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  Lesson #4 reading spark plugs

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Author Topic:   Lesson #4 reading spark plugs
Moneymaker
Administrator

Posts: 29200
From: Lyons, IL, USA
Registered: May 99

posted 04-21-2002 12:57 PM     Click Here to See the Profile for Moneymaker        Reply w/Quote
Well, I have been telling you guys about looking at the threads on spark plugs for what seems to be eons now.
During our tests there were some well know dirt track racers there having their motors dynoed along with ours. While testing VP C-11 vs C-12 we took plug readings to see the differance.
After a few pulls, we removed some plugs and the other racers remarked how lean we had the engine due to the color of the plug porcelain. They were near white.
In fact, we were dead fat. We barely got the first thread on the BF-12's. We leaned it out another step and picked it up 7-8 HP on the C-11 (which we already knew).
The plugs stayed white, but we got an ash color into the second plug thread.
The dirt guys were amazed to say the least.
The problem lies in the additives used in all of the racing fuels. They do not leave any deposits on the porcelain as the BTU's are so high. Alcohol is even worse.
Read your threads.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link

kid vishus
Gearhead

Posts: 7251
From: middle of NC
Registered: Oct 2000

posted 04-21-2002 01:18 PM     Click Here to See the Profile for kid vishus        Reply w/Quote
quote:
Originally posted by Moneymaker:
They do not leave any deposits on the porcelain as the BTU's are so high. Alcohol is even worse.


When I pull my plugs all I see is an ugly brown colour on the porcelain from the top lube. And since I was kinda rushed for time to get the car ready, I put the plugs out of last years motor in, so the threads were already "colored" up.

Guess I need to buy some new plugs.

chips67
Gearhead

Posts: 663
From: louisville, ky, usa
Registered: Jul 2001

posted 04-21-2002 04:36 PM     Click Here to See the Profile for chips67        Reply w/Quote
thats great information, but what if you are driving a car that runs 87-92 octane? also, am i wasting my time running higher octane on a motor that will run on 87 with less timing?

------------------
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.

chips67
Gearhead

Posts: 663
From: louisville, ky, usa
Registered: Jul 2001

posted 04-21-2002 04:42 PM     Click Here to See the Profile for chips67        Reply w/Quote
im running 9.5:1 compression with 58cc aluminum heads. i usually run 93 chevron, used to run amoco ultimate. how can i read my plugs? also, would using an egt sensor at the header primaries be more accurate?

------------------
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.

capri man
Gearhead

Posts: 8777
From: doerun, ga.
Registered: Nov 2000

posted 04-21-2002 07:43 PM     Click Here to See the Profile for capri man        Reply w/Quote
my plugs actually look a little lean like you said. porcelin is almost white with maybe a little tinge of brown. but the threads are black smutty. am i to rich?? thanks

------------------
mike r
racing is real
everything else is just a game.
81 capri-7.56 @88mph 1/8
1.56 60 ft.
http://prestage.com/site/site_display.asp?SiteID=141

R&J MOTORSPORTS
Journeyman

Posts: 94
From: Tampa,Fl.
Registered: Aug 2000

posted 04-21-2002 07:59 PM     Click Here to See the Profile for R&J MOTORSPORTS        Reply w/Quote
Alex, so is the C-11 good for 7-8 hp.with the same set up? (plugs,timming,jetting,etc.)I bought some C-11 but haven't tried it yet. Thanx, Joe

------------------
Joe Strunk
NHRA SS/MA 2890
1964 SS/MA Comet
1965 PRO-Street Fairlane
1966 Fairlane Conv.

John Kolhei
Journeyman

Posts: 46
From: Cottonwood,mn,usa
Registered: Feb 2002

posted 04-21-2002 09:37 PM     Click Here to See the Profile for John Kolhei        Reply w/Quote
I fell asleep in class; where can I read about reading plug threads?

jsracingbbf
unregistered
posted 04-22-2002 02:37 AM              Reply w/Quote
Alex, Question, to properly read plugs don't you have to shut down at the END of the track BEFORE you drive back to the pits? the reading would be off some from the return road ride. IF you pull them after each pass. I used to pull plugs, I now use an EGT, which I built myself. If you buy a K type thermocoupling from a electrical supply house and a Temp/ Milli volt convertor from Fluke ( both less than a Ben Franklin ) hook them up to your DVM and set it on Min/ Max record and make a pass. When you get back you will have a highest EGT for that cylinder. All for less than $120.00 bucks

Jerry

V8 Thumper
Gearhead

Posts: 4777
From: Phoenix, Arizona
Registered: Dec 2001

posted 04-22-2002 08:13 AM     Click Here to See the Profile for V8 Thumper        Reply w/Quote
quote:
Originally posted by jsracingbbf:
...All for less than $120.00 bucks


Sounds like a slick little setup. Not to be a smart a**, but wouldn't you need to make at least 4 or 5 passes to validate a particular reading, using only one EGT reading at a time? (assuming you're clamping to the primaries, right?)

[This message has been edited by V8 Thumper (edited 04-22-2002).]

Moneymaker
Administrator

Posts: 29200
From: Lyons, IL, USA
Registered: May 99

posted 04-22-2002 10:37 AM     Click Here to See the Profile for Moneymaker        Reply w/Quote
Best way to take a plug reading is to shut down after WOT. Our Percy's EGT meter has a memory that records the highest reading.
Joe,C-11 is worth 3 to 8 over C-12 depending on the engine and operating range. Usually you need to go up ONE jet size with an Autolite 4100.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link

R&J MOTORSPORTS
Journeyman

Posts: 94
From: Tampa,Fl.
Registered: Aug 2000

posted 04-22-2002 08:43 PM     Click Here to See the Profile for R&J MOTORSPORTS        Reply w/Quote
Thanx,Alex. I'll give it a try. I was thinking on the dyno first, for an equal comparison. I just see 8400 rpm. not the big #'s you are use too.

------------------
Joe Strunk
NHRA SS/MA 2890
1964 SS/MA Comet
1965 PRO-Street Fairlane
1966 Fairlane Conv.

kid vishus
Gearhead

Posts: 7251
From: middle of NC
Registered: Oct 2000

posted 04-22-2002 08:53 PM     Click Here to See the Profile for kid vishus        Reply w/Quote
quote:
Originally posted by R&J MOTORSPORTS:
I just see 8400 rpm.

Sheesh

Dusty Kiser
Gearhead

Posts: 191
From: Bethel,Oh USA
Registered: Mar 2002

posted 04-22-2002 10:02 PM     Click Here to See the Profile for Dusty Kiser        Reply w/Quote
quote:
Originally posted by jsracingbbf:
Alex, Question, to properly read plugs don't you have to shut down at the END of the track BEFORE you drive back to the pits? the reading would be off some from the return road ride. IF you pull them after each pass. I used to pull plugs, I now use an EGT, which I built myself. If you buy a K type thermocoupling from a electrical supply house and a Temp/ Milli volt convertor from Fluke ( both less than a Ben Franklin ) hook them up to your DVM and set it on Min/ Max record and make a pass. When you get back you will have a highest EGT for that cylinder. All for less than $120.00 bucks

Jerry



I'm curious, what kind of numbers you guys are seeing on your EGT's. The EGT's we use require drilling a hole in the primary as close to the piston as possible, and the end of the probe as near the center of the tube as possible. I've seen the temps low from being too rich AND low from being too lean , usually accompanied by a nice little hole in the piston from detonation. I still read plugs because they tell a lot more than just temps. For example oil dilution, aluminum throw off, etc. But, old habits die hard.

jsracingbbf
unregistered
posted 04-22-2002 11:12 PM              Reply w/Quote
Dusty, I still look at the plugs for oil and foreign material, but not as much as I used to for jetting. I run mine in the number 1 exhaust tube about 1-2 inches down the tube from the head. I welded 1/8th inch pipe bungs to each tube, so I can change cylinders. I generally see approx. 1100 to 1200 deg. F when it's set up right. Preferably 1180 and I use the time slip to back this up. I record the EGT on each timeslip then enter it into the Family software log book on the laptop. After a few recordings you begin to see a trend where the car likes the EGT to be for best ET. Also I have seen as you mentioned the temp go real high for a lean condition up to a point then go back real low. But it drops off sharply and it's obvious on my car because it is missing badly. I'm no expert by any means I just record what I see and go from there.

jsracingbbf
unregistered
posted 04-22-2002 11:18 PM              Reply w/Quote
I forgot to mention for mr v8 thumper, I only run One EGT, 8 would be nice, but I run it in the leanest cylinder, or at least what I THINK is the leanest cylinder. I tune all 8 for this reading. No problems car runs great like this. Alcohol is a very forgiving fuel. If I had to though I could fine tune each cylinder by doing as you mentioned, moving it to other cylinders. Sorry for all the posts.
Thanks
Jerry

Moneymaker
Administrator

Posts: 29200
From: Lyons, IL, USA
Registered: May 99

posted 04-23-2002 10:07 AM     Click Here to See the Profile for Moneymaker        Reply w/Quote
Close to 1500 degrees Dusty.

------------------
Alex Denysenko
Co-Administrator and Moderator/ non 65-66 Mustang owner sensitivity co-ordinator

NHRA/IHRA/SRA member
NHRA and IHRA SS/LA National Record Holder '00, '01, & '02
Fleet of FoMoCo products including 88 ASC McLaren Mustang #28
Part time secret agent license #0089
US Class Nationals link

chips67
Gearhead

Posts: 663
From: louisville, ky, usa
Registered: Jul 2001

posted 04-23-2002 10:08 PM     Click Here to See the Profile for chips67        Reply w/Quote
alex, what about my question? what exactly am i wanting to see on the threads with pump gas on my motor? will the threads on a plug for aluminum head extend into the chamber enough to get a reading?

------------------
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.

Stang85
Journeyman

Posts: 43
From: Virginia Beach, Va. USA
Registered: Mar 2001

posted 04-24-2002 12:13 PM     Click Here to See the Profile for Stang85        Reply w/Quote
One major factor in obtaining accurate egt readings is when the reading is taken. People on this thread are correct in reading plugs after shutting off at WOT going through the lights. In a similar fashion, you need to have an egt gauge that allows you to lock and hold the reading at WOT through the lights. If you allow the egt to continue running and only record the highest reading experienced on the run, you will not have the correct numbers. Why? Because as you lift off the throttle after clearing the traps, the sudden closing of the throttle will cause an immediate lean condition resulting in the egt reading to go higher. This is the reading you will see on the guage back in the pits rather than what the engine was experiencing at WOT.

Dusty Kiser
Gearhead

Posts: 191
From: Bethel,Oh USA
Registered: Mar 2002

posted 04-26-2002 11:00 PM     Click Here to See the Profile for Dusty Kiser        Reply w/Quote
quote:
Originally posted by Moneymaker:
Close to 1500 degrees Dusty.



Whew! ARE you using thermal barrier coatings on your cumbustion surfaces? Obviously, your running awesome but, do the peek power settings ( jetting, timing, EGT's etc. ) stand up on the track as the quickest? Our experience suggests that for hard accelleration the fuel wants to be a little fat. Do SS class rules still prohibit porting heads other than slight port matching and seat blend? I'm amazed you can turn that many RPM's. You've obviously found something I've never seen. Judging from your records damned few others have either! I'm a fan!

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