One Spark Plug looks lean

flyingd

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Sep 18, 2011
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I have a 1969 starchief V with the 4 cylinder 120 hp in it. Serial number on a plate, 2647628.

The number 3 cylinder spark plug looks like it is running lean. Number 1& 2 look fairly normal, 3 looks lean and 4 looks almost fairly normal.

What do you think will cause this.
 

Don s 2

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Aug 29, 2012
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Re: One Spark Plug looks lean

Do a compression test. Low compression will keep the cylinder from sucking in the fuel.
 

Bondo

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Re: One Spark Plug looks lean

Ayuh,.... Water will clean sparkplugs, brand new clean, but you say it looks lean,....
 

flyingd

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Re: One Spark Plug looks lean

The electrode that you bend for the gap looked white. It was the only one looking like that. They are brand new ones too.

Just curious, does one barrel of the carb feed two cylinders and the other barrel feed the other two??
 

Don S

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Re: One Spark Plug looks lean

Just curious, does one barrel of the carb feed two cylinders and the other barrel feed the other two??

Nope, do the compression test. That will tell the story.
 

flyingd

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Re: One Spark Plug looks lean

I will have to do the compression test. Thanks for the help.


One other thought; are the valves hydraulic or solid?
 

Bondo

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Re: One Spark Plug looks lean

I will have to do the compression test. Thanks for the help.


One other thought; are the valves hydraulic or solid?

Ayuh,.... Hydraulic,...
 

flyingd

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Re: One Spark Plug looks lean

forgot to ask.........what should the compression be, besides even that is
 

Bondo

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Re: One Spark Plug looks lean

forgot to ask.........what should the compression be, besides even that is

Ayuh,.... Generally speakin',...

100/ 110 is a rebuildable core motor....

120 to 130 is a Tired motor,....

Over that, is a Healthy motor,....
 

flyingd

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Re: One Spark Plug looks lean

Thanks, that is very helpful.

I will be doing the compression test next week and will let you know what happens
 

flyingd

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Sep 18, 2011
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Re: One Spark Plug looks lean

Ok I did the compression test after letting the engine warm up in the sun. I wiil give 2 numbers, 1st will be normal comp test and the 2nd will be with oil squirted in the cylinder.
1- 115, 130.
2- 112, 125.
3- 105, 125.
4- 115, 125.

Those are the numbers. Tell me what you think.

Thanks.
 

Bondo

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Re: One Spark Plug looks lean

Ok I did the compression test after letting the engine warm up in the sun. I wiil give 2 numbers, 1st will be normal comp test and the 2nd will be with oil squirted in the cylinder.
1- 115, 130.
2- 112, 125.
3- 105, 125.
4- 115, 125.

Those are the numbers. Tell me what you think.

Thanks.

Ayuh,.... She's Tired,.... A rebuildable Core motor...
 

flyingd

Seaman
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Sep 18, 2011
Messages
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Re: One Spark Plug looks lean

I was afraid of that.

Where would I find a long block................or the parts to do the overhaul myself.
 
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