally bypass that system, and rework the dizzy to put everything back to a pre-OSAC state.
That OSAC valve IIRC has a temp sensor in the cowl. It only passes the ported spark vacuum signal through itself under certain temps. But it doesnt send the vacuum to the dizzy, it sends it to the engine temp Thermosensor. The thermosensor sends this ported signal, or manifold vacuum, or nothing, to the dizzy, depending on the engine temp. It was a very early attempt at keeping NOx down.IIRC vacuum was only allowed during the cold start cycle and during overheats. Or some such bs.
Can you imagine; burn 50% more fuel, to reduce NOx by 50 %.Or some such nonsense. Some engineering! Can you tell I'm not impressed?
IMHO its a BS system. Bypass it and watch your MPGs go up, and driveability too.NOx be darned

 

[67Dart273]

I would totally bypass that system, and rework the dizzy to put everything back to a pre-OSAC state.
That OSAC valve IIRC has a temp sensor in the cowl. It only passes the ported spark vacuum signal through itself under certain temps. But it doesnt send the vacuum to the dizzy, it sends it to the engine temp Thermosensor. The thermosensor sends this ported signal, or manifold vacuum to the dizzy, depending on the engine temp. It was a very early attempt at keeping NOx down.IIRC vacuum was only allowed during the cold start cycle and during overheats. Or some such bs.
IMHO its a BS system. Bypass it and watch your MPGs go up, and driveability too.

I would agree, but don't know if he has to "pass smog" in his country, Belgium?

 

[TylerW]

Ugh, this got confused, just like most of the smog hose threads but thanks for helping guys. I have two '73's, both a slant and a 318, so let me take a crack at it.

The first thing I noticed is that the vacuum hose routing picture above is for a big-block, which a '73 Dart never had. So, disregard whatever you see in that picture.

Second, the 2-port thermo valve on the radiator controls the EGR valve. One side gets fed ported vacuum from the carb, the other connects to the EGR valve. The valve is there to prevent the EGR from operating below a certain engine temp. Slant six cars don't have the valve in the radiator. The EGR is controlled another way.

Note that these things changed year-to-year. Later slants got temp switches in the radiator and/or the cylinder head.

Next up is the OSAC valve. Orifice Spark Advance Control. In very basic terms it is a delay valve inline between the carburetor advance signal and the distributor vacuum advance. It's a smog thing. People say to remove them, but on the low-compression stock engines in the cars I've had I've never noticed a difference.The '73 Valiant has all of it and it runs fine.

There is NO temperature switch control of the OSAC. One line connects to the carburetor, the other to the vacuum can. That's it. CARB means carburetor, DIST means distributor.

The Slant six car uses the vacuum "relief" mounted on the firewall next to the OSAC, the 318 car does not. It is blanked off with a plate. That's because the Slant car has the "hockey puck" vacuum transducer, the 318 does not.

Hope this helps.

 

[67Dart273]

Ugh, this got confused, just like most of the smog hose threads but thanks for helping guys. I have two '73's, both a slant and a 318, so let me take a crack at it.

The first thing I noticed is that the vacuum hose routing picture above is for a big-block, which a '73 Dart never had. So, disregard whatever you see in that picture.

Second, the 2-port thermo valve on the radiator controls the EGR valve. One side gets fed ported vacuum from the carb, the other connects to the EGR valve. The valve is there to prevent the EGR from operating below a certain engine temp. Slant six cars don't have the valve in the radiator. The EGR is controlled another way
Hope this helps.

OK I DID refer him to the 73 manual, which does list the other engine combos Seems to me the slant 6 info just confuses the issue

There is NO temperature switch control of the OSAC. One line connects to the carburetor, the other to the vacuum can. That's it. CARB means carburetor, DIST means distributor.

.

Yup. You are correct

 

[dhel]

The 73 manual (two parts) can be downloaded over at "MyMopar." It actually CAME from this site!!!

http://www.mymopar.com/index.php?pid=109

Indeed, the pics were taken from the '73 manual.

After taking a quick look in the 73 shop manual, you problem may be simple. It appears you simply have the incorrect thermostatic valve in the radiator. Look "around" page 25-8, "OSAC" which amounts to spark control. It explains things fairly well.

I would agree, but don't know if he has to "pass smog" in his country, Belgium?

Well, as I said, this car coming from Switzerland. That is why I wonder so much that I have the incorrect thermostatic valve in the radiator!!! And the OSAC not connected… Why? Since Switzerland is comparable to California in some way, even “oldtimer” cars have to pass “gas exhaust tests”. This probably also explains why the car has been equipped with the California stuff! Not only for new cars Switzerland has high environmental requirements, but you simply cannot get an “oldtimer” status as well for your car just by its age… It has to be fully maintained, preserved and in a proper technical condition. This car had that status, and I have all of the Swiss paperwork, including the exhaust test results. So why did they remove the hoses / disconnect the OSAC? Didn’t it bring that much? Apparently not. The car passed the tests brilliantly. But anyway, the setup must have been changed.

I would agree, but don't know if he has to "pass smog" in his country, Belgium?

Well, that being a requirement in Switzerland, Belgium has a very simple rule when it comes to “oldtimer” cars: none! You pass a check-up when registering as an “oldtimer” once: it just comprises an optical inspection of body, frame and lighting, no brake test, no light beam test, no shock absorber test, no suspension test. They just check paperwork and the presence of the chassis number STAMPED in the car. A problem with US cars, that only come with the tag on the dashboard. That was no issue in Switzerland (!!!), but the Belgians wanted the chassis number STAMPED and confirmed by Fiat Group.

So no, no regulations regarding “smog” at all.

Ugh, this got confused, just like most of the smog hose threads but thanks for helping guys. I have two '73's, both a slant and a 318, so let me take a crack at it.
The first thing I noticed is that the vacuum hose routing picture above is for a big-block, which a '73 Dart never had. So, disregard whatever you see in that picture.

Right Tyler, I was already expecting that. That’s sometimes the confusion with multiple cars / engine types being described in same manual…
And that’s the point where other enthusiasts can help out! Thanks to all on this forum!

Second, the 2-port thermo valve on the radiator controls the EGR valve. One side gets fed ported vacuum from the carb, the other connects to the EGR valve. The valve is there to prevent the EGR from operating below a certain engine temp. Slant six cars don't have the valve in the radiator. The EGR is controlled another way.

And that’s the point where I’m gonna need your help guys, because the way the hoses are being routed now may be not correct. Simply because only one connection of the thermo valve is not being hooked up, which seems very unlogical to me. Or not?
I’ll attach pictures of the routing right now, better than describing it.
If like Tyler says, one side gets fed ported vacuum from the carb, the other connects to the EGR valve, then below setup already seems incorrect…

View attachment IMGP0374.jpg View attachment IMGP0375.jpg

But on the other hand, if I look into page 25-14 of the manual, I notice almost this same setup... except for the black with green (seems more blue to me...) stripe hose is going towards the temp control valve? Not to the radiator thermo valve......

View attachment EGR Hose routing.jpg

So if anyone can help me out with this?