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-   -   Spark plug interpretation (http://forums.pelicanparts.com/porsche-911-technical-forum/222524-spark-plug-interpretation.html)

Christien 05-21-2005 07:36 AM

Spark plug interpretation
 
I just pulled my plugs, and would appreciate some assistance in interpretation, as this is my first time, and I don't really trust my own interpretation. Sorry if they're not #'d right, I don't know the correct ordering, so I just numbered them 1-6, starting from left top down, then right top down :
1 4
2 5
3 6

From comparing them to the pic in the Haynes manual, Im thinking I may have some oil deposits on 2, 3, 4 and 6. 1 and 5 look pretty good. On the blacker ones, there doesn't look to be any sludge or oily crap, they're just black (looks more like carbon or soot).

Thanks for any help!
Chris

http://forums.pelicanparts.com/uploa...1116689712.jpg

Christien 05-21-2005 07:48 AM

Also forgot to mention that according to 101 Projects, I'm hoping it might just be regular deposits from gas. ("modern gasoline formulations sometimes can make the spark plugs black or sooty, even when the car is running properly"). I also suspect my mixture is rich.

They're Champions, and I'll be replacing them with Bosch.

Wil Ferch 05-21-2005 08:11 AM

They Haynes manual ( I believe) still gives you info as if the plugs came from a pre-emissions controlled car. They never ( I believe) updated the pictures.

The plug pics shown by Haynes will not match a "modern" ( post 1970, say) car. Today's plugs will look toward white / grey and be OK.

Wil

Wil Ferch 05-21-2005 08:54 AM

Oops...just saw you have a 72....maybe there is a meanigful "reading" you can take on these plugs.

I'll take a first crack....fairly OK with some small oil control problem on the motor..looks somewhat oil soaked / fouled...but hard to read over the internet. Doesn't seem serious.

Others?

Wil

Christien 05-21-2005 09:14 AM

Thanks Wil.

If it makes any difference, my Haynes shows the first publication year as 1977, or at least that's the first copyright year in there. A bit more info: I've got Zenith carbs, and I probably had some extra gas blow through there at one point - I unknowingly hooked an MFI fuel pump up when changing the original leaky one, which, with its 25psi gas flow, blew gas right through the cylinders and out the bottom of the engine, with no combustion occuring.

Just finished putting the new plugs in. Didn't notice any difference at idle, but I haven't yet taken it out for a drive to see if there's any difference. Heh, at least it starts properly :D

randywebb 05-21-2005 09:43 AM

post a pic of the electrodes (end on) & state what your '72 T has - MFI?

BTW, this is too rich:

http://forums.pelicanparts.com/uploa...1116697239.jpg

Christien 05-21-2005 09:49 AM

Sorry if this a retarded question, but what are the electrodes? The end of the plug wires? I can't tell from the pic you posted.

I've got Zenith carbs.

Thanks,
Chris


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