Hotter or colder plugs?

being black means u need to lean it out....but don't lean it out to much without keepin an eye of yur timing. just my 2 cents
 
What engine is this happening in? Is it carb'd? What is the engine set up for? There are several things that could be causing this. How much base timing? Are the plugs looking this way after a bunch of street driving and sitting in traffic idling? Are they looking like this after a WOT pass?

A hotter plug will help keep them clean while street driving.

More base timing will help keep them clean

and as already noted less fuel prior to tip-in.
 
This is a carb'd SBC. Timing is at 38, and FP is around 7.5. Passes are made at WOT then shutdown to get a good reading. The Jeep mainly sees sand drag duty.
 
If its black or white that doesnt affect what heat range you should run. Looking at the strap of the plug there will be a heat index\discoloration on the strap somewhere.

The mark will be short normaly about a 1\8- 1\4" long..

the mark on the strap should be right in the area of the curve where the strap bends from the base to the electrode if its closer to the tip go colder if its close to the base then hotter.. fine tune it with the gap setting..
 
locked timing? I run an NGK FR5 on the street at 38 degrees locked and it ran clean for 3 days of traffic on woodward last year. O2 showed 11.5:1 back then also, now it's in the 14:1 range at idle. FR4 would be hotter. The FR5 didn't like nitrous(porcelin turned orange) so went to an NGK-7.
 
SBC Carb'd??? I wouldnt mess with the heat index at all if your black after WOT run and shutdown. You have a jet issue. Perhaps a look at the power valve if running one is in order also. Most time if your running a good ignition just curving the fuel will do the trick on todays engines,fuels and plug materials.

Also you didnt mention if you were fouling the plugs or not??? Wet?? See if just Black and didnt foul, again its jetting. Drop down 4 numbers square. Try again with new plugs in standard heat range.

Plus you better be a experience plug reader to gather any info most the time anyway. This is basicly for very High HP engines with lots of pop and/or boost( N20) and different fuels(Alky)coming down the hole... in which again most of hot rodders running this type of power have data aquistion on board that tells em everyting anyway without reading plug!

GL....

~Cheese~
 
The Big Cheese said:
SBC Carb'd??? I wouldnt mess with the heat index at all if your black after WOT run and shutdown. You have a jet issue. Perhaps a look at the power valve if running one is in order also. Most time if your running a good ignition just curving the fuel will do the trick on todays engines,fuels and plug materials.

Also you didnt mention if you were fouling the plugs or not??? Wet?? See if just Black and didnt foul, again its jetting. Drop down 4 numbers square. Try again with new plugs in standard heat range.

Plus you better be a experience plug reader to gather any info most the time anyway. This is basicly for very High HP engines with lots of pop and/or boost( N20) and different fuels(Alky)coming down the hole... in which again most of hot rodders running this type of power have data aquistion on board that tells em everyting anyway without reading plug!

GL....

~Cheese~
Click to expand...

That's kind of what I'm hoping to do, is learn more about reading plugs :-)
No fouling plugs. The motor made just under 700HP N/A, so it makes a little power, and the carb is a Pro Systems dominator, so I hate to screw with it. But, I can get some different jets and take them with us this weekend.
igotaneed4speed, thanks for the info and the links, and thanks everybody for any other info.
 
Changing main jets is not screwing with it..Thats Hot rodding.. Fuel/air mix has to be right to make the numbers. or you can burn one down or not compete!!! Then thats cost you 12k or a lost event.

I remember back in 1991 at US Nats Indy we were running S/G then I changed jets on two 750's(900cfm a piece) 8 jets 5 times and went down 3 numbers once and up 10 numbers by the end of the day 4 more times. It was 81' 90% hum with 29.7 baro to start the day 7.30 am then the day ended with 67' 30% 30.4 baro 6pm.:hitfan:

When you start playing with the carb cam timing/duration of shot, metering or air bleeds, polishing , booster change now your messing with the carb. Most should be done on the bench first for baseline ref numbers then applied to engine per volumetric efficiency http://www.installuniversity.com/install_university/installu_articles/volumetric_efficiency/ve_computation_9.012000.htm.


Knock er down 4 numbers square bet you be close...

GL..

~Cheese~

ps. if your not fouling or wet and their black sooty then your not too cold..and or if you dont see the shiny specs your not too hot... your close. Again..Plug reading isnt what its cracked up to be these days because of what I had mentioned before. Only to the pro classes mostly where every 1/1000 sec and 2 mph means packing it up on the trailer.
 
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502SS said:
That's kind of what I'm hoping to do, is learn more about reading plugs :-)
No fouling plugs. The motor made just under 700HP N/A, so it makes a little power, and the carb is a Pro Systems dominator, so I hate to screw with it. But, I can get some different jets and take them with us this weekend.
igotaneed4speed, thanks for the info and the links, and thanks everybody for any other info.
Click to expand...


Call Patrick.
 
yep, mayube he set it up for drag and not cruising around? Square jetting and no power valve screwed my idle and cruise up[ so I went back with Pat's specs with a powervalve up front and all is well again. I tried no PV just for fun but it runs the same ET with and without..goodluck!@
 
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