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Author Topic:   Plug Reading Reminder
67Coupster
Gearhead

Posts: 167
From: Fortson, GA, USA
Registered: Oct 2001

posted 10-18-2001 08:06 AM     Click Here to See the Profile for 67Coupster   Click Here to Email 67Coupster     Edit/Delete Message   Reply w/Quote
Alex, how bout that plug reading lesson! Thanks,

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James
67 Coupe
393, AFR 185, 4 Speed, 4.11 9 inch
7.60 @ 94MPH 1/8
1.80 60'(Next Project)

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Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-18-2001 10:22 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
OK, here goes. The tried and true method of reading engine fuel air ratio efficiancy by the color or the plug has all but gone by the wayside. With todays unleaded fuels and or exotic racing blends, the additives play tricks. The key to obtaining the optimum ratio is creating enough heat in the cylinder to burn the fuel and air mixture as efficiantly as possible. One thing that still is a must is to make a full throttle run or WOT blast and kill the engine clean, then coast to a safe stop. You then pull a plug or two (I like to pull numbers 1 and 8)and look very closely at the threads. If they are black and sooty your are very rich and need to lean way out. If there is no color and the plug threads look like new then you are fat or rich. If they are a shiney silver or gray you are in the ball park. The color is about the same as a cigarette ash. Idealy you want to have heat into the second thread, so you should have a shiney silver gray color on the first and half to all of the second thread of the spark plug. If you have silver/gray color into the third thread and beyond you are lean and must adjust the jet accordingly. This method is full proof and will help you optimize your performance regardless of fuel type.

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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stang106
Gearhead

Posts: 707
From: God's Country!... Port Alberni B.C. Canada
Registered: Jul 2001

posted 10-18-2001 12:42 PM     Click Here to See the Profile for stang106   Click Here to Email stang106     Edit/Delete Message   Reply w/Quote
Alex,
Thanks for the lesson, I've printed it and am compiling a binder to refer to. I assume the second time you mention 'rich' you meant 'lean'?
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If there is no color and the plug threads look like new then you are fat or rich.
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A few more plug questions from us rookies!
1)- Why look at the plug after a run of wide open throttle? Is the air/fuel ratio different at other throttle positions?
2)-Start with a new plug?
3)-Is the appearance of the electrode and insulator irrelevant? Wouldn't the threads' appearance be altered by the process of unthreading them out?
4)-Do you clean the threads on the heads really well every time you replace the plug?

Thanks in advance, these questions are probably mundane to most of you, I live in a relatively isolated area that lacks this technical advise.
Dave

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'70 ragtop Stang
"I live my life 16.090 seconds at a time"

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Butch Jennings
Gearhead

Posts: 534
From: California
Registered: Apr 2000

posted 10-18-2001 12:55 PM     Click Here to See the Profile for Butch Jennings   Click Here to Email Butch Jennings     Edit/Delete Message   Reply w/Quote

Alex,

Does this apply to both aluminum and iron heads or does aluminum color the threads different than iron does?

Thanks

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Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.069
Butcher's Home Page
"Friends don't let friends drive Chevys"

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70coupe
Gearhead

Posts: 277
From: Toronto,Ontario,Canada
Registered: Aug 2000

posted 10-18-2001 01:27 PM     Click Here to See the Profile for 70coupe     Edit/Delete Message   Reply w/Quote
In respose to "stang106",the way I read his post is:
He's starting at very rich then going to rich then just right!

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Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-18-2001 01:28 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Dave, a plug that looks like new or has no color on the threads is indeed rich. Not overly, but not lean enough to make optimum power. To answer your questions in the order you asked them 1) at WOT you get full engine temp and "clean" combustion chamber conditions. There is no chance of the cylinder being to cool to get a good reading. Also any soot or other deposits that may have accumulated should blow away. Maximum performance is achieved at WOT and that's the best place to to test at. You can't arrive at "good" dyno figures at part throttle to give you another analogy. 2) A new plug is not required. 3)You are looking at the "inner" portion of the theads and the heat tracks will show up no matter how many times you remove the plugs. the color of the porceline is really irrelevant. The ground electrode should be in tact as if it is too lean then it will dissapear altogether . 4)You don't have to clean the threads at all unless they are really cruddy and then you need new plugs anyway.

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-18-2001 01:35 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
Butch, I first learned of this technique from my alcohol funny car friends Fred Hagen, Brad Anderson and Fred Mandolini. Alcohol does not color spark plugs and they learned early on to use this method. It was then confirmed for me by Don Ward of Autolite several years later. Autolite has a real cool scope that they use to read the plugs "heat" way down inside. In lieu of buing one of these scopes, the thread method works 95% as well. So in answer to your question, it works as well with aluminum heads actually. Aluminum will transfer heat to the plugs beter than iron.

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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Butch Jennings
Gearhead

Posts: 534
From: California
Registered: Apr 2000

posted 10-18-2001 06:32 PM     Click Here to See the Profile for Butch Jennings   Click Here to Email Butch Jennings     Edit/Delete Message   Reply w/Quote

Thanks Alex

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Butch
460 powered 1967 Comet Cyclone
10.271 @ 130.069
Butcher's Home Page
"Friends don't let friends drive Chevys"

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chips67
Gearhead

Posts: 651
From: louisville, ky, usa
Registered: Jul 2001

posted 10-18-2001 10:09 PM     Click Here to See the Profile for chips67   Click Here to Email chips67     Edit/Delete Message   Reply w/Quote
alex, i have read my plugs after a pass and shut down. i was running the last night out and the car was driven to the track...first pass it went 87 mph, quickest mph ever and car was at full temp with 160 stat. the cars mph dropped through the night as the car/air got cooler. i thought its either too lean or too cold. i put in a 180 stat. and jetted up 3 sizes and the car lost 2 mph. the entire ground electrode was silver/gray up to the threads, not into them, BEFORE i went 3 sizes fatter. if what you are sayinG is correct, then why did the car slow down the first time when it was leaner and running cooler? the silver/gray burn wasnt into the threads then....what gives?

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67 coupe, 650dp and rpm intake on 5.0 with afr 165 heads, 4 speed, 4.11's.....best so far is [email protected] in 1/8 mile with 1.79 60ft. time.

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Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-19-2001 01:07 AM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
First of all NEVER EVER make more than one change at a time! Next, put the 160 thermostat back in. Little FoMoCo motors DO NOT like to run HOT! You can lose 2 tenths and 3 MPH with only 20 degrees of temp increase.

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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67Coupster
Gearhead

Posts: 167
From: Fortson, GA, USA
Registered: Oct 2001

posted 10-19-2001 05:41 PM     Click Here to See the Profile for 67Coupster   Click Here to Email 67Coupster     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Moneymaker:
So in answer to your question, it works as well with aluminum heads actually. Aluminum will transfer heat to the plugs beter than iron.


I use anti-seize on the plug threads to keep from galling. Do you see any problems from say not using them on the two plugs I plan to read? The plugs I use are the gasket type if that matters any. Thanks again!

------------------
James
67 Coupe
393, AFR 185, 4 Speed, 4.11 9 inch
7.60 @ 94MPH 1/8
1.80 60'(Next Project)

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Moneymaker
Administrator

Posts: 18704
From: Lyons, IL, USA
Registered: May 99

posted 10-19-2001 09:54 PM     Click Here to See the Profile for Moneymaker   Click Here to Email Moneymaker     Edit/Delete Message   Reply w/Quote
James, you should still be able to read the plug threads with the anti seize. Just wipe it off after you pull the plugs. The heat trace will still transfer.

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Alex Denysenko
Co-Administrator and Moderator
NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00 & '01
Fleet of FoMoCo products
Moneymaker Bio
US Class Nationals link

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