Yup, there you have it.

 

Well stated. Today's engines are totally different and I would not and have not ever removed the EGR valve on a modern engine. The 70's engines were completely bastardized to meet the emissions regulations and as I and others have said countless times before, an EGR valve is totally useless on the older engines and are not worth the hassle. LEAVE IT OFF!

Both my 73 NOVA SS and the my 78 vette ran sooo much better once the EGR valves were removed. For heaven's sake, most of us drive our C3's so infrequently that the whole emissions issue is totally rediculous!

 

Leaving aside the quality of mid 70's emissions equipment, theoretically an EGR will reduce performance, in that it displaces a minute amount of A/F mixture with essentially inert gas.

That said, the performance gain/loss is probably less than the margin of error in the most precise chassis dyno you can think of. Furthermore, the fact that performance engines are built without them is a Red Herring, performance engines are not built to comply with emissions requirements.

Modern OEM performance engines of course have EGR, the function is exactly the same, it injects a minute amount of recirculated exhaust gasses, the effect would be the same.

There is no harm in removing it if you are not required to comply with emissions tests, there is not enough harm in having one if you must comply.

My 78 L-82 ran fine with an EGR, my modified roller cammed aluminum head motor making 100hp+ more than the L82 runs just fine with one.

 

I removed the EGR on my '99 Silverado and its run fine for the last 100,000 miles without it.

 

I left my EGR on my car for the last 140,000 miles and it runs fine with it.

 

EGR is not a bad thing, especially if it's not a pain in the *** to get at.

The crappy thing about EGR is that it really limits the selection of cylinder heads and intake manifolds you can use in a performance build.

 

It seems to me an EGR valve is basically a vacuum leak. I can't imagine how the lean mixture created by opening the EGR wouldn't lead to pinging. It sure did in my case. In a carbureted engine, there is no way to compensate for the lean mixture. With computer controlled fuel injection the injectors could compensate, but not with a carburetor. I still maintain EGR valves are not compatible with carbureted performance engines.

 

That is great point about the difference between a carb and fuel injected engine with egr valves!

 

I imagine one reason that it didnt lead to pinging is that these motors were generally low compression with wimpy advance curves, lets be fair a 77 L-82 is NOT a performance motor in the strictest sense of the word.

Once you modify one of these motors with higher compression and more aggressive timing curves you will indeed run into more situations where pinging may occur. However I think you are imagining the EGR dumping huge quantities of exhaust gas into the mixture.

Who here knows exactly how much the mixture is leaned? no conjectures, no guessing... who actually knows? We can say all ww want that the mixture is leaned so much that pinging must be the natural ineluctable consequence, but without really knowing its all just guesswork.

Since these cars didnt run like crap from the factory, I find it impossible to swallow that EGR must cause motors to ping and run like crap.

Ultimately the OP's question of what performance gain is to be had in a factory 77 L-82 can be found by removing the EGR? Assuming the system is working properly, essentially none. Of course if its stuck open there will be benefit, but not because of weakness of the EGR system in general.

 

this is a neutral system-it neither helps nor hinders performance. It does, in fact, cool the combustion chamber so that you have less of a tendency for ping...

You will notice no performance hit for having it connected, and no performance increase for removing it. Edelbrock sells intake manifolds that will allow you to use the egr- that is what I use on my engine.

 

If EGR does not affect preformance, why did all these cars become such dogs when it was interduced? They were making big horsepower in the earlier years without it.

 

Primarily to meet upcoming pollution regs and the introduction of low octane unleaded gas, engine compression was drastically reduced and timing curves/carb tuning that favoured emissions compliance rather than performance.

The EGR system costs zero performance and the extra evil AIR system somewhere around 1 HP.

 

The big horsepower numbers were not all that great if you take into consideration that they used SAE as opposed to net horsepower. First they de-tuned the engines, thats why recurving the distributor and adjusting the timing adds so much more horsepower. Then they chocked the exhaust with single exhaust and a cat. Replace the exhaust sytem, tune the car priperly and there will be little difference between actual horsepower numbers at the rear wheels.An example, 1970 LT-1 rated at 370 horses, in 1971 it was down to 330, 1972 down top 255. Same engine, different math!

 

There were many reasons for the lower horsepower numbers. Yes there was a change from gross figures to net, but there was a drop in real performance as well. The addition of the EGR valve was just part of the problem. The drop in horsepower was also due to a drop in compression and the addition of catalytic convertors that didn't flow as well as modern ones do. Not to mention the insurance companies were putting pressure on the manufacturers to reduce performance.

I tried for years to get my car to run with the EGR working and finally gave up. I have been working on chevy small blocks for 35 years and like to think I'm reasonably good at it, but I could never get the engine to run consistently well with the EGR hooked up. With computerized fuel injection it can probably be done but there is no way to get the mixture dialed in with a carburetor with the EGR continually dumping exhaust gases into the mixture.

 

Good discussion but I would NOT add an EGR valve again to an engine unless you HAVE to for emissions reasons-inspection! One can argue the pros and cons all day long about the difference in performance which is probably negligible but if I had to bet the farm on whether an EGR valve increases or decreases performance, no matter how small, I'll go with the overall effect is probably negative, not positive, on a carbureted engine, not fuel injection.

Again, in theory, the EGR is neutral, but in the real world that is simply not true, especially in terms of actual driveability-simply NOT true.

BTW-there are countless folks who run just high flow cats on their dual exhaust, and almost always pass the sniffer test WITHOUT an EGR valve. The EGR valve is only needed for the cleanup of the exhaust where very little trace of NO is required.

The emission's argument reminds me of the recent decree that CO2 is a deadly gas by our beloved EPA, not carbon monoxide, but C02! Oh really, the last time I looked every living breathing animal on earth ingest O2 and emitts C02 which is taken up by plants and converted back to O2-a deadly gas? How about this one? I just read in a MAJOR national paper-you need to be concerned about the exhaust on your 2009 Jeep because it contains carbon monoxide which is deadly-Oh really, every modern car's exhaust is basically C02 and water. We can't even get the basic biology correct!

Ok-I am done. Leave off the EGR valve on your 500 miles per year driven C3 in my opinion-the world has much bigger fish to fry!

 

If there weren't emission laws, there would be no EGR valve. The engineer's came up with this partial solution to reduce emissions. It's just one more component on an engine that can go wrong and often does. If you eliminate it, one less component to worry about. If the EGR added to performance, serious builders would put one on. And most guys looking for more performance will follow what the engine builders are doing. If any engine component doesn't add to the overall performance of an engine, then why put it on in the first place? To qualify that statement, it's directed at the guys who seek performance and not originality.

 

(I'm in Alabama so no legal worries)

So the whole decline in horsepower was the EGR valve?

I had a 76 Grand Prix that pinged as soon as I gave it the pedal and I hooked the EGR valve up and it wouldn't ping even at full throttle.
But I beleive if I would have changed out the crappy intake and carburetor it would have solved alot of problems.