To De-Smog or not to De-Smog...

[74DartCustom]

I have a '74 Dart Custom /6. It is a California car, and the intent is to make it a daily driver. It is no longer restricted by any emissions testing, and the engine compartment is a cluttered mess.

Perhaps my searching skills are not up to par, but has anybody gone through how to properly "de-smog" a /6? I'm sure that much of the junk in the engine compartment is superfluous or even capable of robbing small amounts of power. What modifications may be made to simplify the view under the hood? I do have A/C, which I will be keeping, but holy crud- there are like, four vacuum lines just going to the air cleaner!

 

[63valiant]

Done correctly you can pull most of that stuff. Just don't start jerking stuff though, the car will more than likely have to be re-tuned to compensate for the changes.
Optimum end result would be hose for the PCV, line for the vacuum advance, and whatever your heater and AC requires.

Don't throw the smog stuff out though, all to often there is some bureaucrat that tries to reintroduce the Pre '76 cars back into the smog program. So far we've defeated them, but you can never tell what may happen.

 

[74DartCustom]

HA! Ask my wife, I never throw anything out!

So, perhaps this is the wrong place to ask- but what the crap are all those sensors and vacuum hoses doing on my air cleaner housing? I've located the charcoal canister. I assume it can be eliminated. I put a Edelbrock breather on the valve cover and eliminated that hose going to the air cleaner. To soon to tell if the engine likes it or not. The carb will be getting some adjustment asap anyway- the previous owner set it by ear after getting the vacuum lines mixed up. I'd like to eliminate any extraneous junk prior to adjusting it in order to save myself some time and trouble.

The vacuum amplifier is already in the trunk, and it looks like there are a few newish vacuum caps on the electric choke assembly. I get the feeling that if I "unfix" a lot of what has been done, that the car will be a bit happier.

 

[74DartCustom]

Double strike on the keyboard. Sorry. Disregard.

 

[63valiant]

You'll probably want to keep the charcoal canister. In the early days the fuel tanks were vented into the atmosphere. In later years they ended up installing the charcoal canister and routing the ventilation through it. If you remove the canister and cap off the line you'll no longer have a vent which will cause problems immediately. If you remove the canister and leave the vent open you'll be smelling fumes. One option might be to cap off the line and use a vented gas cap, but I do not know if those are available anymore.

You might want to search around/ask your other questions at slantsix.org there's a lot of good information over there.

 

[fjr]

Many emission control components have minimal or no effect on fuel economy and power. You should understand what they do before you yank it off. Also, even here in Ontario, all emission controls must remain in place even even if they are e-test exempt. There have been cases where hot rodders have been fined by the police for failing a vision inspection.

 

[slantsixdan]

Don't just randomly start yanking stuff out of the engine bay. See here. The single biggest improvement you can make is also one of the easiest: bypass the OSAC valve. Presently there's a hose running from the carburetor's spark advance port to the OSAC valve on the side of the air cleaner housing, and from there to the distributor. Instead, run a hose directly from the carburetor spark advance port to the distributor.

 

[63valiant]

I have to disagree, smog equipment and specs are notorious power and fuel economy robbers. The slant is just one example of the before and after of the smog regulation. The early 60's slants were quite strong stock, the late 70's slants barely got out of their own way.
When we buy parts for Ford FE engines, in example, we buy timing sets for the early engines as they aren't retarded like the smoggie ones are. Get the proper timing and you gain both fuel economy & power.
And just as a general rule we see 1 to 2mpg gain in just pulling the smog pump belt in any engine, it takes power to turn any component and that means fuel lost too.
I agree with Dan it's best to not just randomly pull stuff off. If you know what each component is doing you'll know how the engine is tuned to it and what other systems may be tied into it. But you absolutely can get rid of unnecessary problem ridden junk.

 

[74DartCustom]

I've never been one to randomly pull stuff, but extraneous part removal is usually my favorite part of any project.

I removed the OSAC (actually right before reading your post), and then noted that the vacuum line going to my dizzy was pretty lose and melted. New hose going directly to the carb and the whole engine seems happier. It eliminated a high idle (undoubtedly a lean condition caused by the leak) and a slight miss that I'd had going.

FJR- It is rare that I can be happy about California's smog laws. Thanks for that! ;)

63Valient- Talk to me about this smog pump. Belt-driven, you say? What is it for? How do I properly bypass it?

Do you see any reason to keep the carburetor attached to the charcoal canister?

Thanks for all your help. I think I'm going to like it here.

 

[slantsixdan]

I removed the OSAC (actually right before reading your post), and then noted that the vacuum line going to my dizzy was pretty lose and melted.

Sounds like a good time to go through and check everything under the hood. Tune-up parts and technique suggestions in this thread. Carburetor operation and repair manuals and links to training movies and carb repair/modification threads are posted here for free download.

New hose going directly to the carb and the whole engine seems happier.

Yep!

Talk to me about this smog pump. Belt-driven, you say? What is it for? How do I properly bypass it?

It might or might not be present on your car. Look at the front of the engine. If you have about a 7" round aluminum-housed device driven by a belt that is not an A/C compressor, not a power steering pump, not a water pump and not an alternator, you've got a "smog" (air) pump. It takes almost zero power to spin and there's very little to be gained by eliminating it (except some underhood space). To do so, unbolt it, then remove it and its tubing which connects to the cylinder head at the far rear. Buy from a Mopar dealer a blockoff plate 3751 249 with gasket 4275 834.

Do you see any reason to keep the carburetor attached to the charcoal canister?

Absolutely yes! It does nothing but save you gas money and make your garage less stinky. Go read the link I provided above.

 

[2 Darts]

The PO had already done away with the OSAC and related lines. I took out the EGR valve and plugged the intake manifold. I replaced the exhaust manifold with one that did not have an EGR hook up. Capped the related EGR vacuum ports. Runs better and gets a little better fuel mileage.

 

[slantsixdan]

There are no exhaust manifolds with EGR hookups -- it's the intakes that have (or don't have) the mounting pad for the EGR valve.

 

[2 Darts]

There are no exhaust manifolds with EGR hookups -- it's the intakes that have (or don't have) the mounting pad for the EGR valve.

True. I'm still working on my English. It would have been more correct for me to say that I replaced my EGR compatible exhaust manifold with one that was not provisioned to interface with the EGR valve.

 

[slantsixdan]

True. I'm still working on my English. It would have been more correct for me to say that I replaced my EGR compatible exhaust manifold with one that was not provisioned to interface with the EGR valve.

No, still incorrect. There is no such thing as an "EGR compatible" slant-6 exhaust manifold. The differences in various slant-6 exhaust manifolds have absolutely nothing to do with presence/absence of EGR. There is no such thing as a slant-6 exhaust manifold with provisions to interface with an EGR valve; there are intake manifolds with/without this provision.

 

[340mopar]

I have never found a "good" smog pump to take way 1 - 2mpg. It takes very little power to spin a smog pump, 1/8 - 1/4hp at very worst. Heck, I only loose only .5 - 1mpg with my A/C on.

74DartCustom, the smog pump is just a little vane air pump. It injects air into the exhaust system so the heat of the catalytic convertor has oxygen to burn the incomplete burned fuel. They aren't very pretty but not much of a power robber.

I would add that although your state may not require you to pass emission tests, emission equipment is a Federal thing and techically is still required to meet Federal emission laws of the year it was manufactured. With that being said there is a ton of us without our "mandated' equipment. I am one of them on my '65 Valiant (no PCV valve, I use header EVACs)


Chuck

 

[caferacerx]

No, still incorrect. There is no such thing as an "EGR compatible" slant-6 exhaust manifold. The differences in various slant-6 exhaust manifolds have absolutely nothing to do with presence/absence of EGR. There is no such thing as a slant-6 exhaust manifold with provisions to interface with an EGR valve; there are intake manifolds with/without this provision.

E.G.R. stands for exhaust gas recirculation valve it is used to reduce the formation of NOx by introducing a small amount of exhaust into the combustion chamber it is connected to both the intake and exhaust

 

[slantsixdan]

I have never found a "good" smog pump to take way 1 - 2mpg. It takes very little power to spin a smog pump, 1/8 - 1/4hp at very worst.

Correct -- at very worst. If the air ("smog") pump is eating anything even close to 1hp, it's soon to grind itself into a puddle of slag.

74DartCustom, the smog pump is just a little vane air pump. It injects air into the exhaust system so the heat of the catalytic convertor has oxygen to burn the incomplete burned fuel. They aren't very pretty but not much of a power robber.

Only thing wrong with this info is that the car in question is a '74 -- no catalytic converter. The system, called secondary air injection, was introduced almost a decade before the catalytic converter.

 

[slantsixdan]

E.G.R. stands for exhaust gas recirculation valve it is used to reduce the formation of NOx by introducing a small amount of exhaust into the combustion chamber

Correct.

it is connected to both the intake and exhaust

Dude, don't guess at things you don't know. Go use your eyes. Go look at two dozen different slant-6 exhaust manifolds. There is no connection for an EGR valve on any slant-6 exhaust manifold. Right from the very start in 1960, the slant-6 intake and exhaust manifolds bolt together at the center to provide intake manifold heating (the hot spot) for proper vaporization of fuel: exhaust passes across the underside of the intake manifold floor, and that's how the intake is heated. When valve-controlled EGR was introduced in '73, an EGR mounting pad and two new passages were added to the intake manifold. One passage goes from the underside of the intake manifold floor to the EGR valve mounting pad. The other passage goes from the EGR valve mounting pad to the inside of the intake manifold. The EGR valve, mounted on the intake manifold, controls the flow of exhaust from the underside to the inside of the intake manifold. The exhaust manifold does not know or care whether an EGR-equipped intake manifold is bolted on. Deleting EGR from a slant-6 does not involve any mods to the exhaust manifold because (everybody, all together now!) there is no such thing as a slant-6 exhaust manifold with EGR provisions.

(the '72 California slant-6s had a very primitive EGR "system" consisting of nothing but a hole in the intake floor, connecting the underside to the inside so exhaust entered the intake tract whenever the engine was running. Engines so equipped were a bitсh to start, idled high and poorly, and got awful gas mileage.)

 

[fjr]

I have to disagree, smog equipment and specs are notorious power and fuel economy robbers. The slant is just one example of the before and after of the smog regulation. The early 60's slants were quite strong stock, the late 70's slants barely got out of their own way.

There is a bit more to the apparent loss in power than than just added emission controls. In the 60's, gross power was measured at the flywheel while, in the 1970's, net power was measured at the rear wheels. Also, larger tires (14" from 13") and lower ratio axles (like 2.76:1 from 2.93:1) were used to improve fuel economy, which had a detrimental effect on acceleration.

There are ways to improve fuel economy and power without removing the emission controls. You would probably notice a bigger improvement in both with a rework of the advance curve than by yanking off the smog equipment. I've also used the EGR in my 73 Dart to run higher amounts of advance for better fuel economy as carbon was causing knock with 87 octane.

 

[slantsixdan]

There is a bit more to the apparent loss in power than than just added emission controls.

True and correct.

In the 60's, gross power was measured at the flywheel while, in the 1970's, net power was measured at the rear wheels.

No, both SAE Gross and SAE Net horsepower are measured at the flywheel. The difference is that Net horsepower is measured with the engine configured and equipped more in line with an actual vehicle installation. Read more about it here.

Also, larger tires (14" from 13") and lower ratio axles (like 2.76:1 from 2.93:1) were used

Yes, and the cars grew heavier over the years. Bigger front bumpers and side impact beams in '73, bigger rear bumpers in '74, reinforced windshield headers in '75, etc.

 

[SpeedThrills]

If I remember correctly, smog engines were jetted leaner, which made them run hotter. This was compensated for, partially by the air injection pump, which helped keep things cool.
I'd remove all the smoggy stuff, and use a carb and distributor from a pre-smog motor. This is easy for me to say, though, cuz I'm not familiar enough with the actual what-will-work part.
"Proceed at your own risk." :read2:

 

[fjr]

Thanks for the correction, Dan. Rear wheel hp is definitely not SAE net hp. I don't know what made me think they were the same.

 

[roccodart440]

To the original poster. Smog equipment is counterproductive and cluters things up. get rid of it.

 

[2 Darts]

Since I started this crap about EGR, I need to say that I stand corrected. Exhaust gas has always been present at the base of the intake manifold for the purpose of heating the fuel air mixture. Installing an EGR provision on the intake under the carburetor taps this source of exhaust gas for the emission reduction purpose. Photo from parts manual included.

At the same time, I know what I did. To defeat EGR, I hogged out the hole under the carburetor in the intake and pounded an oil gallery plug into it. I then replaced the exhaust manifold with one that can not provide an exhaust gas source for EGR, nor for carb heat. I also made sure the vacuum source to the EGR valve I had disabled was plugged. Due to the removal of the exhaust manifold, I had to fabricate stand-offs in order to retain the factory throttle & kickdown linkage. Photos attached.

You OK with this, Dan?

 

[slantsixdan]

If I remember correctly, smog engines were jetted leaner, which made them run hotter. This was compensated for, partially by the air injection pump, which helped keep things cool.

No, it's the opposite. Air injection makes the engine run hotter, not cooler. It's because unburned fuel meets injected air, catches fire and burns in the exhaust ports of the cylinder head. This puts a good deal more heat into the metal.

I'd remove all the smoggy stuff, and use a carb and distributor from a pre-smog motor. This is easy for me to say, though, cuz I'm not familiar enough with the actual what-will-work part.

Yeah, guessing isn't a good way forward. In the first place, using a distributor from a "pre-smog" engine would mean giving up electronic ignition and going back to breaker points -- yuck! In the second place, several of the best slant-6 distributors (in terms of advance curves out of the box from the factory) are from '76-'77, right in the middle of the smog era.