Emissions Questions
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Senior User
Joined: Dec 2003
Posts: 119
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From: Denver Colorado
Emissions Questions
Just bought a 1977 F-150 4x4 351M engine and am trying to get it up to emissions standards. Right now it has the vacuum advance line and that is it, the Holley 2bbl didn't even have the choke plate on it.
To get emissions in CO I need: EGR, Evap system, air pump, and PVC but no cat.
Questions. The thick gasket under the EGR does not have a hole in it to let gasses pass between the intake and spacer, should it? It looks like it should but the carb kit I bought does not have a hole in any of the gaskets.
Both of my manuals show the evaporative canister mounted on the frame, I am pretty sure this truck came with the coffee can mounted next to the battery by the look of the mounting plate, does this system have the same routing as the one on the frame mount?
Finally, for the air pump, where do the air manifolds go into the engine on the 351 modified. My Chilton's shows the exhaust manifolds but I don't see any place for them to go there or into the heads.
Thanks for any help.
To get emissions in CO I need: EGR, Evap system, air pump, and PVC but no cat.
Questions. The thick gasket under the EGR does not have a hole in it to let gasses pass between the intake and spacer, should it? It looks like it should but the carb kit I bought does not have a hole in any of the gaskets.
Both of my manuals show the evaporative canister mounted on the frame, I am pretty sure this truck came with the coffee can mounted next to the battery by the look of the mounting plate, does this system have the same routing as the one on the frame mount?
Finally, for the air pump, where do the air manifolds go into the engine on the 351 modified. My Chilton's shows the exhaust manifolds but I don't see any place for them to go there or into the heads.
Thanks for any help.
Tuned
Joined: Mar 2010
Posts: 491
Likes: 7
Just bought a 1977 F-150 4x4 351M engine and am trying to get it up to emissions standards. Right now it has the vacuum advance line and that is it, the Holley 2bbl didn't even have the choke plate on it.
To get emissions in CO I need: EGR, Evap system, air pump, and PVC but no cat.
Questions. The thick gasket under the EGR does not have a hole in it to let gasses pass between the intake and spacer, should it? It looks like it should but the carb kit I bought does not have a hole in any of the gaskets.
Both of my manuals show the evaporative canister mounted on the frame, I am pretty sure this truck came with the coffee can mounted next to the battery by the look of the mounting plate, does this system have the same routing as the one on the frame mount?
Finally, for the air pump, where do the air manifolds go into the engine on the 351 modified. My Chilton's shows the exhaust manifolds but I don't see any place for them to go there or into the heads.
Thanks for any help.
To get emissions in CO I need: EGR, Evap system, air pump, and PVC but no cat.
Questions. The thick gasket under the EGR does not have a hole in it to let gasses pass between the intake and spacer, should it? It looks like it should but the carb kit I bought does not have a hole in any of the gaskets.
Both of my manuals show the evaporative canister mounted on the frame, I am pretty sure this truck came with the coffee can mounted next to the battery by the look of the mounting plate, does this system have the same routing as the one on the frame mount?
Finally, for the air pump, where do the air manifolds go into the engine on the 351 modified. My Chilton's shows the exhaust manifolds but I don't see any place for them to go there or into the heads.
Thanks for any help.
The EGR probably doesn't have a hole in it because some people use a solid gasket with a thin plate to block off the EGR passage. If there's no hole, the exhaust gasses won't pass through, and you won't have EGR flow, which means that during the emissions tests, your numbers are gonna be high!
For the air pump...doesn't the air pump just add air into the exhaust near the H pipe? Not sure exactly on the 351, but I know on the 302 Mustangs (79-93) the air pump pushed extra volume in at the H.
~B
Senior User
Joined: Jun 2008
Posts: 383
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From: Aurora CO
have you actually taken it to be tested?
the reason i ask is because i live in aurora and have a similar truck. 78 f150 4x4 with a 400.
i'm fairly certain that i don't have the air pump on mine at all and i have had it pass the last 3 years.
not 100% certain but doesn't the gvwr also play a role?
the reason i ask is because i live in aurora and have a similar truck. 78 f150 4x4 with a 400.
i'm fairly certain that i don't have the air pump on mine at all and i have had it pass the last 3 years.
not 100% certain but doesn't the gvwr also play a role?
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Senior User
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From: Denver Colorado
The GVWR does play a role, I thought the f-150 was under 6,000 pounds which the guy said required all of this equipment but I did not have the numbers in front of me when I called the Colorado Clean Air technician who was actually very helpful. I have not had it tested, I was waiting to get temp tags after I had most of the emissions stuff on.
I may just connect the EGR and try it because the truck is pretty stock and I see no indication of the evaporative system or smog pump although I know a lot of this stuff was trashed immediately (my dad tore everything off of his when he got it in late 70's but that was when there were no emissions tests.)
Thanks
I may just connect the EGR and try it because the truck is pretty stock and I see no indication of the evaporative system or smog pump although I know a lot of this stuff was trashed immediately (my dad tore everything off of his when he got it in late 70's but that was when there were no emissions tests.)
Thanks
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Senior User
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From: Denver Colorado
Also was waiting until I rebuilt a carb and put it on, the other one was trashed.
I "installed" a hole in the EGR spacer and will run some basic vacuum lines and give it a shot.
I "installed" a hole in the EGR spacer and will run some basic vacuum lines and give it a shot.
Laughing Gas
Joined: Oct 2009
Posts: 873
Likes: 56
From: Merlin, OR
Emissions
I live in Denver, and I went to a place on East Colfax called 81 and Under Emissions, was 15 bucks. My emissions stuff was all intact, and it passed no problem, not sure how much of a stickler the guy is on the rules. One thing was slightly over and he adjusted the carb, and then it was fine. Might try him.
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From: Denver Colorado
thatsrealnice - when you say all of your emissions was intact do you still have the smog pump, vacuum canister, EGR, evaporative system, etc? I looked at my tag and the vehicle says it is 6150 GVWR, so I think according to Denver laws that may reduce some of the emissions requirements.
Thanks
Thanks
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Elder User
Joined: Jul 2005
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I had a 77 F1504x4 short box in 1979 and it had the 351 and it had no air pump. As for the GVWR it does play a roll in Denver. F100s had a pump and F150s did not in 77. I was told by the dealer that was Fords reason for the F150s, they could weigh in at 6050lbs and miss most of the emissions requirements for the 77 year. I have a 77 F250 4X4 now with a swapped in 1969 460 in it, bought it and it was 25 years old so I ran it down to envirotest and it passed no problem, heck that guy would have not know a 351 from a 460 as long as it passed he didn't care, ran right down and got a collectors plate for it. Now it is emissions exempt as long as I own it. If the guy on east Colfax is still there I would use him first, True old style tailpipe tester is a lot more forgiving than the test at envirotest.
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Thread Starter
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Senior User
Joined: Dec 2003
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From: Denver Colorado
I had a 77 F1504x4 short box in 1979 and it had the 351 and it had no air pump. As for the GVWR it does play a roll in Denver. F100s had a pump and F150s did not in 77. I was told by the dealer that was Fords reason for the F150s, they could weigh in at 6050lbs and miss most of the emissions requirements for the 77 year. I have a 77 F250 4X4 now with a swapped in 1969 460 in it, bought it and it was 25 years old so I ran it down to envirotest and it passed no problem, heck that guy would have not know a 351 from a 460 as long as it passed he didn't care, ran right down and got a collectors plate for it. Now it is emissions exempt as long as I own it. If the guy on east Colfax is still there I would use him first, True old style tailpipe tester is a lot more forgiving than the test at envirotest.
Thanks again for all the help.
New User
Joined: Jun 2010
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I had a 77 F1504x4 short box in 1979 and it had the 351 and it had no air pump. As for the GVWR it does play a roll in Denver. F100s had a pump and F150s did not in 77. I was told by the dealer that was Fords reason for the F150s, they could weigh in at 6050lbs and miss most of the emissions requirements for the 77 year. I have a 77 F250 4X4 now with a swapped in 1969 460 in it, bought it and it was 25 years old so I ran it down to envirotest and it passed no problem, heck that guy would have not know a 351 from a 460 as long as it passed he didn't care, ran right down and got a collectors plate for it. Now it is emissions exempt as long as I own it. If the guy on east Colfax is still there I would use him first, True old style tailpipe tester is a lot more forgiving than the test at envirotest.
Laughing Gas
Joined: Oct 2009
Posts: 873
Likes: 56
From: Merlin, OR
Collector plates
They did change the law on the collector plates, however, it is a rolling year thing, so in 2 years, your truck would be eligible for them, which I think means that emissions are only done every 5 years then. I honestly don't know if my truck has the air pump thing on it. Not even sure what it looks like. My truck was originally sold in Denver, so I'm sure any of the emissions stuff would have come with it.
Elder User
Joined: Jul 2005
Posts: 525
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Haven't hear about the rolling thing, but is 1975 and older, it use to be 25 years or older, and mine is grandfathered in under the new law, still a 5 year plate and as long as it is current no e-test needed to renew it. Made me mad when they changed it as my CJ7 is a year from 25 but as a 86 it will never see a collector plate.
Postmaster
Joined: Oct 2008
Posts: 3,026
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From: Renton, WA
Wow what kind of crazy state is CO that you have to have all that stuff working on a 77? And really even if the law says so, how they gunna know?
I ripped all that stuff off my 87 and even in liberal Seattle I passed no problem. I have no idea what the law specifies but I know what they look for. They just test the exhaust, the testers don't know what a freak'n EGR valve or AIR pump are.
I ripped all that stuff off my 87 and even in liberal Seattle I passed no problem. I have no idea what the law specifies but I know what they look for. They just test the exhaust, the testers don't know what a freak'n EGR valve or AIR pump are.
Elder User
Joined: Jul 2005
Posts: 525
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Yes Opossum, it is a money maker here in the Denver area, They have been talking about doing away with it all together, they say that car emissions are down so low that it is not worth the effort to even test anymore. Then now they want to expand the test area to all of Boulder and weld county. Yea it is coming. Kinda like California jr, Hell we have our own country right here in Colorado so why not. lol.