Spark plug heat range/carbon buildup

S

Sedanman

Well-known member
I should be picking up my head with a fresh mill of .050 and broken exh bolts removed tomorrow and start working on re-assembly. I was quite surprised to see that my cylinders had so much carbon in them when the plugs are so clean/white, which I'd assumed was due to the bad exhaust manifold leak. How can the plugs be so clean, but the combustion chambers (and exhaust ports/manifold) so coated in carbon?

http://www.flickr.com/photos/sedanman/3 ... otostream/

I've got 45 plugs in there now, and the shop the did the compression test suggested I go down one heat range. If I'm milling the head too, I assume that should be two heat ranges, but am concerned about plugging up my freshly cleaned engine with carbon in short order...
 
I would just try one heat range. Run about a hundred miles and look at the plugs. Also it may be your style of driving or you may need to do some adjusting on the carb. Almost sounds like you are not driving far enough to warm up properly to burn off all the carbon. Depending on your type of normal driving, you may have to ocasionsally take it out and make a long run to get the accumulated carbon out or once in a while you may have to do an upper cylinder cleaning.

Fred
 
Looking up inside the plug ends, you've got carbon soot on the plugs as well - just the ends are clean.

From what I've gathered, 45 plugs are the hottest ones Motorcraft makes - apparently Ford Sixes have extremely cold-running chambers.

If you find a hotter plug let me know what it is.
 
The guy who did the leakdown test was concerned that these were TOO hot a plug; I think you guys are right about driving style, though, as I've been taking it easy on the car with the horrible exhaust manifold leaks as I was concerned about burning valves after seeing the plugs looking like this many miles ago. I'm not sure how my rich/lean new Pony Carbs 1100 will run along with the head mill of .050, so will probably go down just one range like you are suggesting and see what happens. With the exhaust leak gone I'll be doing more spirited driving for sure :nod:
 
I've been trying to find colder plugs today (and a cork trans gasket - not available anywhere) and a bit confused; The person I just spoke to at NAPA said a 46 Autolite is colder than a 45 - is this correct? I thought it was the other way around as I used to run 44's in my 170. Nobody seems to have anything other than a 46...

If I have to go to another brand of plugs, brands and heat range suggestions are appreciated; I'm running 45's now and they are too hot (see link to photo above)
 
Thanks - an interesting article. But it doesn't really answer my question: Is a higher number hotter, or colder? Three auto parts stores seem unsure...
 
From my notes;
"...AC, ACCEL, Autolite, Bosch, and Champion use lower numbers for colder plugs, while NGK and Denso use higher numbers for colder heat ranges."

Here's the Autolite numbering system; http://www.autolite.com/pdf/SparkPlugNu ... System.pdf

A chart showing Autolite plug heat range chart; http://www.cvproducts.com/upfiles/Autolite.pdf

And a Champion plug heat range chart; http://www.cvproducts.com/upfiles/Champion.pdf

For the life of me, I don't know why plug manufacturers seemingly keep their heat-range info a secret, or at least hard to find)
 
Thanks, jamyers, but my frickin' windows 2000 won't open the pdf files. I got the 46 Autolites, so I'm hoping they are colder than the 45's...
 
what can I say - my computer's on it's last leg and will hopefully last till Windows 7 comes out. As for the plugs...
 
If you aren't having any pinging just stick with the 45's. Spark plugs need to run hot enough to keep the crud burned off to prevent fouling, but not so hot as to cause detonation. Basically the hotter the better until it's too hot. Clear as mud, eh? But you didn't mention ANY indication that would lead me to believe that a colder plug was needed other than the recommendation from someone who never saw the engine run.
Joe
 
Sedanman":1od32121 said:
Thanks, jamyers, but my frickin' windows 2000 won't open the pdf files. I got the 46 Autolites, so I'm hoping they are colder than the 45's...
Click to expand...
Other way around - an Autolite 46 is a hotter plug than a 45.
 
Are you sure its not valve seals? Oil will crud up the cylinders pretty fast even though you are dead on with your mixture/timing.

Ron
 
I don't think so; No smoke or oil usage that I've noticed, and the last oil was in there for well over 3000 miles :oops:

Trying again - is a 46 hotter or colder than a 45? :roll:
 
46 is the next hotter ploug after 45. See: http://www.autolite.com/pdf/SparkPlugNumberingSystem.pdf

Looking at last two numbers of a 2545 plug:

1. EVEN (first) number designates a Resistor/Suppressor plug. For Non-Resistor plug types, subtract 10.
2. ODD number designates a Non-Resistor plug. For Resistor plug types, add 10. Indicates heat range within a plug family:
2544 - Next coldest plug in this family.
2545 - Medium heat range plug in this family.
2546 - Next hottest plug in this family.
Click to expand...

45 is a resistor plug
44 is colder
46 is hotter

A hotter or colder plug will not correct improper (rich/lean) mixture, which leads to carbon buildup or piston/valve burning.
 
Thanks, guys. So that means NAPA was wrong - I think 46 was the lowest number they had. So if I need to go colder, how do I reference this to a different brand with a different set of numbers?

This project is becoming way more complicated than I'd planned - local paint store gave me the wrong color of POR 15 Ford blue, so had to order it and won't have it for another week. I'll be lucky to have this thing on the road again by the time the rains come ... :(
 
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