Reading Spark Plugs - Long Post

Glad you said that, the bottom is much more accessible... That pretty much dictates a position further back on the driver's side, no clearance on the header due to the steering box.
 
How do you read the meter on a dual exhaust? Do you change the O2 sensor from side to side?
 
Ross F-1 said:
Glad you said that, the bottom is much more accessible... That pretty much dictates a position further back on the driver's side, no clearance on the header due to the steering box.
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Here's where I put mine, just one, on the passenger side. Unless you're writing a book, one's all you need.

Mine's about a foot beyond the end of the header.
 

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Thanks Richard! That's a good spot on mine too. I agree, not many things that could make a good-running car be different bank-to-bank.
 
Ross F-1 said:
Thanks Richard! That's a good spot on mine too. I agree, not many things that could make a good-running car be different bank-to-bank.
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Something else to consider: don't leave the sensor in the exhaust pipe all the time unless your A/F meter is in and powered up all the time. Quoting my MTX-L manual: "When installed in the exhaust, the oxygen sensor must be connected and operating with the MTX-L whenever the car is running. An un-powered oxygen sensor will be damaged when exposed to exhaust gas if not properly powered."
 
Ol' Ron said:
Lets take a ride in Richards car. While visiting Richard last year I had the opportunity to observe the the engine i operation from the passenger seat.
Sitting at a stop light waiting for the green the engine was idling at around 14.?? the minute the light changed the car began to accelorate and the AF dropped to around 13.?? as we reached cruise speed the AF began to climb to 16.?? fluxuating between 15.8 to 16.2. Pushing on the loud pedal dropped the AF to 13.??
All this time the timing was going from 20 to 28 degrees.
Having an ignition system capable of providing 40KV is a waste of money because the amt of voltage necessary depends on the resistance between the electrodes of the spark plugs In a Flathead with 8.5CR and plugs gapped at .025 it's doubtful the plug ever sees 10KV.
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Richard in Florida said:

What an amazing memory Ol' Ron has! His numbers are right on the money and he's woven them into a nice clear description of what's happening. Attaboy!
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Well I got my bung installed, and the AFM mounted. I have a few questions on what I'm seeing.

My engine is a mostly stock EAB, heads have not been shaved, bored .060", MSD Ready-to-Run distributor with vacuum advance (limited to 8 deg.), all mech advance is in by 2000-2200 (lightest springs). I have a Rochester 2g off a 283, with #54 main jets, and am running a PCV. I am at 5300'.

At idle,, when I first fired it up with the AFM, I was in the low 10's at idle, and it smelled rich. Played a little with the idle mix screws and popped up into the mid-12's. Not as much smell but I get occasional pops (misses) in each bank (true duals with Red's headers). Not bad, but with it at 10 AFR there is none.

When driving, I get into mid-13's under moderate acceleration.

At a steady 40 mph, about 1750 RPM, flat ground, I barely make it into the high 14's. Any speed change or hill and it's back in the high 13's.

To me, overall the signs are I need to jet down at least one size.

I have to say it's an intriguing piece of technology! I'm amazed how much it jumps around, under steady conditions. Almost makes me wonder if it's the float opening and closing?
 
What you have to do is find the sweet spot in the combination of ignition advance and the AF. With luck this usually only takes a few years.
 
Aw, stealing from the fuel injected crowd:)

A carb will never run like a FI (new one) engine, you'll have to balance it out the best you can.

It was (almost) easier when programming EPROMs. and yes a w wide band O2 sensor is much better for data logging, but not sure if needed otherwise.

A heated O2 may be an option, as a regular O2 sensor needs to get warmed up before god voltage is sent from it...could be why a odd reading is seen when first fired up.

Richard...never heard an O2s sensor could be damage with not volatge applied, could you send the link for your sensor info?...has me curious about a few things.

Thanks.
 
I have the same AFM as Richard, which uses a heated wideband sensor. That's why the instructions say not to operate the engine with the wideband in the pipe but not energized. It will become fouled if the heater isn't running.
 
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