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I'm adding an O2 sensor and AFR gauge to my '78 F100, and I'm not sure where to install the sensor - things are tight up by the headers. I see an area downstream from the collector (Option A) or about 2 feet further downstream from that (Option B). Any suggestions? Thanks!
Usually in or near collector is best. Too far downstream it may not read accurately since it won't get hot enough. The instructions with the gauge should indicate a range of distance from cylinder head they recommend placing the sensor.
Location B is way too far away from the collector. I’m not thrilled with location A either. Get it as close as possible. Looks like there might be some room to get it closer if you weld the bung on the driver’s side.
Usually in or near collector is best. Too far downstream it may not read accurately since it won't get hot enough. The instructions with the gauge should indicate a range of distance from cylinder head they recommend placing the sensor.
Yes paperwork should say where to place it but with headers it gets a little harder.
Originally Posted by Viper Pilot
Location B is way too far away from the collector. I’m not thrilled with location A either. Get it as close as possible. Looks like there might be some room to get it closer if you weld the bung on the driver’s side.
They say the collector is not a good place as it dose not get the "mixture" from all the cylinders and why it should go a short distance after the flange but not at B.
Do you have more room on the other side?
Guess I am lucky I have a 300 six running EFI manifolds and they have a hole for the factory O2 and where I put mine.
Dave -----
Thanks everyone! The documentation just says, “If long tube headers are used, the oxygen sensor should be installed in the collector. If cast iron manifold(s) or shorty headers are used, install the sensor in the pipe just below the manifold.”
These are long tube headers, but the collector is short. It’s a typical Bosch sensor and an AutoMeter Pro-Comp Ultra-Lite gauge. I think right downstream of the flange would work. I’m planning to use a clamp-on bung since I don’t have access to a welder locally. That stainless looks way better than the rusted steel!
…and the passenger side is about the same - maybe a litter tighter to the transmission pan.
Being the collector is short and think about the same on most you need all 4 tube to blend before they get to the O2 sensor but not too far that it dose not get heated.
If it dose not say it also needs to be placed at the top or 45* from there. If placed at the bottom besides maybe getting knocked off on high ground water / condensation will also hurt it.
I run a AEM 30 - 4110 AFR gauge in my 81 F100 flare side with a 300 six and it showed me the carb the truck came with was junk and the Ebay one was way too lean.
Good luck with the install and tuning
Dave ----
Thanks, Dave. I finally bit the bullet and bought a new distributor - one with vacuum advance. I plan to install the sensor and gauge this weekend and check my baseline. Then I'll go back to start and install the distributor, set the timing, check the curve, and then move on to the carb. I've done almost everything on this truck out of order!
Thanks, Dave. I finally bit the bullet and bought a new distributor - one with vacuum advance. I plan to install the sensor and gauge this weekend and check my baseline. Then I'll go back to start and install the distributor, set the timing, check the curve, and then move on to the carb. I've done almost everything on this truck out of order!
Some times it is not how we got there as long as we do get there
If it makes you feel better I had a miss when under power, showed up when I was pulling a 20 ft enclosed trailer.
I though advance so pulled vacuum NG, then carb so changed it as it was all over the scale and was a mess when I got the truck and had one on the shelf NG.
Did a few other things and the last was to pull plugs as I did not think they were all that old or miles. When I pulled #3 I found the miss, plug was fouled but compression was good.
Checking over records I had 28K on the plugs So I should have pulled the plugs first and saved a lot of time & work.
For me it was "I got there"
Dave ----
Some times it is not how we got there as long as we do get there
Very true! I got the sensor and gauge installed and did a few other minor things to the truck. I was running super rich at idle, although I hadn't tuned the carb for summer temps this year. I made some basic adjustments, and things seem to be running better. The new distributor arrived, so I didn't want to waste too much time tuning the carb until I install the distributor and set the timing. After that, I'll go back to tuning the carb and probably undo some of the band-aid "fixes" I made earlier.
The AFR gauge sure does provide a lot of information! I wish I installed one earlier.
I installed the distributor. The first distributor arrived with a damaged vacuum can. I installed the replacement. The vacuum advance is supposed to only provide 10-degrees, but it's providing 15-degrees of advance. I don't know if that changes anything for me, but I reached out to MSD for feedback.
While at it, I checked resistance in my wires, and it wasn't pretty! Some had really high resistance. Others showed no continuity. Not sure what to make of that - the engine wasn't running too poorly. I ordered a new set of wires and some heat boot covers.
Lastly - I did a compression test. All cylinders seem fine considering the age of the engine (low of 130; the rest at 139-140).
I would say once you have good plug wires installed and base timing set to where you want it take it for a drive and see how it goes.
It has been over 10 years since I had a MSD distributor and that was in my drag car so did not have vacuum hooked up so dont remember if there was a way to limit vacuum advance or not?
Mechanical IIRC had plastic bushings that went over the weight stops and you also got a bunch of springs to adjust how fast the weights moved, I had the lightest springs for drag racing.
Dont know if the bushings could be used for vacuum or not?
Is the vacuum can adjustable with a Allen thru the vacuum port?
The factory distributor on my 300 six can be adjusted but it only adjusts at what HG the advance starts to move / work not a total limit.
I would say if total timing is too much then use the bushings on the mechanical weights and let the vacuum do it's thing.
Dave ----
I've found the MSD vacuum advance units to run as high as 20 degrees. All you need is 10 for a performance stand point. I've used a screw/nut in the slot to limit it or a threaded hole with screw and shaved washer. Use thread lock.
So I should have pulled the plugs first and saved a lot of time & work.