Topic: Read this spark plug

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This is an NGK V-Power TR55 with one 14-hour race on it.  The rest of the porcelain is bright white with tiny black specks.  The v-groove NGK cuts into the copper electrode is still sharp and looks new.  I did a little research on reading spark plugs, but nothing I found could explain the big black spot.  It's not soft carbon--I tried to clean it off after taking the picture and it's burned onto the plug.  Engine seemed to be running fine.

Former chief proprietor and lead bad idea generator of Binford "More Power" Racing, 2010-2013: humbly self-proclaimed the best Chevy Beretta in Lemons history.

Re: Read this spark plug

Generally speaking I would drop a couple heat ranges if you had no overheating to have caused the specks.

Is this a pre raced engine?

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Re: Read this spark plug

If that has a 14 hour race on it you are running very slightly lean.  You should have a little carbon on the plug. 

The black mark is likely where the fuel/air mixture is entering the cylinder and hitting that spot on the plug.  That's the spot that is looking at the intake valve.  It's hot and the fuel hit that spot and tars or carbons up before the plug sparks.  It's not something I would worry about since the rest of the plug looks fine.

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4 (edited by obsolete 2012-04-01 10:22 PM)

Re: Read this spark plug

Team Infinniti wrote:

Generally speaking I would drop a couple heat ranges if you had no overheating to have caused the specks.

RobL wrote:

If that has a 14 hour race on it you are running very slightly lean.  You should have a little carbon on the plug.

I was thinking of going a step colder to TR6s.  There are also the TR5s, which are the same heat range as the TR55, but a smaller gap (.040" instead of .060").  The TR6s also .040" out of the box.

Team Infinniti wrote:

Is this a pre raced engine?

First race on this engine.  143k on the street before that...

RobL wrote:

The black mark is likely where the fuel/air mixture is entering the cylinder and hitting that spot on the plug.

Thanks, that's kind of what I was thinking, although I suspected it might be oil from the PCV or something.

Former chief proprietor and lead bad idea generator of Binford "More Power" Racing, 2010-2013: humbly self-proclaimed the best Chevy Beretta in Lemons history.

Re: Read this spark plug

Reduce the gap of a good running engine? Not what I do.
I sorta suspected, the spots are likely 143k of crud stirring, no biggie.

Drop a range and explore a slightly richer mixture per RobL but remember the newer fuels are not leaving the same readings we were using back in the day.

How was the temp?

Homestead Chump 5th-Sebring 6th-PBIR Lemons 9th - Charlotte Chump  CrashnBurn 9th
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6 (edited by obsolete 2012-04-01 10:23 PM)

Re: Read this spark plug

Yeah, the intake manifold has some PCV and EGR garbage in it.  Not really caked on, but it's there.  I can see how that might end up as little black dots on the plugs.  I thought our temps on track were great, we never got over 190-195F.  Also, we have been running 89 octane, always E10.

The step-colder TR6s come gapped at .035", vs. our stock gap of .060".  I could try pulling them out to .050 or so, but I think .060" might be a little extreme coming from .035".

EDIT: TR6s come gapped at .040" according to NGK's site.  I had read .035" on a forum somewhere, but that's wrong.

Former chief proprietor and lead bad idea generator of Binford "More Power" Racing, 2010-2013: humbly self-proclaimed the best Chevy Beretta in Lemons history.

Re: Read this spark plug

Dont push it too much.

Homestead Chump 5th-Sebring 6th-PBIR Lemons 9th - Charlotte Chump  CrashnBurn 9th
Sebring 6th again -NOLA Chump 1st -PBIR Chump Trans Fail 16th
Daytona 11th - Sebring 6th - Atlanta Motor Speedway 2nd - Road Atlanta Trans Fail 61st-Road Atlanta 5th
Daytona 13th - Charlotte 9th - Sebring 2nd-Charlotte 25th broken brakes - Road Atlanta 14 10th-Daytona 14  58th- Humid TT 19th Judges' Choice!