Spark Plug Analysis

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Coors

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Re: Spark Plug Analysis

Look again; feed is #2 high; #4 low;#6 low;#8 high.
#1low; #3high;#5 high;#7low


Standing in front of the engine;

look at the above.

high means one side of plenum; l
ow means other side of plenum

Each bank gets 2 high plenum feed, and 2 low plenum feed.

I see the point trying to be given, but that dual plane is real forgiving, unless you have an issue so bad that you could smell it.
 
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Coors

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Re: Spark Plug Analysis

Reel Poor said:
Coors, are you arguing what I highlighted in RCS post? If so, he is correct. What you have posted is simply the sparkplug arrangement on each side of the engine.
Click to expand...

How can you people see my edited/deletes?
 
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Coors

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Re: Spark Plug Analysis

Reel Poor said:
Coors, are you arguing what I highlighted in RCS post? If so, he is correct. What you have posted is simply the sparkplug arrangement on each side of the engine.
Click to expand...

I'm about to give up trying to explain it.
 
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Coors

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Re: Spark Plug Analysis

RCSConstruction said:
Still debating I see???
Bond-o nailed it.
One side is too lean/rich.
Take a look at a manifold. Starboard side of plenum feeds 3-5-2-8
Port side feeds 1-7-4-6.
Click to expand...

What is your point? the manifold is not single plane, one side feeding one bank.
 
Last edited:
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Loren Warner

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Re: Spark Plug Analysis

Guess what I'm getting from this is to probably look at my idle mixture adjustments again.
 
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RCSConstruction

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Re: Spark Plug Analysis

Bottom line here..

8 P light / 7 S dark
6 S dark / 5 P light
4 S dark / 3 P light
2 P light /1 S dark
Fwd

This shows us that ONE side of the dual plane manifold is feeding the cylinders too much/too little air/fuel.
If he lugs his boat around then I bet the starboard side of carburetor is running rich, if he hotrods it then maybe an air leak or a lean condition on the port side of carburetor.
Bank order,firing order does not mean anything. Look above, The starboard sides are rich the Port sides are lean.
 
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RCSConstruction

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Re: Spark Plug Analysis

RCSConstruction said:
Bottom line here..

8 P light / 7 S dark
6 S dark / 5 P light
4 S dark / 3 P light
2 P light /1 S dark
Fwd

This shows us that ONE side of the dual plane manifold is feeding the cylinders too much/too little air/fuel.
If he lugs his boat around then I bet the starboard side of carburetor is running rich, if he hotrods it then maybe an air leak or a lean condition on the port side of carburetor.
Bank order,firing order does not mean anything. Look above, The starboard sides are rich the Port sides are lean.
Click to expand...


Also wanted to add that as mentioned above you could have the wrong size "jets", although the weber (AFB/Edelbrock/carter/) use metering rods. Would be very easy to get a mix matched set installed by a big "re-builder" because they don't build one carb at a time, many parts are exchanged/interchanged.
If they are all the same you might have a vacum leak on that one side. maybe the carb base gasket, intake manifold? That side isn't getting the same "pulse" or "draw" as the other.
Is the "light" a light brown color or a ash white? Is the dark a oily black or a caramel brown?
This should steer you in the right direction.
 
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Coors

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Re: Spark Plug Analysis

Maybe I'm not a good explainer.
Reel, good to see you back in here.

The numbers ain't firing order, they are the cylinder #'s One bank, 1357; other 2468 Standing in front of the engine-
The dual plane sends one side of the carb, primary and secondary, to 2 cylinders on each bank; the other side, primary and secondary, sends gas to the other 2 cylinders on each bank, dammit.Standing in front of engine, right hand is 1357, left is 2468 cylinder order, from front to aft.
a dual plane mixes up the charge, so one side problem of a carb won't show up on one bank; only a single plane would do that. sigh
 
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Coors

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Re: Spark Plug Analysis

RCSConstruction said:
Also wanted to add that as mentioned above you could have the wrong size "jets", although the weber (AFB/Edelbrock/carter/) use metering rods. Would be very easy to get a mix matched set installed by a big "re-builder" because they don't build one carb at a time, many parts are exchanged/interchanged.
If they are all the same you might have a vacum leak on that one side. maybe the carb base gasket, intake manifold? That side isn't getting the same "pulse" or "draw" as the other.
Is the "light" a light brown color or a ash white? Is the dark a oily black or a caramel brown?
This should steer you in the right direction.
Click to expand...

I think you are right; the lower tubes in the manifold are too rich,one side of
carb), or the normal vacuum leak.
Good call.
 
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Coors

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Re: Spark Plug Analysis

I need to relax from work, and go back to the basics- dual plane on a 1970 340 duster, shortened 4.88 spool,Alston 4 link, Strange 33 spline axles.
The older you get, the more you forget.
good call, rsc
 
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RCSConstruction

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Re: Spark Plug Analysis

Coors said:
I need to relax from work, and go back to the basics- dual plane on a 1970 340 duster, shortened 4.88 spool,Alston 4 link, Strange 33 spline axles.
The older you get, the more you forget.
good call, rsc
Click to expand...


haha, Been a long week that's fer sure.:cool:
 
Bondo

Bondo

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Re: Spark Plug Analysis

I stand corrected, sir
Click to expand...

Ayuh,...... No harm, No foul, Coors,......


Btw,....... My Dad was Sir,......... I'm just plain ole Bondo..........:D
 
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Loren Warner

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Re: Spark Plug Analysis

It's a brand new carb, not rebuild. Think I'll run it and squirt wd40 around gaskets to see if any change and change gasket if anything noted. Will also take another look at the mixture settings. Then after getting a good run will pull plugs 1 and 2 and go from there. It'll probably be another week or two before I'm able to launch the boat and will give you results of my findings. Thank you all for taking the time to offer advice.
 
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Coors

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Re: Spark Plug Analysis

Yeah, if it idles ok, the idle screws aren't the problem, and if they where, the plugs should self clean under a load. Run wot, then look at plugs (don't let it idle long, or false reading).
 
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