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Topic: egr or no egr ?

in Forum: C3 Engines

egr or no egr ?

Posted: 1/18/08 5:44pm Message 1 of 16
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edgwood, MD - USA
Joined: 11/1/2007
Posts: 736
Vette(s): 1975 convertible,with the hard top and power streering.it a 350 L48 with auto trans. the color is light blue.
  After finding out I have a numbers matching car with the help of great people here on this site. I want to put the car back to the way it came from the factory. Where I'm confussed is there is no egr valve or emission equipment on the motor.I think some of it was takeen off to install the headers,however where the egr valve gose there is a plate bolted on and it looks like it came from the factory that way(the cover is painted  and it matchs the engine color) So my question is in 75 did all corvettes have egr valves.


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egr or no egr ?

Posted: 1/18/08 7:10pm Message 2 of 16
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Yep, egr was used on 75s. I got the same plate on my black 79 with headers. I put it on there myself. EGR is in my box-O-parts.
mkapp78792008-01-18 19:19:32


egr or no egr ?

Posted: 1/18/08 8:03pm Message 3 of 16
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
MIke is right...your car should have the EGR on it. I wouldn't bother installing if you have headers on it now. I'd wait until I put manifolds back on it(if that's what you're planning), and do it all at one time.


Joel Adams
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egr or no egr ?

Posted: 1/18/08 8:33pm Message 4 of 16
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Greensburg, IN - USA
Joined: 9/24/2003
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Vette(s): Previous: 1984 Silver / Charcoal Coupe, 1988 Maroon Coupe / 1989 Artic White Coupe / 2001 Speedway White Roadster / Present:1976 Stingray Black / Black, Auto, 350 slightly modified (355 hp) Luxor Wires Redline Tires. / 1989 Roadster Bright Red...
This post raises a question for me. My 76 has the EGR with headers on it. The EGR has 1 nipple with a hose running to a nipple in the front of the intake manifold next to the thermostat housing. Is this routed incorrectly ? The reason I ask is in reading the previous post indicates that stock exhaust manifold versus headers make a difference. This would not have any bearing in the way that my EGR is routed. Tuxblacray2008-01-18 20:34:11


egr or no egr ?

Posted: 1/18/08 8:39pm Message 5 of 16
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Lynn Haven, FL - USA
Joined: 12/8/2007
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Vette(s): 1980 Frame Off Restore, Gun Metal Grey with Dark Red interior. 350 four bolt with forged pistons, Crane Cam, 1990 Tuned Port Injection System, Headman Elite Headers. Fairbanks Automatics, Detroit Locker Rear, High Performance Suspension.

My 80 came the same way. Headers with EGR. It was a piece of crap but I am now doing a frame off on it and should be complete in April. Should I remove the EGR?




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egr or no egr ?

Posted: 1/18/08 8:58pm Message 6 of 16
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The EGR will still operate with headers. It's basically a valve that allows heated air into the intake. In my case, when I installed the headers, I pulled the AIR pump and system, the EFE and just figured I'd pull the EGR, too.
Now, the EFE is useless with headers as there's no heat riser valve then.



egr or no egr ?

Posted: 1/18/08 9:08pm Message 7 of 16
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Duncanville, TX - USA
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Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas
You can run the EGR with headers...it just doesn't operate as efficiently to do it that way. The idea of the EGR is to re-route some of the burned(inert) fumes back into the intake, to help lower the cylinder temps to keep detonation(pinging) from being a major issue, AND reduce emissions.
Headers lower exhaust back-pressure, thereby reducing the amount of inert exhaust going back into the cylinder. It does still work...it doesn't actually hurt anything that I know of...just not sure if it is worth the extra heat on/in the intake manifold. Sorta a "benefit VS downside" thing.
I personally would not run an EGR set-up with headers, but it's just a preference of mine.


Joel Adams
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egr or no egr ?

Posted: 1/18/08 9:21pm Message 8 of 16
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Greensburg, IN - USA
Joined: 9/24/2003
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Vette(s): Previous: 1984 Silver / Charcoal Coupe, 1988 Maroon Coupe / 1989 Artic White Coupe / 2001 Speedway White Roadster / Present:1976 Stingray Black / Black, Auto, 350 slightly modified (355 hp) Luxor Wires Redline Tires. / 1989 Roadster Bright Red...
Well crap I am going to have to go to the speedshop to get a definative decision made. I originally thought the EGR would be a good thing if I ran it because in design it would do as Joel said.

That was before I thought about how my hoses were routed. At this point I don't think there is much value to it. But need that boast of reassurance.

Fortunitly I have both styles of Edlbrock Performer Intakes in my garage. 2101 non EGR & 3701 EGR.

I know that I can slap on the 3701 and it will run fine because the current stock intake runs fine. question is will running the 2101 and removing the EGR will it run better or will there be no noticable change.....
Tuxblacray2008-01-18 21:24:26


egr or no egr ?

Posted: 1/18/08 10:10pm Message 9 of 16
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You won't notice any difference.


egr or no egr ?

Posted: 1/19/08 5:57am Message 10 of 16
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Greensburg, IN - USA
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Vette(s): Previous: 1984 Silver / Charcoal Coupe, 1988 Maroon Coupe / 1989 Artic White Coupe / 2001 Speedway White Roadster / Present:1976 Stingray Black / Black, Auto, 350 slightly modified (355 hp) Luxor Wires Redline Tires. / 1989 Roadster Bright Red...
Thanks Mike, Between your and Joels advice I think I will go with the 2101. If for no other reason it allows me to remove some hardware and a hose to give the intake a cleaner look.


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