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Exhaust Gas Recirculation. You have an EGR valve that puts some exhaust from themanifold back into the intake for some damn polution reason. At least thats what I THINK i remember.
 

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You do not need EGR for anything but emmision reasons. If you have an EGR manifold just make yourself a block off plate, or just ubhook the vacuum hose going to it. That will render it useless. As far as I am concerned the best place for a EGR valve is in the trash can.

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350 4speed 12bolt 3.73's
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A properly functioning EGR valve has NO effect on performance. At WOT there is no vacuum to operate the EGR valve, therefore there is no EGR at wot.

Don't be surprised if you get detonation if you eliminate the EGR valve and run the same spark curve. EGR is operational at light load/cruise so more spark advance is provided for those points.
 

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EGR can be a good thing at times. Way back in the middle 70s before a lot of you were born we did some extensive testing on high performance VW engines. By introducing some egr under a load in controlled amounts we were able to brig detination way down. It resulted in as much as a 10 horsepower increase on the engine dyno. It helps to cool the combustion mixture similar to a cold air induction system. Indy cars used EGR for years and still may I'm not sure! We used the egr valves we developed for years in off road applications! Strange as it may seem the smog boys did us some good! Mark

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65SS Malibu ZZ502/200R4/9inch
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I concure that the EGR was introduced to cool down the combustion temp. slightly, thus lowering NOx emmisions; this desired (from an emissions point of view) lower combustion temp. is another reason why compression ratios were dropped in the early seventies. Burned exhaust gas can't burn again so it reduces the intensity of the burn in the combustion chamber (o.k. it reduces efficiency to a point). Also, if anything does remain unburned in the combustion process then a small portion of it has a second chance at burning cleanly and therefor potentially lower oxides of nitrogen emmisions.
Much of this crap and more appeared on 1973 cars. Of course efficiency and performance hit a low that year as did fuel economy. In retrospect we can chalk it up to early growing pains in the fight to lower emissions.
Catalytic converters, computer controls, oxygen sensors and EFI have largely rendered much of this stuff as obsolete, but as the 'car-ignorant' demand increasingly lower emissions (nothing wrong with clean air but how many thousands per car for miniscule benefit can we bear?) then everything has to be explored and re-evaluted. Reformulated gas with low sulphur can improve every car's emission output.
 

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If you guys think EGR is so wonderful, why do I not see it on any HP motors? or retrofoitted into your cars. The reason I had to deal with one is the late model stock alum manifold I swapped onto my car had a nasty bulbous growth poking off of it. My previous statment still stands that as far as I am concerened they belong in the trash can.

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350 4speed 12bolt 3.73's
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AMEN!

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Tom Parsons
 

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People often revile what they do not understand. I am not saying that "EGR is so great." I will say though, that it is not the villian that everyone makes it out to be. EGR has a minimal effect at part throttle because extra spark advance is administered to compensate for it. ******So as long as it is adminstered as part of an engineered system it is relatively painless.****** In fact, in the laboratory I have been able to run an engine leaner than 20:1 A/F by retarding the valve timing and using approx 15% EGR. Don't be surprised if you see this in the future on production vehicles as a way to further increase mileage.

The effect (provided the valve is working correctly) on wide open throttle performance is nil once again, because no vacuum is provided to the EGR valve at that time.
 

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Unklepennybags? Do you have an EGR on your car?

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350 4speed 12bolt 3.73's
Bench Blue w/black inter. [email protected]
 

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Yep, I kept it on my Trans-Am, 400 small block Chevelle, and my Chevrolet Impala. Not on my '67, but then again it didn't come with it.

Mike
 

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My truck has the manifold with the passage under it that meeters it through little orfices in the botom of the manifold....no valve....dont forget that type. And not to really get into an argument but heat=power and I cant see how diluting the mixture increases power, it might not hurt things that bad but I cant see how it could help. Its impact is minimal though. But I do know if you just yank it and dont do anything else it will probably have a negative effect. If it aint broke why fix it?
 
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