Hi Guys,
I just finished changing the plugs on the monaro cause they were fouled. I know this is due to my Carby so that's not the question.
I was sitting there gapping the plugs and wondering.. What does it matter!?
I know that too large of a gap and you wont get a spark... but what about too small? Ive heard theories about the spark not being big enough to ignite the mix etc... What is the thruth!?
Also plug heat ranges... I'm currently running BP7FS plugs in the monaro and since putting the 850 carb on theyve been fouled badly and quickly. I was thinking about putting some BP6FS plugs in to try and burn the fouling away so that they dont get gunked up so easily. Is this the right thing to do? How else with it affect the engine? Is it likely to cause pre-detonation?
Just curious.. I kinda have SOME knowledge on this.. just wanted to hear other's opinions and knowledge!
Thanks!
Heat Range of sparkplug and Gapping
Started by
_Tiny_
, Jan 04 2006 01:22 PM
23 replies to this topic
#1
Tiny
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Posted 04 January 2006 - 01:22 PM
#2
_LX406_
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Posted 04 January 2006 - 02:04 PM
I found about 20Hp by changing the heat range of the plugs on my 400 on the engine dyno.
#3
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Posted 04 January 2006 - 02:22 PM
You went hotter or cooler?
I was recommended to run hotter plugs on the street to help keep the fouling down, but change to cooler plugs to race on so as not to ping.
Cheers for the reply! and thats alot of HP to gain just from a $20 set of plugs!
I was recommended to run hotter plugs on the street to help keep the fouling down, but change to cooler plugs to race on so as not to ping.
Cheers for the reply! and thats alot of HP to gain just from a $20 set of plugs!
#4
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Posted 04 January 2006 - 04:42 PM
Isnt standard for holdens for in NGK(what you are using) a 5 rating?(I know your Monaro is anything but Standard Tiny)
7 is a very cold plug, and would easily be prone to fouling if not racing etc.
Too big a gap, can obviously cause probs, and so can too small. If youve got at least a 1mm gap then that isnt going to be the cause of missfires/fouling or anything sinister and the car should run fine, but depending on the extra coil voltage available youll get better performance by going larger, how large, dont know, possibly a bit of trial and error in your application Tiny.
7 is a very cold plug, and would easily be prone to fouling if not racing etc.
Too big a gap, can obviously cause probs, and so can too small. If youve got at least a 1mm gap then that isnt going to be the cause of missfires/fouling or anything sinister and the car should run fine, but depending on the extra coil voltage available youll get better performance by going larger, how large, dont know, possibly a bit of trial and error in your application Tiny.
#5
_Yella SLuR_
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Posted 04 January 2006 - 05:45 PM
BP's are Bosch plugs, their numbers go up for hotter plugs. NGK go down in their numbers for hotter plugs.
Just give it a go Tiny and see what happens, your numbers are only going to be better or worse!!!
Just give it a go Tiny and see what happens, your numbers are only going to be better or worse!!!
#6
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Posted 04 January 2006 - 07:08 PM
BP are NGK plugs, i only use NGK if i can get them and Champion if i cant ( never needed to use champion plugs yet though!)
I was told that NGKs the higher the number the COLDER they are.
I belive that your correct Devils, 5's are the "standard" heat range.
When we built my engine we began with 6s ( to minimise heat and pinging in the new engine), and switched to 7s when the carby was being a bit cantankerous before we realised how stuffed it was! By chaning to 7s, the temperature guage dropped around 10 degrees farenheight and the car didnt really feel very different
I'm thinking about going back to 6s to see what it does now that its run in and just guage what happens. Just that repco only had 2 6s! (Not much good in an 8 cylinder i told the lady!)
Anyway THanks for the advise, If anyone else has more ideas/comments throw em in!
Cheers!
I was told that NGKs the higher the number the COLDER they are.
I belive that your correct Devils, 5's are the "standard" heat range.
When we built my engine we began with 6s ( to minimise heat and pinging in the new engine), and switched to 7s when the carby was being a bit cantankerous before we realised how stuffed it was! By chaning to 7s, the temperature guage dropped around 10 degrees farenheight and the car didnt really feel very different
I'm thinking about going back to 6s to see what it does now that its run in and just guage what happens. Just that repco only had 2 6s! (Not much good in an 8 cylinder i told the lady!)
Anyway THanks for the advise, If anyone else has more ideas/comments throw em in!
Cheers!
#7
_Dirty Deeds_
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Posted 04 January 2006 - 07:33 PM
Tiny, with NGK, the higher the number, the colder the plug.
Im running NGK "7" plugs and I found them Ok on BP Ultimate but when I ran a few tanks of Shell Optimax, they started to foul up. Ran the 8's for drag racing and they were too cold. The engine builder advised me to stay clear of the 6's. My 308 is standard stroke and making 390HP, nothing big.
What fuel are you running?
NGK also make a "V" Groove plug ( in 7's and 8's ) which are supposed to be even better than the standard. You cant buy them off the shelf, only by special order. Let me know if you want me to track down the part / plug number.
Cheers
Im running NGK "7" plugs and I found them Ok on BP Ultimate but when I ran a few tanks of Shell Optimax, they started to foul up. Ran the 8's for drag racing and they were too cold. The engine builder advised me to stay clear of the 6's. My 308 is standard stroke and making 390HP, nothing big.
What fuel are you running?
NGK also make a "V" Groove plug ( in 7's and 8's ) which are supposed to be even better than the standard. You cant buy them off the shelf, only by special order. Let me know if you want me to track down the part / plug number.
Cheers
#8
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Posted 04 January 2006 - 08:56 PM
Is there anything inherently wrong with the 6's? or just your engine builder thought they werent cool enough for your application?The engine builder advised me to stay clear of the 6's.
#9
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Posted 04 January 2006 - 09:29 PM
Deeds: thanks for the reply...
That never occured to me! I'm currently on a tank of bloosy optimax shit... and thats when its foulded up badly... i usually use ultimate but theyve been out!!
Hurm! might have to go for a LOOONG drive and get rid of the crap in the tank. and fill up with ultimate.
THough i do remeber that it did begin to foul the plugs even with ultimate ( my carb IS mega rich on the primaries/idle circuit)
Same question as Devils.. why not the 6s?
Cheers mate!
That never occured to me! I'm currently on a tank of bloosy optimax shit... and thats when its foulded up badly... i usually use ultimate but theyve been out!!
Hurm! might have to go for a LOOONG drive and get rid of the crap in the tank. and fill up with ultimate.
THough i do remeber that it did begin to foul the plugs even with ultimate ( my carb IS mega rich on the primaries/idle circuit)
Same question as Devils.. why not the 6s?
Cheers mate!
#10
_Dirty Deeds_
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Posted 04 January 2006 - 11:44 PM
Yeah spot on, he didn't think the 6's were cold enough.
Never tried it with 6's.
Never tried it with 6's.
#11
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Posted 05 January 2006 - 12:23 AM
Interesting topic Tiny, I am following this one with great interest now. In my 383 Chev, I have also been running NGK "7"s, ever since I've had this motor (these were what my engine builder said to run). I know 5's are standard, 6's are 1 colder, so these 7's are 2 heat-ranges colder. Some of my mates said there's no need and I should run 6's, and that you would only need to go to 7's if you start making around 500HP (which I'm no where near), but I'm sure my engine builder had good reasons for running 7's.
I always run Mobil Synergy 8000 Premium Unleaded, and generally speaking have never had any troubles. On a couple of occasions in the earlier days, I did have some fouling problems, but I believe this was more due to carby probs. The rest of the time it's been perfect. However I have often wondered if there would be any benefit for me to go back to 6's, especially since I spend 90% of my time just cruising around the streets. Could this make the fuel burn any better in this situation?
What about gaps? What do you run Tiny? And everyone else?? I set mine to around 0.030" (HEI ignition), can I go higher?? Once again, my engine builder always said I should stay around 0.028" - 0.030", however the guy I bought my ignition system from (ICE), said I could go bigger to 0.035" or more. Who do I listen to? The ignition guy is an expert on ignitions, but the engine builder is an expert on engine behaviour and runs hot cars up on dyno's all day long.......
I always run Mobil Synergy 8000 Premium Unleaded, and generally speaking have never had any troubles. On a couple of occasions in the earlier days, I did have some fouling problems, but I believe this was more due to carby probs. The rest of the time it's been perfect. However I have often wondered if there would be any benefit for me to go back to 6's, especially since I spend 90% of my time just cruising around the streets. Could this make the fuel burn any better in this situation?
What about gaps? What do you run Tiny? And everyone else?? I set mine to around 0.030" (HEI ignition), can I go higher?? Once again, my engine builder always said I should stay around 0.028" - 0.030", however the guy I bought my ignition system from (ICE), said I could go bigger to 0.035" or more. Who do I listen to? The ignition guy is an expert on ignitions, but the engine builder is an expert on engine behaviour and runs hot cars up on dyno's all day long.......
#12
_Dirty Deeds_
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Posted 05 January 2006 - 12:48 AM
My engine runs a Crane unit and we gap the plugs @ 0.028".
I hear what you are saying about the 6's ( 90% cruising ) but I prefer the 7's so that if I wanna go ( 50% of the time ), the plugs are going to play their part. Sure, they may foul up from time to time, but that's the nature of the game.
Mine aren't too bad, and I will guess that most of us will experience a foul set of plugs from time to time, but they're relatively cheap and pretty easy to change.
I will stick with the 7's.
I hear what you are saying about the 6's ( 90% cruising ) but I prefer the 7's so that if I wanna go ( 50% of the time ), the plugs are going to play their part. Sure, they may foul up from time to time, but that's the nature of the game.
Mine aren't too bad, and I will guess that most of us will experience a foul set of plugs from time to time, but they're relatively cheap and pretty easy to change.
I will stick with the 7's.
#13
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Posted 05 January 2006 - 06:53 AM
I use "6"s set at .035" on the road & change to "7"s set at .028">.030" for the track.
lxchev listen to the ICE people they know there ign. systems.
lxchev listen to the ICE people they know there ign. systems.
#14
_Yella SLuR_
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Posted 05 January 2006 - 09:39 AM
My err. Point I was making just be aware that some plugs go up for hotter, others go down in their numbers for hotter.
#15
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Posted 05 January 2006 - 04:55 PM
Pat: Thanks mate i did realise that and stick to NGK causei know their gear!
Deeds: Cool mate! I think i might try 6s again... just to see how it acts ( yeah i know.. covering up for a badly tuned carby still!)
LXCHEV: I'm running .035 gap ( if i could read my feller guages it would help too...) and I dont seem to have a problem as such. I might bring the gap down a little seeing what you guys have been told.
I'm not overly concerned about a fouled set of plugs now and then, i garee with Deeds, $22 and half an hours work is worth it to have it running right! Also now that ive got a second set of 7s, i'll be buffing my old fouled set up on the wire buff to bring them back up to usable and rotate them with the new set as needed.
I'd like to try the 6s to see the difference and see how it affects the engine/temps/pinging. Curiosity i spose!
Thanks guys!
Deeds: Cool mate! I think i might try 6s again... just to see how it acts ( yeah i know.. covering up for a badly tuned carby still!)
LXCHEV: I'm running .035 gap ( if i could read my feller guages it would help too...) and I dont seem to have a problem as such. I might bring the gap down a little seeing what you guys have been told.
I'm not overly concerned about a fouled set of plugs now and then, i garee with Deeds, $22 and half an hours work is worth it to have it running right! Also now that ive got a second set of 7s, i'll be buffing my old fouled set up on the wire buff to bring them back up to usable and rotate them with the new set as needed.
I'd like to try the 6s to see the difference and see how it affects the engine/temps/pinging. Curiosity i spose!
Thanks guys!
#16
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Posted 06 January 2006 - 07:11 AM
Tiny,
I use 6's all the time in my own car but it is true that colder plugs make more power and torque.
The trick with the colder plugs is keeping them clean, run the 6's around town and change to the 7's after scrutineering at the track.
Years ago when I was using heaps of nitrous I would run 9's with a non projected tip, great performance but quick to foul at idle (a shot of N2O only (no enrichment fuel) at idle cleans them up quick !!)
The bigger the gap the more power, I run 040" min with Holden HEI. The only reason to close the gap is if misfiring occurs. Best to experiment.
I use 6's all the time in my own car but it is true that colder plugs make more power and torque.
The trick with the colder plugs is keeping them clean, run the 6's around town and change to the 7's after scrutineering at the track.
Years ago when I was using heaps of nitrous I would run 9's with a non projected tip, great performance but quick to foul at idle (a shot of N2O only (no enrichment fuel) at idle cleans them up quick !!)
The bigger the gap the more power, I run 040" min with Holden HEI. The only reason to close the gap is if misfiring occurs. Best to experiment.
#17
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Posted 06 January 2006 - 07:17 AM
1.016 mm. Wonder if that's the current drama with mine? Feels like it's missing spark at 160km/h. Might have a play as well.
#18
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Posted 06 January 2006 - 10:42 AM
Yella, you shouldn't have a prob with that gap if you have an electronic dissy. I was running mine out at 60 thou (1.5mm ) but the guys on the dyno reduced it to 40 thou (1.3mm i think) as the carby was really rich at idle and stopping the spark from jumping.
#19
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Posted 06 January 2006 - 11:34 AM
Thanks for that Andrew! I didnt realise that the colder plugs give you more power per-se, is there a reason behind that that you know of? or is it just to bring the temperature of the combustion down to eliminate pinging ( and allowing the use of more boost/fuel whatever without the pinging).
I think i'll stay around 32-35 on the gapping that sounds like the happy medium.. Ive opped mine up now to almost 40 and something doesnt feel quite right... I havent driven it yet, but at idle and free reving it feels a little Ummm harsh.. not as smooth as the last plugs change.
Jewey: 60 thou!! Wow! i' surprised you got a spark across that canyon! LOL
Anyway, Thanks again for the tips and advise its all greatly appreciated! Keep it coming! Ive got lots more to learn
Cheers
I think i'll stay around 32-35 on the gapping that sounds like the happy medium.. Ive opped mine up now to almost 40 and something doesnt feel quite right... I havent driven it yet, but at idle and free reving it feels a little Ummm harsh.. not as smooth as the last plugs change.
Jewey: 60 thou!! Wow! i' surprised you got a spark across that canyon! LOL
Anyway, Thanks again for the tips and advise its all greatly appreciated! Keep it coming! Ive got lots more to learn
Cheers
#20
_devilsadvocate_
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Posted 06 January 2006 - 01:34 PM
Colder or hotter plugs dont do anything to improve horsepower, that is determined by the plug placement, firing voltage and gap.Thanks for that Andrew! I didnt realise that the colder plugs give you more power per-se, is there a reason behind that that you know of? or is it just to bring the temperature of the combustion down to eliminate pinging (
High horse power motors/( when compared to motors of the same cylinder volume) produce lots of heat of combustion( higher temperatures), no heat no expansion of gas-no power stroke. The spark plug itself wont change the heat/temperature of combustion.
The major difference, not the only difference, between construction of plugs of different heat ranges is the length of the exposed centre electrode. If it gets too hot it can preignite the mix, pinging. A colder plug has a shorter central electrode.
#21
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Posted 06 January 2006 - 01:49 PM
This has been a very interesting read i think i will be trying out the 6's now, i know about the pinging but i'm interested to know what you guys say about the damage it can do.
#22
_Yella SLuR_
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Posted 06 January 2006 - 02:12 PM
Most interesting read.
Tiny, HEI ignitions do 60 thou (1.5mm) gap standard. While it's good for general driving, I think it's too big for high revs, well that's my current experience anyways, could also be that the Bosch coil isn't up to the task. I'm going to get a spare set of plugs and have a play see if that makes much difference.
Tiny, HEI ignitions do 60 thou (1.5mm) gap standard. While it's good for general driving, I think it's too big for high revs, well that's my current experience anyways, could also be that the Bosch coil isn't up to the task. I'm going to get a spare set of plugs and have a play see if that makes much difference.
#23
_Yella SLuR_
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Posted 06 January 2006 - 02:35 PM
Actually, VK plugs might be 1.3mm standard.
#24
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Posted 06 January 2006 - 03:50 PM
Yes VK plugs are at 1.3mm and earlier are about 1.1mm. 1.5mm is good if you have a nice lean mix as the fuel charge is not that thick and will give you a better burn. My carb was way too rich and therefore the spark couldn't jump on occasion.
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