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Old 12-03-2004, 07:38 AM
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O2 sensor bung placement/ manifold choice

Hi Guys:
I am putting a 454 in an 88 chevy k1500 pickup. The present engine is a 350. The doner vehicle is a 1987 R30 one ton chevy truck. I am going to use standard headers with 2 cats and siamesed duels and retain the 1987 TBI fuel injection. My question is which is better for O2 placement, on a single tube on the left header like I have seen some headers with the bung welded on from the factory, or lower on the collector? Also, does anybody know if you can use a 4 bbl aftermarket manifold under the 454 throttle body? The throttle body has 2 big barrels but under the main body there is an adapter (stock) that opens into a standard Q-jet spread bore pattern. I have to retain EGR to cut down on ping (this setup has no knock sensor) and keep the check engine light off. I know Edelbrock makes a manifold for this setup but its a little pricey ($250). i was hoping to find a used manifold for under a $100. Any help would be app.

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Old 12-03-2004, 11:33 AM
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As close to the exhaust port as possible is what the manufacturers of the Sensors (Bosch etc.) will tell you, that being said you have to decide if you want the sensor in one exhaust port stream or all of one bank at the collector. Some people place the sensor directly in the exhaust stream just slightly downstream of the port in the leanest cylinder, this will take some experimentation to find out which cylinder is the leanest.

A collector location means the sensor take longer to warm up and in extremely cold climates (like Canada) you may need to insulate it and the header to get accurate results. A shorty header makes this a non issue, mount it in the collector...it will be close enough.
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Old 12-03-2004, 01:07 PM
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O2 senser

Where are the sensers located on the stock exhaust manifolds?
I would attempt to locate the O2 senser as close to the stock location.
If the bung is 2 inches from the exhaust port of # 4 cylinder, then that is where I would drill the hole for the bung.
If its 18 inches from the exhaust flange, thats where I would go. Get the idea?

From what I have been told over the years, #1 and 8 cylinders tend to run leaner than the rest, on Chevy engines.
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Old 12-03-2004, 01:12 PM
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Idealy you would run the oxygen sensor from the center of the x piping to get overall readings. Second to that I would set it in the collector so at least your getting readings for 1 bank. For warmup issues you can just run a heated oxygen sensor that uses a 12v power source to heat itself up.
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Old 12-03-2004, 01:15 PM
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O2 senser

Other than placing the senser as close to the origional stock location as possible, what do the instructions say that came with the senser? Presuming this is not a Stock senser.
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Old 12-03-2004, 05:07 PM
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The stock oxygen sensor was located on the back of the left manifold a few inches above the manifold/pipe connection. So it saw (or smelled?) all four cylinders on that side. I do not have an aftermarket sensor with directions. I planed to use the stock sensor. The question is which is better? Test one cylinder at a hotter tempature or all four farther away from the head which would run cooler. The use of a heated O2 would help with the lower bung connection. Maybe I should weld 2 bungs in while its still apart so I can try it both ways if necessary? What do you guys think?
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Old 12-03-2004, 05:35 PM
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A heated sensor will not solve a cold location, it only assists with the warmup.

Go to Bosch for more information.
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Old 12-03-2004, 06:14 PM
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http://minimopar.knizefamily.net/ecu/oxygen_se.html
http://www.msdignition.com/fuel_12.htm :Scroll down to the oxygen sensor.

While it does assist with warmup it also helps control the heat of the sensor keeping it within operating temperatures.
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Old 12-03-2004, 08:31 PM
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O2 sensor

I am thinking if you were to use center dump shorty headers, if they will fit your vehicle, to put the O2 sensor at the top of the collector would be about as close as you could get to the stock location, comparatively. At least there it could sence all 4 cylinders fairly equally.

Another option and probably the least desireable is to run the stock exhaust manifolds.

Summit has the center dump shorty headers for the BBC, Hookers, part # HOK-2180, for the painted version.

Last edited by Max Keith; 12-03-2004 at 08:28 PM.
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Old 12-04-2004, 06:02 AM
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You have to put it close enough to stay warm, but it does not have to be that close to the engine. Just find a place in the collector to the headers and you will be fine. The sensor does not have to be that hot to operate. There is no need to put it in a single tube of the header. The temp is not that much different there than in the collector. I would be willing to bet that it would be just fine in a properly placed X or H pipe, but could possibly give you some problem at idle placed there if it is not a heated sensor.

Chris
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Old 12-19-2004, 09:08 AM
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Hi Guys:
The headers I had would not fit because they were for a 1987 chevy truck (454) and i am installing that engine in a 1988 k1500. I bought a set of hookers off ebay new for $125 and they have a bung already installed in #7 tube down low almost to the collector. I figure hooker knows the best place to put the bung as they could have put it anywhere but chose that position. THANKS FOR EVERYONES INPUT!
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Old 12-19-2004, 11:40 AM
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You may have to wrap your headers to keep the check light off.

I put Edelbrock tubular manifolds on my 94 K1500 350. After runing down the highway, when I'd slow down to turn a corner, the headers would cool off, and trip the light. Around the corner, and back on it, the light would go out.
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Old 12-19-2004, 12:31 PM
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Just use a heated sensor if your worried about that. I wouldn't wrap any part of my exhaust if I could help it. The moisture that builds up between the wrap and the exhaust slowly begins to rust the metal.
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