Emissions crap on a 74

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hemitheus

hemitheus

19? Plymouth Scampenstein
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Picked up a 74 scamp that is BONE STOCK. has everything and is pretty unmolested. Always had 72 and earlier cars.

I dont want to rip out the emissions equipment but am uncertain how any bolt in upgrades would be effected by them. Or are there parts of this system that can be safely removed and still pass inspection.

Anyone have experience with this system and its nuances with any advice?
 
You'd better check AZ laws, seems to me your state has some rather archaic emissions laws, IE you might NEED that "crap." (You sound like me, LOL)
 
I could be wrong but I think all the '74s had was the EGR system, some timing/choke controls (a timer and vacuum switch), and the evaporative control (the charcoal cannister). None of these will negatively affect performance if they are operational. Although usually the EGR is carboned up and not working, the evap system has had a line or two cut or the check valve is dead, and either the timer, or the vacuum switches, or both, are no longer functional...lol. I'd say check your local laws, and then look at what can be done. It would suck to change something and then when it goes to be registered be told to put it all back...
 
In the Phoenix and Tucson metro area, emissions laws apply to 67 or newer, which would require your EGR system be "in place on visual inspection". I've not lived there in eight years, but when I went it really depended on which smogmonkey got your car, none of them quite smart enough to follow an underhood emissions control diagram sticker, but many smart enough to see if an EGR valve has a hose hooked up to it (this seemed to be the main training point when I lived there). Everywhere else you can pretty much do whatever you want.
 
moper said:
.........................all the '74s had was the EGR system, some timing/choke controls (a timer and vacuum switch), and the evaporative control (the charcoal cannister). ...............................................................................................................None of these will negatively affect performance if they are operational. .
Click to expand...

So the reason that the 74's all coughed, gagged, overheated, and plowed down the road was just my misconception?
 
As vacuum lines and associated plumbing get old and leaky performance suffers. If everything is in good shape and working correctly, removing emissions control systems won't make the engine run better.

By 74 performance was definitely on the slide. Blame lowered compression and retarded ignition for most of the downgrade.
 
If you have to keep the Charcoal canister in place for your car to be legal, install a cheap fuel filter on the hose that connects to the carb.

I've personally seen the charcoal make its way to the carb, where it fills the carb up with crud (carbon pellets) and causes the vehicle to run like crap. A fuel filter inline allows vapors to travel, but not solids :glasses7:
 
A '74 will have coolant-controlled EGR, and it will have OSAC, Orifice Spark Advance Control, which delays vacuum to the distributor by 7 or 17 seconds each time the accelerator is pressed. Squeaked the cars past Federal emissions type approval tests so the cars could be offered for sale, kills driveability, performance, and economy. Find the OSAC valve on the side of the air cleaner housing. It's got one hose going to the distributor vacuum advance, and one hose going to the carburetor. Bypass this valve so one hose runs directly from carburetor to distributor.

Leave the canister in place and working; it only works for you, never against you, by trapping gasoline you bought so you can burn it instead of it floating off uselessly into the air.

If your '74 is in fact bone stock, it will have a seatbelt/starter interlock system; engine won't crank unless everyone in the front seat has his belt fastened. Even if you always wear your belt, you'll want to bypass this one-year-only system so a random failure doesn't leave you unable to start the car sometime. How-to has been posted several times; do a search on "interlock".
 
Y'welcome!

redbeard.gif
 
67Dart273 said:
So the reason that the 74's all coughed, gagged, overheated, and plowed down the road was just my misconception?
Click to expand...


No, I'd say those ones had problems. Were you tuning them? :D



Or did you expect all the cars sold ran that way off the dealer's lots?
I only had two 74s. The bone stock Duster ran like a top (and I sold it running that way). The other (E body) developed that seatbelt interlock issue Dan mentioned when I put my college books on the pass seat the first time. But it had no other emmisions equipment intact anyway.
 
In CA the '74 models and older don't have to smog check. I had to smog my 318 Satellite once. It failed the visual because when he revved it, the EGR linkage didn't move. I chased it for a couple days even replacing the vacuum amplifier with a couple borrowed from the boneyard. Finally tracked it to a small timer on the firewall that was meant to keep the EGR from operating within a certain period of starting the engine. I put a small tee in the vacuum line between that and the EGR to quietly bypass it. The EGR worked as advertised and it passed. I was told that timer was only installed for a portion of that one model year. Others here can likely confirm of refute that.

Definitely get rid of the seatbelt interlock. Mine was intermittent. After taking it out I opened the control box to see what was in there and a portion of the circuit board was burned. Simple to bypass in the wiring.
 
That particular timer might have been a short-production item -- timers like it were used on a whackload of Mopars from '74(ish) through to the last RWD passenger cars, the M-bodies, in 1989. There were a lot of different ones with different delay values and other operating parameters.
 
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