I have a '73 coupe and currently have the EGR valve on my car but the port on the carb and EGR are capped off. I was wondering if anyone is actually running an EGR and if so how it works? I heard they do not function well and cause more issues than its worth having them hooked up since they were such an early design. Thoughts?

 

My 73 is the same way, been that way since I've owned it . I don't know if the p.o. had a problem with the valve or the operation of the system in general. Car runs ok except the idle drops excessively when put in gear. That is the next problem to chase on my list.

 

I have a TH400 auto as well and the idle is ~1,400 RPM in park and will drop down to ~800-900 in Drive. I have the idle set a little higher than normal just due to the cam I have in it.

 

EGR is connected on my 73 and I haven't had any problems with
the engine running on mine. Haven't checked the RPM in PARK, but
it idles at @800 in drive with foot on brake when warm.
Also TH400 transmission. Photo below of EGR connected.




Donnie

 

Thanks for the photo!

 

Egr works fine when it works...like just abouf everything else. Rather primitive way to control it. Port vacuum and temp controlled vac switch. When valve is stuck open or partway open won't isle worth a damn. Equiv of big vac leak. So unhooking a bad valve is sometimes no help.

 

EGR stands for Exhaust Gas Recirculation. The valve is supposed to be plumbed into ported vacuum, opening under part to wide open throttle, introducing exhaust into the intake charge to cool it down and thus reduce NOx emissions.

they work at what they are intended to do, but they leak and get stuck due to carbon and gunk from the exhaust over the years. when they do not seal fully, idle quality is compromised. when they stick and don't close fast enough, you can stall when letting off throttle or at a stop light.

you can make your own determination about whether they are "worth" it or not. a simple vacuum operated EGR like on the early motors has a lot more failure modes than more modern valves that combine backpressure, temp sensors, etc. to make them more robust. either way, you need to decide if lowering the temp in the combustion chamber has benefits, and how to properly tune the engine if you use one or not. many of us not in an emission testing state prefer to fill the combustion chamber as full as possible with combustible gas, rather than inert exhaust. YMMV...

 

I posted this in another thread about EGR's:

I just went through this EGR issue with my 100% stock 1994 Mustang GT 5.0 (31,000 miles) except BBK shorty Headers, Magnaflow high flow cats (4) X pipe and Magnaflow cat back mufflers-2.5 inch system and K&N cold air package. The Ford system is different than the 78 EGR with an electronic sensor detecting EGR movement linked to the check engine light, EGR vacuum operation under all engine conditions except idle-High vacuum closed, lower vacuum EGR valve open. The issue was that when the engine was hot, it would ping and rattle the valves under moderate throttle to WOT and mid to high RPM operation. I made sure the timing was factory correct, plugs were good, and wires were new...no change. Changed to 89 octane gas which helped but did not eliminate the pinging. Tried to keep it 100% factory correct but to no avail so tried disconnecting the electronic nanny-check engine light, removing vaccum connection from EGR-check engine light and finally decided introducing 400-500 degree "dirty" exhaust did not make sense and would effect engine performance. I have never subscribed to the notion that EGR gases have a "cooling" effect on the intake charge and dirty hot exhaust gas was not detrimental to the engine's driveability, performance, and mileage. Went to Home Depot and capped the exhaust header source and the EGR inlet but left everything else intact-no check engine light. Result: Just passed state emissions inspection with zero effect on HC/NO at 2,500 RPM-ZERO (PPM and % are so low its laughable-HC was 6 PPM out of limit of 220 PPM!, engine has not pinged once since the block off of the EGR, throttle response is noticeably crisper, engine temp is noticeably LOWER on the gauge in all types of driving and gas mileage has gone UP along with power mid-high RPM. Only took me 21 years to solve the problem

 

you don't have to believe it, but if you understand the theory, you will see how the inert gas cools the combustion chamber and valves, it has to do with what is actually "in" (or isn't) the exhaust gas, NOT the temperature of the gas...

but like I said, many people block it off, myself included (actually I use a manifold without EGR on my small block). However knowing the effect it can have, you can tune for it with advanced timing and can make the same power with better fuel economy by making the engine more efficient. how much better is debatable...and I think it's easier to run without EGR, but you can't argue with physics, you can only choose to disbelieve.

 

400-500 degree intake temperature addition causes Knock in my mustang regardless of a "Cooling effect"...reality versus theory. EGR will hurt performance and mileage. My emissions was totally unaffected by the EGR deletion...again theory versus reality. There is a reason that every single engine builder I have ever asked about the EGR valve does NOT say, "Oh, if you have a pinging/knock from your higher compression or stock motor add an EGR valve for the "cooling effect" that the EGR valve will have on your combustion chamber temps"...NOT. Let's stop the nonsense about EGR's having no effect on driveability, performance, engine temps, and mileage. Does the EGR valve reduce NOx to some degree, YES (not in my Mustang though, probably because of the 4 cats )..no effect on emissions on a roller emissions test, no less..Fact. My HC/CO/NOx was WELL BELOW the limits for each. There is no getting around the actual results, physics or not.

 

sure there is, it's called scientific method. your reality does not prove correlation, only coincidence, and your talking a mustang with 4 cats and a likely completely different type EGR than a typical 70's vette...the OP asked how they worked, and who was running them and thoughts. Since this is a corvette forum, not a late model mustang forum, perhaps sharing information relative to a 70's small block chevy is a little more appropriate than obfuscating the poor guy with info about a computer controlled ford...

here's some reading for you , and I'm still NOT advocating using an EGR, just that they are highly misunderstood and blamed for things that are not truly related. note the bold, there are lots of variables that could be causing your issue.

"exhaust gas, added to the fuel, oxygen, and combustion products, increases the specific heat capacity of the cylinder contents, which lowers the adiabatic flame temperature.

In a typical automotive spark-ignited (SI) engine, 5% to 15% of the exhaust gas is routed back to the intake as EGR. The maximum quantity is limited by the need of the mixture to sustain a continuous flame front during the combustion event; excessive EGR in poorly set up applications can cause misfires and partial burns. Although EGR does measurably slow combustion, this can largely be compensated for by advancing spark timing. The impact of EGR on engine efficiency largely depends on the specific engine design, and sometimes leads to a compromise between efficiency and NOx emissions. A properly operating EGR can theoretically increase the efficiency of gasoline engines via several mechanisms:
Reduced throttling losses. The addition of inert exhaust gas into the intake system means that for a given power output, the throttle plate must be opened further, resulting in increased inlet manifold pressure and reduced throttling losses.
Reduced heat rejection. Lowered peak combustion temperatures not only reduces NOx formation, it also reduces the loss of thermal energy to combustion chamber surfaces, leaving more available for conversion to mechanical work during the expansion stroke.
Reduced chemical dissociation. The lower peak temperatures result in more of the released energy remaining as sensible energy near TDC (Top Dead-Center), rather than being bound up (early in the expansion stroke) in the dissociation of combustion products. This effect is minor compared to the first two."