Egr system help
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8th Gear
Joined: Mar 2024
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Egr system help
Hey everyone! Working on my 1979 f150 with the 351m. So I’m currently in the process of removing all of the old vacuum lines for evap/egr. (Half the lines were rotted and plugged.) however I have read that due to the factory timing chain setup and factory carb, removing egr will cause pinging. I still have the diaphragm for the egr, and as far as I can tell, I should be able to just hook the egr up to one of the green coolant temp sensors, and connect the sensor to the ported vac? Maybe I’m completely wrong. My ultimate goal is to simplify as much as possible and remove as much as I can. Thanks!
Hotshot
Joined: Jul 2020
Posts: 10,315
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From: Near Salt Lake City
It does need to run through a TVS or ported vacuum switch as the EGR should not operate cold
Above and below 5000 feet in elevation was a difference in the vacuum schematics on those older ones
Most of those Thermal Vacuum Switches are no good by now and you have to work around those as they are about impossible to get new ones
Above and below 5000 feet in elevation was a difference in the vacuum schematics on those older ones
Most of those Thermal Vacuum Switches are no good by now and you have to work around those as they are about impossible to get new ones
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8th Gear
Joined: Mar 2024
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Oh okay thanks! So if you think the thermal vacuum switches are bad, what could I use as a replacement? I’m sure there must be a digital style vacuum switch I could setup? Or is there any “easy” way to run it without the use of the thermal switches?
Hotshot
Joined: Jul 2020
Posts: 10,315
Likes: 2,579
From: Near Salt Lake City
No, not bad necessarily, you should test them
You only need one or two working for the EGR and the vacuum advance
Maybe a delay valve or two
Do you have a VECI on one of the valve covers showing the vacuum routing?
You only need one or two working for the EGR and the vacuum advance
Maybe a delay valve or two
Do you have a VECI on one of the valve covers showing the vacuum routing?
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8th Gear
Joined: Mar 2024
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Oh okay! And unfortunately no diagram on my valve cover but I have found the diagram online for all the routing, the egr system as far as I can tell is pretty simple, just a bit confusing since it shares a vacuum T to feed other vacuum systems. But yeah if you could find that diagnostic information that would be super helpful thank you!
5th Wheeling
Joined: Mar 2024
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'77 F150 351M : I removed all the EGR off my pickup about 20-25 years ago. You can see were I filled-in with some JB weld epoxy. There is a corresponding port in the intake manifold that has to be plugged also. It is directly underneath this carb spacer that feeds exhaust gases to the EGR valve, which then directs the gases through the slots that are filled with epoxy as shown. The plate on the back of the carb spacer with 3 screws is where your EGR valve mounts behind the carburetor. I have a 2150 carb that seems to work just fine, and have never experienced "pinging" with the EGR system removed...but I would like to know where you read about the "cam timing chain" issue with these '70's 351M engines w/EGR. (My 351M is apart right now for a reason, and when I explained the heavy carbon "coking" build-up all through my intake ports and intake valves, It was mentioned that I had a "timing" issue ... and so just maybe I have some consequential experience now ... and perhaps I'll need to get rid of the cam along with that EGR I gutted...?? )
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Hotshot
Joined: Jul 2020
Posts: 10,315
Likes: 2,579
From: Near Salt Lake City
Sorry, I have not got back yet with some emissions components diag
The whole book will be hard to post
Maybe take a few pics of the wax valves you have, like the ones in the air cleaner and the ones on the intake manifold and thermostst housing
Any idea of whether it is a CA emissions truck? or not?
The whole book will be hard to post
Maybe take a few pics of the wax valves you have, like the ones in the air cleaner and the ones on the intake manifold and thermostst housing
Any idea of whether it is a CA emissions truck? or not?
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8th Gear
Joined: Mar 2024
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'77 F150 351M : I removed all the EGR off my pickup about 20-25 years ago. You can see were I filled-in with some JB weld epoxy. There is a corresponding port in the intake manifold that has to be plugged also. It is directly underneath this carb spacer that feeds exhaust gases to the EGR valve, which then directs the gases through the slots that are filled with epoxy as shown. The plate on the back of the carb spacer with 3 screws is where your EGR valve mounts behind the carburetor. I have a 2150 carb that seems to work just fine, and have never experienced "pinging" with the EGR system removed...but I would like to know where you read about the "cam timing chain" issue with these '70's 351M engines w/EGR. (My 351M is apart right now for a reason, and when I explained the heavy carbon "coking" build-up all through my intake ports and intake valves, It was mentioned that I had a "timing" issue ... and so just maybe I have some consequential experience now ... and perhaps I'll need to get rid of the cam along with that EGR I gutted...?? )
hope this helps!
Also I will try and get some pictures up soon of the stuff I have!
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