AFR Question - Team Camaro Tech
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post #1 of 14 (permalink) Old Dec 15th, 19, 07:55 PM Thread Starter
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AFR Question

What can cause one bank of the engine to read 2-3 points different than the other? I notice at idle my D/S reads 14 and my P/S reads 11. The passenger side seems to be rich by a couple of points pretty much throughout the range, although it is kinda hard to determine it as the numbers are changing all the time. Can a carburetor adjustment effect this reading? I am a little stumped. The only thing that is unique between the banks are valves and rings, right?

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post #2 of 14 (permalink) Old Dec 15th, 19, 08:18 PM
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Re: AFR Question

Exhaust gasket leak?

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post #3 of 14 (permalink) Old Dec 15th, 19, 08:42 PM Thread Starter
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Re: AFR Question

Quote:
Originally Posted by dyno jonn View Post
Exhaust gasket leak?
I do hear a tick when I'm accelerating on the passenger side. Does sound like a exhaust leak, yes. Would that run lean or rich?

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post #4 of 14 (permalink) Old Dec 16th, 19, 04:09 AM
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Re: AFR Question

An exhaust leak would cause a lean reading with your AFR.

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post #5 of 14 (permalink) Old Dec 16th, 19, 05:11 AM
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Re: AFR Question

what type of intake are you running? a dual plane intake can show differences from side to side
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post #6 of 14 (permalink) Old Dec 16th, 19, 12:29 PM
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Quote:
Originally Posted by bhodgdon400 View Post
what type of intake are you running? a dual plane intake can show differences from side to side

Ahhhh, good info. I will check when I get home. I don’t recall although I do know it’s aluminum.
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post #7 of 14 (permalink) Old Dec 16th, 19, 05:56 PM Thread Starter
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Re: AFR Question

Yes, it is an air gap dual plane intake manifold.

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post #8 of 14 (permalink) Old Dec 16th, 19, 06:35 PM
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Re: AFR Question

Quote:
Originally Posted by bhodgdon400 View Post
what type of intake are you running? a dual plane intake can show differences from side to side

A dual plane splits every other cylinder in the firing order.... so no, that is not the cause.

Does is stay the same throughout the RPM range?

First swap your sensors side for side & see if the rich/lean sides switch.

Fix your exhaust leak... this is a major cause of mixture problems, especially at idle.

Also verify where your PCV valve and or power brakes are connected. It allows extra air to that cylinder if directed to one port. At the carb base it should not cause a problem.
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post #9 of 14 (permalink) Old Dec 17th, 19, 02:01 AM Thread Starter
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Re: AFR Question

Quote:
Originally Posted by Lonnie P View Post
A dual plane splits every other cylinder in the firing order.... so no, that is not the cause.

Does is stay the same throughout the RPM range?

First swap your sensors side for side & see if the rich/lean sides switch.

Fix your exhaust leak... this is a major cause of mixture problems, especially at idle.

Also verify where your PCV valve and or power brakes are connected. It allows extra air to that cylinder if directed to one port. At the carb base it should not cause a problem.
I do not have a PCV connected to vacuum at this point. My power brakes are pulling vacuum from the rear manifold vacuum port. I actually have a vacuum gauge connected from the rear carb base.

I think I can monitor the AFR while pushing on the brakes and see if it changes. I will focus on the exhaust leak to determine if in fact there is one and just exactly where it is.

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post #10 of 14 (permalink) Old Dec 17th, 19, 06:49 PM
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Re: AFR Question

Disconnect & plug the vac line to see if it makes a difference.
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post #11 of 14 (permalink) Old Dec 19th, 19, 12:12 AM
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Re: AFR Question

Cam timing or exhaust leak is the usual suspect. 11.xx at idle is really rich though. That's richer than WOT should be unless your boosted, lol
How do the plugs look?
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post #12 of 14 (permalink) Old Dec 19th, 19, 04:16 AM Thread Starter
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Re: AFR Question

Quote:
Originally Posted by Dash808 View Post
Cam timing or exhaust leak is the usual suspect. 11.xx at idle is really rich though. That's richer than WOT should be unless your boosted, lol
How do the plugs look?
I degreed the cam, so it should be good. Since one bank is at 14, the other at 11 is concerning me. I tried to check timing last weekend and my timing light quit on me, but I discovered why I could not get a consistent reading on my timing light before it crapped out. I have a Summit multi spark captivate ignition box. My timing light was not multi-spark light. I ordered one from Summit and it should arrive today.

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post #13 of 14 (permalink) Old Dec 19th, 19, 06:22 AM
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Re: AFR Question

Check the plugs on the rich side. A bad plug or wire causing a misfire would make AFR rich.
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post #14 of 14 (permalink) Old Dec 19th, 19, 06:23 AM
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Re: AFR Question

An article testing Edelbrock's Pro-Flo-4 EFI in January 2020 Hot Rod reads in opening paragraphs the test mule is a carbureted 454 having 3-point difference AFR.

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