AMC V8 Emissions control systems

Right, anyone got any idea if all the emissions stuff (EGR valve etc) is actually required or can I bypass this system, If I can what do I block off or blank, any help appreciated

Heres a pic of what I have at present

 

You can disconnect the EGR system, but the engine will run better if it's functioning.

My recommendation is to put everything back to how it was from the factory. Should be straightforward if you have the factory manual.

 

Wouldn't it be starving the engine of power (like most emission control systems), why would the engine run better with it? Is is a carb setup issue?

 

not emissions related, but it is a bad habit to let anything lie on top of the choke plate/butterfly on top of the carb for obvious reasons.
Emissions related: if you have the pump and brackets and air manifolds, I'd run it.
If most is missing/broken, it would be costly to replace and bring the AIR system back up to snuff....my 0.2 worth.

 

Its purpose is to lower combustion chamber temperatures to reduce the production of nitrous oxides. This is accomplished by diluting the charge with what's essentially an inert gas: the exhaust gas. If you remove the diluting exhaust gas, you make the air-fuel ratio leaner. Typically the engine will run ok without it, but the engine certainly won't run any better without it, if you do nothing else. I don't have any hard evidence that the engine will run better, but anecdotal evidence says that power and drivability is better with the EGR connected.

IMO most of the hatred targeted at the external emissions devices comes from owner's frustration with the complexity and appearance of the engine, not any real technical advantage to removing the devices on their own. Certainly if you remove all the devices and go to a non-emissions carburetor and camshaft, the engine will have more power, but... that's not a very scientific test. Most of the devices, such as vapor recovery, air injection (a negligible parasitic load), catalytic convertors, and more, have zero effect on performance. Owners hate them because they resent having to maintain them, and they are ugly and puzzling. Removing them for performance reasons is mostly a rationale without a logical basis, IMO.

 

I'm putting my EGR and vapor canister back on...doesn't seem like too much trouble, and of course the PCV. But I'm not putting on any other emissions related components. I am using the factory service manual to put it together. You can find it online also.

 

I have what you see in the picture, there was also a plate beside the EGR valve but I took this off to clean up the engine, looked like it only supported the throttle spring? I don't have the factory headders? and will be running Hedman Headers instead.

 

The EGR on the California equipped vehicles was activated only in high gear. On the T-15 in particular there is a switch that is activated when you shift into 3rd gear. It completes the ground for an electronic vacuum booster that activates the EGR valve. Other transmissions may not have this activation switch, the T-18 I swapped in doesn't have it for instance. This particular part of the emissions system was so troublesome that I disconnected the EGR once the laws changed here and the 1974 models became smog exempt. The engine runs well and more consistent without the malfunctioning vacuum booster. I removed the rest of the system after I did a top end rebuild and just didn't put the smog equipment back on. My 2 cents is that if it's not already there don't bother installing it unless your local laws require it.

 

Mine has run great for years with all that stuff gone. You might just need to adjust the carb.

 

This is not correct. The '74 EGR system does have an extra component, the back-pressure sensor, but it is not controlled by the transmission. There exists transmission controlled spark (TCS) which is present on 49-states 304 CJs, but not in CA. This retards the spark advance in top gear, and does not affect the EGR.

I had to refer to the manual to check these facts - I can keep most of this stuff in my head, usually, but not everything always. The '74 manual is online - here's the emissions chapter: http://oljeep.com/gw/74_tsm/4A-EmissionControl.pdf The systems and applications change from year to year, and the factory manual is your best reference.

 

I agree these parts are not discussed in the factory service manual, I have one and there is no mention of it. Maybe my jeep is an anomaly, or there was a limited run of this particular type of system due to the availability of this particular EGR valve, or the CA smog requirements are not discussed in the factory service manual, but I failed smog tests several times for this system not operating in the manner I described above. I traced the wires from the vacuum switch to the transmission switch that is activated in 3rd gear of the t-15. When in third gear the vacuum was activated by the switch and the EGR opened. When bypassing this switch and running constant vacuum to the EGR the engine would choke on its own exhaust gasses, as the vacuum was strong enough at idle to open the EGR. I fought with, examined and diagnosed this system repeatedly during the years a smog check was required. I even went so far as removing the system and presenting the factory service manual to the smog technician who agreed that while there was no mention of it in the manual, it was required as he was able to produce the smog requirements for CA in the 1974 model year that stated this type of system was required for my vehicle.

 

What are local laws and the intended use. Mine is 98% off road and we are not regulated here so no smog test to pass. My jeep has virtually everything emissions related removed and runs fine. I do have a PCV valve but thats it. If you do remove anything keep it. If I were to need to pass emissions or wanted to do a correct restoration it would cost a bunch to find and replace all the componets.