TCCoA Forums banner

1 - 15 of 15 Posts

·
Registered
Joined
·
2,638 Posts
Discussion Starter #1
I have a 302 out of a '93LX Thunderbird that is sitting in my '73 F100. I plan to use long tube headers but I am unsure if they will be compatible with O2 sensors. I have no qualms about having bungs welded to the headers but do they need to be the same distance from the exhaust ports as the original manifolds? If so, then it would place them somewhere on the individual exhaust runners before the collector. That won't work, will it?
 

·
Registered
Joined
·
2,638 Posts
Discussion Starter #2
Bump.
 

·
Registered
Joined
·
1,716 Posts
Sean Hyland Motorsports recomends the sensor be placed in one of the primary tubes as close to the cylinder head as possible instead of down in the collector of long tube headers. Even though it reads only one cylinder, the response of the engine is better and driveability greatly improved.....Ford uses this idea on the Contour SVT.
 

·
Registered
Joined
·
2,638 Posts
Discussion Starter #4
No kidding? I always thought it needed to read from all the cylinders.
Does it matter which tubes they go on? Will the EEC need tuning?
 

·
Registered
Joined
·
1,716 Posts
Something about it taking longer for things to get up to temp down in the collector of long tube headers and until then the engine stays in Open Loop.

Obviously, either place will work....it seems that having it as SHM recommends will get the motor running in Closed Loop mode a bit sooner to enhance driveability.
 

·
Registered
Joined
·
1,716 Posts
Hearing that Sean Hyland recommends it makes me question that whole thing. Are they not heated O2 sensors?
Got me thinking so I went back into his book for a little more digging....hopefully we come correct.

First:
"The cast iron manifold retains heat in the exhaust system, helping to light off the catalytic convertor quickly......Typically, this light-off takes 30-45 seconds, and keeping light-off to a minimum is why Ford has placed one of the catalytic convertors so close to the manifold."
- page 71 of "How to Build Max-Performance 4.6-Liter Ford Engines" by Sean Hyland

Then this part will make more sense:
"Most [long tube] header manufacturers place the oxygen sensor bung into the collector, believing that the exit of the 4 primary tubes is the best location to pick up the exhaust reading. Unfortunately, the collector on a long tube header takes forever to get up to operating temperature. The engine operate in open loop until the oxygen sensor is up to temp, and even then the sensor is so far away from the engine much like a long distance telephone call. We have taken to moving the oxygen sensor up into one of the primary tubes, as close to the cylinder head as possible. While it is true that we only see one cylinder, the response of the engine is much better, and driveablity is much improved. Ford used this technique on the Contour SVT."
- page 72 of "How to Build Max-Performance 4.6-Liter Ford Engines" by Sean Hyland

Does that help? :)
 

·
Registered
Joined
·
893 Posts
I understand the concept, but do not understand the actual problem if you're dealing with heated O2 sensors. It sounds like a solution looking for a problem, to me.
 

·
Newbie
Joined
·
5,650 Posts
I've been thinking about this and can't figure out if you will have a problem or not. There are several things to consider here.

1) The computer has a oxygen sensor transport delay table that basically specifies the delay between the time the gas is expelled from the cylinder and the time it reaches the sensor. It is a function of engine RPM. That said, placement of the oxygen sensor in terms of distance from the exhaust port does matter.

2) With only one cylinder to sample from, the oxygen sensor will (theoretically) be responding to changes at 1/4 the frequency it normally would. I'm sure this isn't hard to see. Now the computer controls the fuel trim on an entire side of an engine, so as long as the computer doesn't feel like the sensor is responding too slowly due to the aforementioned thing, it shouldn't be a problem.
 

·
Registered
Joined
·
2,638 Posts
Discussion Starter #10
So you are saying each should go in one of the primary tubes the same distance from the exhaust port as the original manifolds.
Do you think it matters which primaries they are installed into?
 

·
Registered
Joined
·
892 Posts
On my sons Mustang with 1 5/8's long tubes we just changed the start routine in the tune. Added 30 seconds b4 it goes closed loop. Stock was 45 seconds. No more problems. My 1st question would be though is have you tried it? May not even be an issue. On his he just went rich for about 60 seconds by the time it cleared. It was changing the short term trims though.
 

·
Registered
Joined
·
2,638 Posts
Discussion Starter #12
...My 1st question would be though is have you tried it? May not even be an issue...
That's the thing. This is a budget swap. I am using the entire wire harness from the '93 in the truck, from the headlights to the interior, so it is practically plug-n-play. The driveshaft and the exhaust is the only thing that I really need to buy. I don't plan to get a tune so I don't want to buy the headers and have them modified only to find that I need a tune. I will go with the Thunderbird manifolds and cut the frame to make them fit before spending hundreds of dollars on a tune.
 

·
Registered
Joined
·
892 Posts
That's the thing. This is a budget swap. I am using the entire wire harness from the '93 in the truck, from the headlights to the interior, so it is practically plug-n-play. The driveshaft and the exhaust is the only thing that I really need to buy. I don't plan to get a tune so I don't want to buy the headers and have them modified only to find that I need a tune. I will go with the Thunderbird manifolds and cut the frame to make them fit before spending hundreds of dollars on a tune.
Wow, you would have to cut the frame for the stock tubes? I am assuming you are refering to the kmember? Maybe look at the Mustang shorties, they exit more to the rear than the TBird header. You can even get equal length in Mustang shorties. The stock TBird headers are really pinched on two cylinders. Just thinking outloud.
 

·
Registered
Joined
·
2,638 Posts
Discussion Starter #14
Wow, you would have to cut the frame for the stock tubes? I am assuming you are refering to the kmember? Maybe look at the Mustang shorties, they exit more to the rear than the TBird header. You can even get equal length in Mustang shorties. The stock TBird headers are really pinched on two cylinders. Just thinking outloud.
Yup, the factory Tbird passenger side manifold just touches the frame but clears the engine cradle. Might be able to install without cutting but the bolts would be a pain to install/remove. Also, the exit opening for the manifold sort of points at the frame making it tight. I am tired of having to cram my hands into small places every time I want to work on my vehicle. That is one of the reasons for getting a full size p/u.
Shorties on a truck? Shorties are okay for cars but not on my truck. Long tube Hedman Hedders for a '73 F100 are $120 and readily available anywhere.
 

·
Registered
Joined
·
892 Posts
Yup, the factory Tbird passenger side manifold just touches the frame but clears the engine cradle. Might be able to install without cutting but the bolts would be a pain to install/remove. Also, the exit opening for the manifold sort of points at the frame making it tight. I am tired of having to cram my hands into small places every time I want to work on my vehicle. That is one of the reasons for getting a full size p/u.
Shorties on a truck? Shorties are okay for cars but not on my truck. Long tube Hedman Hedders for a '73 F100 are $120 and readily available anywhere.
As long as you can put up with about 30 seconds of running rich in the 1st two minutes , go for it. My son ran like that for a long time. Not like he had to change plugs or anything. Just smelled rich for a bit. Once they are hot they're fine.
 
1 - 15 of 15 Posts
Top