Fuel injection for 351M
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Fuel injection for 351M
78bronco,
I don't know of any fuel injection system made specifically for the 351M/400 engines.
You can check out the Holley website and look at their Pro-Jection systems. You can use a throttle body system like that to replace the carburetor.
If you want to get anything more sophisticated (i.e., port injection), you're looking at custom design/fabrication and major $$$.
BubbaF250
1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.
I don't know of any fuel injection system made specifically for the 351M/400 engines.
You can check out the Holley website and look at their Pro-Jection systems. You can use a throttle body system like that to replace the carburetor.
If you want to get anything more sophisticated (i.e., port injection), you're looking at custom design/fabrication and major $$$.
BubbaF250
1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Fuel injection for 351M
78bronco,
I don't know of anyone who's had much success with the Pro-Jection on a 351M/400. The few people I know who have tried it are not satisfied. P-J seems to take a lot of messing around and tweaking to get it set up (a lot more than a carburetor). Also, the 351M/400 Thermactor AIR system doesn't lend itself to using an EGO sensor to control A/F ratio (closed-loop feedback) while driving.
Maybe if you're really devoted to experimenting with fuel injection, and you have the patience to tune it and work out the bugs, it might be worthwhile.
Since I've seen good power results from the 400 with a decent carburetor, I'm inclined to believe that you wouldn't see much if any improvement over the performance of a good carb.
BubbaF250
1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.
I don't know of anyone who's had much success with the Pro-Jection on a 351M/400. The few people I know who have tried it are not satisfied. P-J seems to take a lot of messing around and tweaking to get it set up (a lot more than a carburetor). Also, the 351M/400 Thermactor AIR system doesn't lend itself to using an EGO sensor to control A/F ratio (closed-loop feedback) while driving.
Maybe if you're really devoted to experimenting with fuel injection, and you have the patience to tune it and work out the bugs, it might be worthwhile.
Since I've seen good power results from the 400 with a decent carburetor, I'm inclined to believe that you wouldn't see much if any improvement over the performance of a good carb.
BubbaF250
1980 F250 4x4 Custom, 351M/NP435/NP208/D44HD-TTB/D60-FF/3.55s 6750 GVW, Rust & White.
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
Fuel injection for 351M
>Also, the
>351M/400 Thermactor AIR system doesn't
>lend itself to using an
>EGO sensor to control A/F
>ratio (closed-loop feedback) while driving.
EGO sensor should go in the exhaust pipe close to the header. I know that one of the reasons Ford killed the M series was the limitations on installing a multi port system on an engine which has the AIR plumbed into the intake but I don't think it was an EGO issue.
I've heard the same things as you have about the Holley Pro Jection systems tho'. Too much hassle not enough increase in performance.
>351M/400 Thermactor AIR system doesn't
>lend itself to using an
>EGO sensor to control A/F
>ratio (closed-loop feedback) while driving.
EGO sensor should go in the exhaust pipe close to the header. I know that one of the reasons Ford killed the M series was the limitations on installing a multi port system on an engine which has the AIR plumbed into the intake but I don't think it was an EGO issue.
I've heard the same things as you have about the Holley Pro Jection systems tho'. Too much hassle not enough increase in performance.
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Fuel injection for 351M
[font size="1" color="#FF0000"]LAST EDITED ON 31-Jan-01 AT 11:22 AM (EST)[/font][p]>I know that one
>of the reasons Ford killed
>the M series was the
>limitations on installing a multi
>port system on an engine
>which has the AIR plumbed
>into the intake but I
>don't think it was an
>EGO issue.
bill,
The EGO sensor was the main issue.
The EGO sensor looks for O2 in the exhaust gas stream, which can exist for only one reason, lean A/F ratio (which leaves un-reacted atmospheric O2 in the exhaust gas). At stoichiometric or rich A/F ratio, there is no O2 in the exhaust.
For the EGO to work properly, any fresh air injected for AIR purposes must be introduced into the exhaust downstream from the EGO. The M-block system injects air into the exhaust right in the exhaust ports in the cylinder head, leaving nowhere downstream to place an EGO.
If you look at the Thermactor AIR system on EFI engines (or even pre-EFI, feedback carbureted engines), the AIR system uses external tubing to pipe the fresh air down to the cats, or just ahead of the cats, downstream of the EGO sensor.
BubbaF250
>of the reasons Ford killed
>the M series was the
>limitations on installing a multi
>port system on an engine
>which has the AIR plumbed
>into the intake but I
>don't think it was an
>EGO issue.
bill,
The EGO sensor was the main issue.
The EGO sensor looks for O2 in the exhaust gas stream, which can exist for only one reason, lean A/F ratio (which leaves un-reacted atmospheric O2 in the exhaust gas). At stoichiometric or rich A/F ratio, there is no O2 in the exhaust.
For the EGO to work properly, any fresh air injected for AIR purposes must be introduced into the exhaust downstream from the EGO. The M-block system injects air into the exhaust right in the exhaust ports in the cylinder head, leaving nowhere downstream to place an EGO.
If you look at the Thermactor AIR system on EFI engines (or even pre-EFI, feedback carbureted engines), the AIR system uses external tubing to pipe the fresh air down to the cats, or just ahead of the cats, downstream of the EGO sensor.
BubbaF250
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
Fuel injection for 351M
>
>The EGO sensor was the main
>issue.
>
>The EGO sensor looks for O2
>in the exhaust gas stream,
>which can exist for only
>one reason, lean A/F ratio
>(which leaves un-reacted atmospheric O2
>in the exhaust gas).
>At stoichiometric or rich A/F
>ratio, there is no O2
>in the exhaust.
So the systems which inject air into the exhaust manifold are non EGO systems?
>For the EGO to work properly,
>any fresh air injected for
>AIR purposes must be introduced
>into the exhaust downstream from
>the EGO. The M-block system
>injects air into the exhaust
>right in the exhaust ports
>in the cylinder head, leaving
>nowhere downstream to place an
>EGO.
>
>The EGO sensor was the main
>issue.
>
>The EGO sensor looks for O2
>in the exhaust gas stream,
>which can exist for only
>one reason, lean A/F ratio
>(which leaves un-reacted atmospheric O2
>in the exhaust gas).
>At stoichiometric or rich A/F
>ratio, there is no O2
>in the exhaust.
So the systems which inject air into the exhaust manifold are non EGO systems?
>For the EGO to work properly,
>any fresh air injected for
>AIR purposes must be introduced
>into the exhaust downstream from
>the EGO. The M-block system
>injects air into the exhaust
>right in the exhaust ports
>in the cylinder head, leaving
>nowhere downstream to place an
>EGO.
>
Trending Topics
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Fuel injection for 351M
>So the systems which inject air
>into the exhaust manifold are
>non EGO systems?
AFAIK, yes.
The EGO sensor must be located upstream from the air injection point, otherwise the O2 introduced by the AIR system would throw off the EGO reading.
The EGO/feedback system depends on detecting O2 only from a lean A/F ratio. If you introduce additional O2 before the EGO sensor, the system would continually try to enrich the A/F ratio to get close to stoichiometric combustion (based on erroneous EGO readings), and gas mileage would drop dramatically.
In fact, unusual poor gas mileage is often one of the symptoms of a defective EGO sensor.
BubbaF250
>into the exhaust manifold are
>non EGO systems?
AFAIK, yes.
The EGO sensor must be located upstream from the air injection point, otherwise the O2 introduced by the AIR system would throw off the EGO reading.
The EGO/feedback system depends on detecting O2 only from a lean A/F ratio. If you introduce additional O2 before the EGO sensor, the system would continually try to enrich the A/F ratio to get close to stoichiometric combustion (based on erroneous EGO readings), and gas mileage would drop dramatically.
In fact, unusual poor gas mileage is often one of the symptoms of a defective EGO sensor.
BubbaF250
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
Fuel injection for 351M
>The EGO sensor must be located
>upstream from the air injection
>point, otherwise the O2 introduced
>by the AIR system would
>throw off the EGO reading.
>
>
>The EGO/feedback system depends on detecting
>O2 only from a lean
>A/F ratio. If you introduce
>additional O2 before the EGO
>sensor, the system would continually
>try to enrich the A/F
>ratio to get close to
>stoichiometric combustion (based on erroneous
>EGO readings), and gas mileage
>would drop dramatically.
That's good to know because when I put the exhaust system on my truck I was considering adding bungs so that I could install EGO sensors to tune it. Since I'm keeping the EGR system on the truck to keep is as "legal" as possible while it still has to pass DEQ sniffer tests I'm going to have to factor in the air being pumped into the system upstream of the EGO. However since there won't be any automatic adjustment of the mixture I think it should still work.
>upstream from the air injection
>point, otherwise the O2 introduced
>by the AIR system would
>throw off the EGO reading.
>
>
>The EGO/feedback system depends on detecting
>O2 only from a lean
>A/F ratio. If you introduce
>additional O2 before the EGO
>sensor, the system would continually
>try to enrich the A/F
>ratio to get close to
>stoichiometric combustion (based on erroneous
>EGO readings), and gas mileage
>would drop dramatically.
That's good to know because when I put the exhaust system on my truck I was considering adding bungs so that I could install EGO sensors to tune it. Since I'm keeping the EGR system on the truck to keep is as "legal" as possible while it still has to pass DEQ sniffer tests I'm going to have to factor in the air being pumped into the system upstream of the EGO. However since there won't be any automatic adjustment of the mixture I think it should still work.
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Fuel injection for 351M
>Since I'm
>keeping the EGR system on
>the truck to keep is
>as "legal" as possible while
>it still has to pass
>DEQ sniffer tests I'm going
>to have to factor in
>the air being pumped into
>the system upstream of the
>EGO.
bill,
The EGR and AIR systems are independent. EGR does not affect the EGO sensor.
As for factoring in AIR input to exhaust gas, that would be pretty difficult, because the AIR system output is not metered or precisely controlled.
The only practical way to tune an M-block with an EGO sensor is to temporarily disable the AIR system. You do that by either removing the Thermactor pump drive belt or applying high vacuum to the Thermactor bypass valve.
BubbaF250
>keeping the EGR system on
>the truck to keep is
>as "legal" as possible while
>it still has to pass
>DEQ sniffer tests I'm going
>to have to factor in
>the air being pumped into
>the system upstream of the
>EGO.
bill,
The EGR and AIR systems are independent. EGR does not affect the EGO sensor.
As for factoring in AIR input to exhaust gas, that would be pretty difficult, because the AIR system output is not metered or precisely controlled.
The only practical way to tune an M-block with an EGO sensor is to temporarily disable the AIR system. You do that by either removing the Thermactor pump drive belt or applying high vacuum to the Thermactor bypass valve.
BubbaF250
New User
Joined: Nov 1999
Posts: 18
Likes: 0
Fuel injection for 351M
This may be a dumb question but... When you are talking about an AIR system are refering to an Smog Pump and related hardware? I have a 1978 Bronco also and it came without any type of AIR systems. Only an EGR valve. Would I have the same problems? ie sensor placement? Thanks for the help
Posting Guru
Joined: Aug 2000
Posts: 2,416
Likes: 4
From: PacNW
Fuel injection for 351M
[font size="1" color="#FF0000"]LAST EDITED ON 01-Feb-01 AT 04:01 PM (EST)[/font][p]>The EGR and AIR systems are
>independent. EGR does not affect
>the EGO sensor.
>
>As for factoring in AIR input
>to exhaust gas, that would
>be pretty difficult, because the
>AIR system output is not
>metered or precisely controlled.
>
>The only practical way to tune
>an M-block with an EGO
>sensor is to temporarily disable
>the AIR system. You
>do that by either removing
>the Thermactor pump drive belt
>or applying high vacuum to
>the Thermactor bypass valve.
Sorry, had my head up my @ss when I wrote that post. I know the EGR and AIR systems are independent of one another. I am keeping both systems on the truck however so your comment about disabling the AIR makes sense. I'm going to have to do some further research before I decide whether or not to put the EGOs in the pipes.
>independent. EGR does not affect
>the EGO sensor.
>
>As for factoring in AIR input
>to exhaust gas, that would
>be pretty difficult, because the
>AIR system output is not
>metered or precisely controlled.
>
>The only practical way to tune
>an M-block with an EGO
>sensor is to temporarily disable
>the AIR system. You
>do that by either removing
>the Thermactor pump drive belt
>or applying high vacuum to
>the Thermactor bypass valve.
Sorry, had my head up my @ss when I wrote that post. I know the EGR and AIR systems are independent of one another. I am keeping both systems on the truck however so your comment about disabling the AIR makes sense. I'm going to have to do some further research before I decide whether or not to put the EGOs in the pipes.
Posting Guru
Joined: Aug 2000
Posts: 1,127
Likes: 3
From: (near) Denver USA
Fuel injection for 351M
[font size="1" color="#FF0000"]LAST EDITED ON 02-Feb-01 AT 11:44 AM (EST)[/font][p]>When you are talking
>about an AIR system are
>refering to an Smog Pump
>and related hardware?
coloranger,
Yes. AIR is the abbreviation for Air Injection Reaction, and it refers to a system that pumps fresh air into the exhaust gas. It is purported to reduce HC emissions by providing additional O2 to encourage further combustion after exhaust gases leave the cylinder. It also provides an O2 source for the 2-way catalytic converter to promote catalyzation of CO and HC into CO2 and H2O.
Ford's brand name for their AIR system (particularly the air pump) is "Thermactor."
>I have a 1978 Bronco also
>and it came without any
>type of AIR systems. Only
>an EGR valve. Would I
>have the same problems?
No. EGR (exhaust gas recirculation) has no affect on the EGO (exhaust gas oxygen) sensor. The only problem is the AIR system, and then only when it injects fresh air into the exhaust gas upstream of the EGO sensor.
BubbaF250
>about an AIR system are
>refering to an Smog Pump
>and related hardware?
coloranger,
Yes. AIR is the abbreviation for Air Injection Reaction, and it refers to a system that pumps fresh air into the exhaust gas. It is purported to reduce HC emissions by providing additional O2 to encourage further combustion after exhaust gases leave the cylinder. It also provides an O2 source for the 2-way catalytic converter to promote catalyzation of CO and HC into CO2 and H2O.
Ford's brand name for their AIR system (particularly the air pump) is "Thermactor."
>I have a 1978 Bronco also
>and it came without any
>type of AIR systems. Only
>an EGR valve. Would I
>have the same problems?
No. EGR (exhaust gas recirculation) has no affect on the EGO (exhaust gas oxygen) sensor. The only problem is the AIR system, and then only when it injects fresh air into the exhaust gas upstream of the EGO sensor.
BubbaF250
New User
Joined: Mar 2001
Posts: 5
Likes: 0
Fuel injection for 351M
Hi...new guy here...I've got a 78 Bronco Custom, rebuilt 400 (351M conversion) with .519 lift/270 duration cam, not sure on the compression but it runs better on high-octane fuel, Edelbrock Performer intake, Holley 650 CFM 4BB carb and NP435.
I'm interested in fuel injection for 1) better performance at off-camber angles on rock piles and 2) better fuel economy on the road. I realize #1 is a more realistic result than #2. Has anyone tried the Howell system? They have a kit for Ford V8's. I've heard more bad than good about the Holley ProJection, and it appears Edelbrock's is Chevy-only. I know more and more folks are swapping late-model EFI engines into their older rigs, and I've considered it with an EFI 460. Problem is, I payed WAY more than I should have for this truck, mainly because of the (re)built engine, so I want to make the 400 work. I'm happy with the power, just not with the off-camber carb issues and MPG.
Just some thoughts...anyone else?
Bill
78 Bronco Custom
400, NP435
3" Rancho Suspension Lift
I'm interested in fuel injection for 1) better performance at off-camber angles on rock piles and 2) better fuel economy on the road. I realize #1 is a more realistic result than #2. Has anyone tried the Howell system? They have a kit for Ford V8's. I've heard more bad than good about the Holley ProJection, and it appears Edelbrock's is Chevy-only. I know more and more folks are swapping late-model EFI engines into their older rigs, and I've considered it with an EFI 460. Problem is, I payed WAY more than I should have for this truck, mainly because of the (re)built engine, so I want to make the 400 work. I'm happy with the power, just not with the off-camber carb issues and MPG.
Just some thoughts...anyone else?
Bill
78 Bronco Custom
400, NP435
3" Rancho Suspension Lift