Crossover and EGR question
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
Crossover and EGR question
Putting on a manifold with EGR to pass inspection. If I block the crossovers with the block off plates. Does that render the EGR inoperative even though it looks functional? Kinda like a little emissions control christmas ornament?
Drifting
Joined: Apr 2008
Posts: 1,305
Likes: 2
From: Lewisburg WV
thegazman
The EGR (exhaust gas recirculator) valve recirculates exhaust gas into your fresh air at higher engine RPM's. It will idle extermely rough if it sticks open at idle. Blocking the passage to the EGR will shut off the exhaust recirculation.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
Not going to block the passage to the EGR. I want to block the atual crossover in the manifold under the carb which should eliminate any exhaust even getting to the EGR. I think. Thats the actual question.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
You are dealing with two separate passages. The crossover for engine warmup directs exhaust gases from the passenger side to the driver's side when the engine is cold and heat riser valve closed. That passage is under the carb and is not linked to the combustion process. That is the passage that can be closed with the SS tangs on some intake gaskets.
The EGR passage is separate and is linked to air and fuel intake under certain conditions. For example on my 1974 it is controlled by a thermal vacuum switch (TVS) and engine vacuum. It is closed when the engine is cold and even when warmed up, it is closed at idle (determined by the connection to a ported carb spout).
In other words you can have a fully functioning EGR with a blocked off crossover passage.
The EGR passage is separate and is linked to air and fuel intake under certain conditions. For example on my 1974 it is controlled by a thermal vacuum switch (TVS) and engine vacuum. It is closed when the engine is cold and even when warmed up, it is closed at idle (determined by the connection to a ported carb spout).
In other words you can have a fully functioning EGR with a blocked off crossover passage.
Last edited by Paul L; Sep 12, 2010 at 12:55 PM.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
Thats what I thought too. But where does it get exhaust to recirculate if the crossover is blocked? The intake manifold gasket blocks those egr ports (check em out) even without the blocking plates. I blew smoke into the passages and if you block the crossover the EGR cannot get exhaust to inject anywhere therefore making it null whether its on, off or indifferent, I THINK.
Last edited by micks69; Sep 12, 2010 at 04:43 PM.
Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Thats what I thought too. But where does it get exhaust to recirculate if the crossover is blocked? The intake manifold gasket blocks those egr ports (check em out) even without the blocking plates. I blew smoke into the passages and if you block the crossover the EGR cannot get exhaust to inject anywhere therefore making it null whether its on, off or indifferent, I THINK.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
Paul,
Don't cut them out they go nowhere and you will have a huge manifold leak. When blowing the smoke thru the cross over it will come out the egr ports, the other crossover and inside the manifold. Therefore they all are connected somewhere underneath. Still think if you block the crossovers, no exhaust, means EGR does nothing. This is only cause I'm too cheap to replace the heat shield underneath, or the manifold and its warm here most of the time.
Don't cut them out they go nowhere and you will have a huge manifold leak. When blowing the smoke thru the cross over it will come out the egr ports, the other crossover and inside the manifold. Therefore they all are connected somewhere underneath. Still think if you block the crossovers, no exhaust, means EGR does nothing. This is only cause I'm too cheap to replace the heat shield underneath, or the manifold and its warm here most of the time.
Last edited by micks69; Sep 12, 2010 at 06:34 PM.
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Team Owner
Joined: Aug 1999
Posts: 30,995
Likes: 98
From: Ontario
Paul,
Don't cut them out they go nowhere and you will have a huge manifold leak. When blowing the smoke thru the cross over it will come out the egr ports, the other crossover and inside the manifold. Therefore they all are connected somewhere underneath. Still think if you block the crossovers, no exhaust, means EGR does nothing. This is only cause I'm too cheap to replace the heat shield underneath, or the manifold and its warm here most of the time.
Don't cut them out they go nowhere and you will have a huge manifold leak. When blowing the smoke thru the cross over it will come out the egr ports, the other crossover and inside the manifold. Therefore they all are connected somewhere underneath. Still think if you block the crossovers, no exhaust, means EGR does nothing. This is only cause I'm too cheap to replace the heat shield underneath, or the manifold and its warm here most of the time.
Good luck with whatever you are attempting to do. I am out of this thread.
Thread Starter
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
I'm trying pass inspection in NC and the stuff needs to be on the car but doesnt have to neccessarily work.
Sorry Paul but the EGR must be used with the crossover there is physically no ther way for exhaust gas to get to the valve. Its really just a special application for me a udget build a 77 that I've spent too much on already. I dont want spend $20 for a TVS and $20 for an EFE if they wont do anything, have two that are non functional and will be just fine with a blocked crossover as the EGR will be non functional without it. Good luck with your build up.
Sorry Paul but the EGR must be used with the crossover there is physically no ther way for exhaust gas to get to the valve. Its really just a special application for me a udget build a 77 that I've spent too much on already. I dont want spend $20 for a TVS and $20 for an EFE if they wont do anything, have two that are non functional and will be just fine with a blocked crossover as the EGR will be non functional without it. Good luck with your build up.
