Indexing a spark plug

I've heard that before "methanol burns slower than gasoline" but I always ran my McCullough's with the absolute lowest timing advance I could get. Why the contradiction, I did very well with 91s, 101's and reed opens. Even with my Komt K78, I ran much less timing than most. Of course you didn't use alcohol in that one.
 
I know with nitrous on our drag car we run 3 degrees colder plug. nitrous when it ignies is hot like alky...gas is not as hot of a charge when it ignites like alky."alky fires hotter " that's why you get more power than gas"so if you want more btu's for power why run 11 degrees colder plug with gas? gas calls for a w16 fsu I've been told run the w27fsu....I might be wrong idk I know alot of you guys know these 4 strokes.im just asking because I'm trying to learn what works best.

How Do I Find a Colder or Hotter Plug?
NGK indicates the heat range in the middle of the plug number. For example, BCPR6ES-11 has a heat range of 6. (The number after the “-“ is the gap.)
Starting with part # BKR6E-11 (heat range 6), a colder plug would # BKR7E-11 (heat range 7), a hotter plug would be # BKR5E-11 (heat range 5).

EXCEPTION: NGK Racing Plugs: (Any NGK plug that begins with the letter “R”)
For NGK Racing Plugs, the heat range is located AFTER the hyphen.
Example: R5671A-10 has a heat range of 10. A colder plug would be # R5671A-11 (heat range 11), a hotter plug would be # R5671A-9 (heat range 9).
Some NGK Racing Plugs are also available in half heat ranges. These are displayed as a 2 or 3 digit number after the hyphen. For example, R6120-85 has a 8.5 heat range and R6120-105 has a 10.5 heat range.
 
every plug is different
denso calls for w16fsu for gas
and people us w27fsu for alky. as the number goes up it gets colder.autolite 458 gas hot 411 cold number goes down..

ex.goggle w16fsu cross reference and it will give you cross-reference for other manufators there part #.you can use this with any plug to find out what you use
 
^ or just run the W24FS-U and be done with it.
hot < 16 - 22 - 24 - 27 - 31 > cold

If you're concerned about fouling the plug or it getting sooted up from an over-rich condition, open the plug gap to .040" - just make sure you have enough voltage at the end of the plug wire (ie hot coil.) If you're insistent on using the 16 plug, really watch your engine temp.

We've won many races back in the day using the same 24 heat range plug racing on gas one night and alcohol the next. No changes other than jet.
 
^ or just run the W24FS-U and be done with it.
hot < 16 - 22 - 24 - 27 - 31 > cold

If you're concerned about fouling the plug or it getting sooted up from an over-rich condition, open the plug gap to .040" - just make sure you have enough voltage at the end of the plug wire (ie hot coil.) If you're insistent on using the 16 plug, really watch your engine temp.

We've won many races back in the day using the same 24 heat range plug racing on gas one night and alcohol the next. No changes other than jet.

that was my question with running gas was the W16fsu a little to hot if not using stock carb set up and would going to a w20 or w24 lower the temps and not hurt but help power wise..
 
Each plug range will drop the cylinder head temp 10-15*F. So, realistically, going from the 16 to a 24 could drop the cylinder head temps by 30-45*.
Rule of thumb: The more modifications and compression the engine has (ie cylinder pressure,) the colder the plug you will want to use.
 
I agree with that, but on the other part of your answer, have you ever tried dyno testing this idea using an EGT?

Yes, Al. If the engine is tuned correctly, the heat range of the spark plug didn't make much (if any) difference on the dyno. For extended runs on the track, however, the hotter heat range plugs continued to build cylinder head temp, whereas the colder plugs leveled off sooner. Again, the compression is so extremely low in these engines (about 6 - 6.5:1) that I don't think you'll see much going on there in the short time they're under load on the dyno. We, instead, manipulate the on-track temperature of the engine with the plug heat range (right or wrong.)

I've discussed on here before how we throw a bunch of ignition timing advance to our restrictor plate engines, dump tons of fuel to it, then try to light it with a hot plug (and still have to tape the fan shroud completely off to build any cylinder head temp at all.) The egt. runs between 8-900*F to make peak power on these small plate flathead engines. If we tune them to an "optimum" egt, it flat kills the power on them. It's an anomaly that we deal with on almost a daily basis with these small plate flathead engines. I certainly have my own theories and conjecture about the "why," but data and experience back up what's occurring. That's good enough for me to accept it and move on.
 
Plug heat range is mostly about the plug then anything else. Carbs operate under lots of different variables, rpms, throttle openings, and environmental (air density for instance, right AL?) and it is impossible to get the mixture perfect under all conditions. The plug needs to dissipate enough heat so the plug does not melt or cause detonation. It needs to be hot enough so it does not foul. In terms of tuning exhaust temp. is far more valuable then head temp. I have never observed ceramic boil on a stock class flatty.
 
Yes, Al. If the engine is tuned correctly, the heat range of the spark plug didn't make much (if any) difference on the dyno. For extended runs on the track, however, the hotter heat range plugs continued to build cylinder head temp, whereas the colder plugs leveled off sooner. Again, the compression is so extremely low in these engines (about 6 - 6.5:1) that I don't think you'll see much going on there in the short time they're under load on the dyno. We, instead, manipulate the on-track temperature of the engine with the plug heat range (right or wrong.)

I've discussed on here before how we throw a bunch of ignition timing advance to our restrictor plate engines, dump tons of fuel to it, then try to light it with a hot plug (and still have to tape the fan shroud completely off to build any cylinder head temp at all.) The egt. runs between 8-900*F to make peak power on these small plate flathead engines. If we tune them to an "optimum" egt, it flat kills the power on them. It's an anomaly that we deal with on almost a daily basis with these small plate flathead engines. I certainly have my own theories and conjecture about the "why," but data and experience back up what's occurring. That's good enough for me to accept it and move on.
I always hypothesized that the inconsistencies were caused by fuel puddling at the front of the plate. Never tried it but wondered if it would not be better, in terms of ease of tuning, to restrict flow at the air horn rather then at the intake port.
 
^ Many years ago, Mike Clements made a reducer (not legal btw) for the flathead carb counterbore that tapered down to the different carb restrictor plate sizes. This eliminated the fuel puddling problem that does exist. However, the tune on the engine was basically the same -- dump tons of fuel to it. I still have several of these that I acquired in a buy-out of Clements Racing if anyone has a use for them.
 
^ Many years ago, Mike Clements made a reducer (not legal btw) for the flathead carb counterbore that tapered down to the different carb restrictor plate sizes. This eliminated the fuel puddling problem that does exist. However, the tune on the engine was basically the same -- dump tons of fuel to it. I still have several of these that I acquired in a buy-out of Clements Racing if anyone has a use for them.

What about reducing the compression ratio? Has anybody tested that idea?
 
I haven't specifically tried that since the rules don't allow machining of the combustion chamber at all, it would be difficult to gain much (legally.) We've found that having more piston pop-up (+.005" max per rules) is advantageous over having the piston in the deck @ TDC.
Further, angle decking the block helps unshroud the valves, which helps flow considerably.
 
not too sure flow doesn't beat compression every time... one of the best engines I ever had/have the piston was in the hole by .010 and the head was cut just enough to ensure the surface was flat... deck was angled and the timing was a "real" 26 degrees.. it had the first of a combination cam I ended up running a lot.. 7X intake and a 96-3 exhaust profile... darn thing won a couple of state championships and finished 3 in the` nationals for a friend one year. won a lot of other races..finally just wore it out and re-sleeved it with the exact same angle it had originally.. frankly was scared to change a thing...not the best carb on the flow bench but was the best for that engine(clue there).. you just never know sometimes...
 
not too sure flow doesn't beat compression every time... one of the best engines I ever had/have the piston was in the hole by .010 and the head was cut just enough to ensure the surface was flat... deck was angled and the timing was a "real" 26 degrees.. it had the first of a combination cam I ended up running a lot.. 7X intake and a 96-3 exhaust profile... darn thing won a couple of state championships and finished 3 in the` nationals for a friend one year. won a lot of other races..finally just wore it out and re-sleeved it with the exact same angle it had originally.. frankly was scared to change a thing...not the best carb on the flow bench but was the best for that engine(clue there).. you just never know sometimes...


I agree, Jimmy - we concentrate on flow over compression on these flatehad engines by far. Piston pop-up always helps though -- just not as much as flow does. The flow with the piston popped out of the deck <=.005" @TDC for a millisecond doesn't hurt the flow at all. I suspect that if you took your winning engine and angle cut the deck further for max pop-up (thus unshrouding the valves even more) you'd make a bit more power yet.
I'm like you though, when something works and is proven, it's difficult to make changes to it. :)
 
EXCEPTION: NGK Racing Plugs: (Any NGK plug that begins with the letter “R”)
For NGK Racing Plugs, the heat range is located AFTER the hyphen.
Example: R5671A-10 has a heat range of 10. A colder plug would be # R5671A-11 (heat range 11), a hotter plug would be # R5671A-9 (heat range 9).
Some NGK Racing Plugs are also available in half heat ranges. These are displayed as a 2 or 3 digit number after the hyphen. For example, R6120-85 has a 8.5 heat range and R6120-105 has a 10.5 heat range.

the NGK R plug goes the opposite direction of all others . The 11 is the coldest and the 7 is the hottest. Low number hot/High number cold
 
Run the same 411 plug (or my preference, an ND W24FS-U) for either gas or alcohol and you'll be fine. You can run a slightly hotter plug on gas if you like, but there is no need to if it is fueled correctly.

I prefer to index my plugs so that the ground strap opening is facing the middle head bolt on the right side of the cylinder head. You can also point it toward the exhaust valve if you like. There is a reason that I do it the way I do, but the important factor is that the intake valve cannot hit the ground strap of the plug.

We stock the indexing washers if you need. Just give us a call at the shop number as we are still open and still able to ship for now.

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Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
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31 years of service to the karting industry
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
So what is the other reason for doing it?
 
Al,

I believe that the amount of power an engine can produce is based on the *delta* in temperature in the combustion chamber between the fresh charge and the amount of heat/energy produced in combustion, as well as the total BTUs created from combustion. It's not an absolute temperature thing. Methanol can show a lower EGT number than gasoline, yet still produce more power/work.
HP or work done is a direct relationship with delta T
 
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