Plug Reading for Power

I finally registered so I can post. Belated thanks to all those who posted earlier on the article. I can tell you I've learned so much more, especially the midwest posse, from all than I can repay. Great thing about Buick lovers, willing to share. Also congrats to all GSE competitors, you've sure got those cars flying!

This is an article one of the SS racers shared. It's food for thought and I can attest that "most" people run the car too rich for max power! I use this religiously with good quality race gas in my cars. Also do not store race gas in your gas tank, it only "lasts" a matter of hours when vented. Don't mix brands either!.

Plugs are best viewed with 10x power illuminated magnifying glass.

Heat range= Ground Strap, the ground strap indicates the heat range of the spark plug. If the "color" of the ground strap "changes" too close to the ground strap's end(which is above center electrode), then the heat range is "too cold", meaning that the strap is losing heat too quickly to the base ring, and is not able to burn off deposits until near it's end. If the "color" of the strap changes near where it attaches to the base ring(last threaded ring), then it means that the plug range is "too hot", because heat is not transferred/cooled from the strap to the base ring quickly enough!! The strap might begin to act like a "glow plug", eventually causing preignition or detonation. Proper heat range is when the "color" is at the halfway point on the strap, neither too cold or too hot.

(Color= meaning the evidence of heat/or lack of heat by the appearance of dark vs. lightened color of metal.)

Jetting= the air/fuel mixture ratio shows up on the base ring(the last threaded ring, it has strap welded to it). You want a full turn of light-soot color on the base ring!! If you want to turn for max power, then you want 3/4 to 7/8 ths of a full turn of light soot color to turn up on base ring. This is on ragged edge of too lean,but makes max power. To be safe leave a full turn. If the base ring has a full-turn of color, but there are "spots" of heavy build-up of "dry soot" on top of color, then jetting is too rich.

Note: If the base ring has a full turn of color with some spots of heavy dry-soot, then jetting is too rich, REGARDLESS, if porcelian may be "BONE-WHITE", jetting is TOO RICH!!! Do not look at the porcelian to read jetting!!!

Porcelian= the porcelian shows up preignition/detonation, it will not accurately reveal jetting/air-fuel ratios. To look for the first signs of detonation, search the white porcelian for tiny black specs or shiny specks of aluminum that have fused to the porcelian.

When detonation occurs, part of air fuel mixture explodes instead of burning, the explosion heard as a "metallic knock", this audible knock is the result of a shock wave, this shock wave travels back and forth across the clearance volume "disrupting" the cooler boundary layer gases that cover the entire area, this disruption allows more "heat" to be transferred into parts, especially piston domes!!! TROUBLE! With the early signs of detonation, the shock wave will also rattle rings causing the tiny amount of oil that now gets by the rings, to be fused to the white porcelian as tiny black specks. One step beyond the black specks will be tiny specks of aluminum coming off the piston tops. Then the porcelian cracks and etc.

Center electrode= the very tiny sharply defined porcelian ditch that encircles the center electrode, will also show early signs of preignition, detonation or wrong heat range. Look for signs of the ditch being filled with melted porcelian, you need a 10x magnifying glass.

The "ground strap"=Heat Range
The "plug's base-ring"=Jetting
The "porcelian"=sogns of preignition/detonation

Thanks to Meaux Racing-MaxRace Software!

Tom Rix
Top Stock Buick 5433

 

Great topic Tom,Thanks
Now I have even more to look at and try next time at the track.

 

Thanks Tom. Your helpful tips are always appreciated.:TU:

 

Tom, THANK YOU!

Now I've found out that what I was taught was wrong, and what I've been doing was all wrong. Now to go back and check my plugs in my bike and car...

 

BIG GIANT THUMBS UP!!! Tom

Rest assured that a copy of this will go in my tool chest, be hung in the shop (in a few different spots:grin: ), in each car's glove box (just in case:Brow: ) and have a few spares to boot!:TU:

Welcome aboard.

 

Thanks.

Thanks guys. I should clarify that this is max power at strip with proper fuel and engine temp. Should also work on street but I would always be a little on the "rich" side for safety.
Race fast and safe!
Tom

 

Tom,
Black specks on the porcelain means too much timing correct?

 

Great info, Tom.
What temp do you like for exhaust temp on a pass. I see between 1350 and 1410.

Bruce

BQUICK
JAGUICK

 

This is like the oldest thread known to mankind..



Jeff I see you found the search button :TU: ..

this is good info and should be a sticky

 

Jeff, usually the issue is too much timing but not enough octane or jet can also contribute. Really need to understand burn rate of fuel and specific gravity to set proper timing as some fuels burn (accelerate the car) quicker than others.
As specific gravities are different for various brands of fuel you need to change jets to compensate. If one fuel you are using has a specific gravity of .710 and another one that you want to try has .730 you will need to reduce jetting by about 3% to compare power levels. (.710 divided by .730 = 97.2%).

Bruce, I like to see 1300-1350 degrees (12.9-1) with Top Stocker and 1400-1425 with Super Stocker (10.4-1). Also remember when you find the range that works in your car it is dependent on ambient air temps. If 1350 degrees is the magic number on a 50 degree day then you need to shoot for 1390 degrees on a 90 degree day as you need to either add or subtract the ambient air temp differences.

Tom

 

Anything posted by Tom should be sticky.

Thanks Tom