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Author Topic: Spark Plug Heat Range  (Read 5485 times)
EJ_Dave
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« on: May 07, 2002, 11:22:07 PM »
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After reading an article on the Southern Sydney Early Holden Club web page I decided to change to cooler plugs in my grey. I fitted plugs two heat ranges cooler.

The idea is that the plugs and engine run cooler and the heat is not needed to burn off lead deposits as it was in the old days.

I keep pretty good mileage records and have noticed that since changing the plugs my fuel consumption has increased from 13.3l/100k to 14.5l/100k. These values are based on 8 and 10 fills, respectively, for the same time of year, driving over the same route (mostly to work and back every day).

Has anyone changed plugs and noticed the same thing? Maybe the hotter plugs would be better with the type of driving I do where the engine is cold a lot of the time.

Another thing that might be important- I have been running a 71C thermostat. I have just changed to an 81C one for the Canberra winter- the heater works alot better too! Maybe that will improve the mileage.

I look forward to hearing your thoughts.

David
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smithy
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« Reply #1 on: May 08, 2002, 07:02:03 AM »
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hey dave, ive heard a few people mention they run hotter plugs especially when running ULP with a lubricant. im about 1-2 (maybe more) months away from getting my FC on the road after a rebuild. its running a slightly warm 186 but id be really interested to know how you go with the hotter plugs and with the thermostat as i am about to go through another canberra winter myself.
the other alternative is hardened seats and valves installed ? sorry i couldnt be more help
maybe i'll just keep using the girlfriends car then get mine running by summer Grin as im still trying to find a good small size heater to install
smithy
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ChrisB
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« Reply #2 on: May 08, 2002, 08:42:18 AM »
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Hi Dave,

I read the article and changed my plugs to the longer reach as I had 7 threads as the article said and I am trying two ranges colder. I have not done as many miles as you for the test but my old girl seemed to run cooler in the engine bay area which was one of my concerns as I always seemed to have alot of heat under the bonnet. I am also running the 71 deg t/stat and I find my FC runs consistantly 78 to 81 at the back of the head where the sensor is on the FC. I have fitted a VDO gauge to check this. I cant be sure on mpg but here in Canberra I find it runs much smoother and now gets rid of the heat better. I will watch for an update on your beast to see how you go over winter and weather you have more success with a hotter plug range !!!! Maybe hotter during our colder weather might be better.

Regards ChrisB  Cool
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EJ_Dave
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« Reply #3 on: May 08, 2002, 12:06:25 PM »
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Some more info for Smithy and ChrisB

Smithy- sounds like you're running a red so maybe hotter plugs are a good idea to stop deposits building up on them if you use an upper cylinder lubricant with ULP. Standard plugs for Greys are about the hottest you can get so hotter ones probably aren't an option. I already have hardened valves seats so don't need valve lubricant.

BTW I thoroughly recommend a heater- it only took one Canberra winter without it to convince me I needed one. Makes a huge difference to enjoyment.

ChrisB- I don't think the car runs any better with the cooler plugs. Probably not as well when cold but it is hard to tell. It is only because I keep mileage records that I have been able to pick a difference- otherwise I probably wouldn't have noticed.

I don't have a temperature guage but I have always felt that the motor runs pretty cool. Unfortunately I have thrown the old plugs away so I can't put them back in. Next time newies are due I might get hotter ones again. I'll keep everyone posted whether the hotter thermostat makes a difference and if I put hotter plugs in again.

BTW ChrisB how have you hooked up your temperature guage ie is the sender for the warning light still connected too?

David
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ChrisB
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« Reply #4 on: May 09, 2002, 02:18:03 AM »
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Hi Dave,
I have mounted the gauge seperate and I am not using the original sender as you have to use the VDO sender with there gauge. The original gear is tucked away. The reason I changed to the gauge was only because I felt I had alot of residual heat under the bonnet. With the longer plugs this seems to be much better. I even fitted the fan blade off an EK to get more air, but that didnt help as much as the plugs did.

ChrisB  Cool
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Hewart
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« Reply #5 on: May 15, 2002, 12:06:01 PM »
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G'day guys...

Good to see this discussion taking shape.... I must applogise, I've been a bit bust of late, but Alan actually wrote a "follow-up" piece about spark plugs in our March newsletter  Smiley ... not sure if it relates exactly to what you guys are talking about, but I've finally updated our club page and you'll now find that new article there at... http://www.geocities.com/ssehcc/plugs2.html or go to the newsletter page on the site and you'll be able to find it.....

And keep me updated on your discoveries......

Cheers...
Les...
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keithu
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« Reply #6 on: May 25, 2002, 01:14:35 AM »
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Hi dave  what plugs did you use and what plugs do you use now   that sounds like a good idea ,
the thermastate you changed from 71 to 81% is also a very good idea allthow you wolud have to be carefull in colder weather conditions  were do you live dave the area climate would make a difference  take longer to warm up  regards keith Cheesy
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EJ_Dave
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« Reply #7 on: May 28, 2002, 09:27:46 PM »
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G'day Keith,

I live in Canberra (brrr...) and do mainly short trips (to work). I changed the thermostat from 71C to 81C to help the engine warm up a bit quicker (and make the heater warmer).

I now run NGK BP6S plugs that are roughly 2 heat ranges cooler than the BP5S plugs it was running (standard fitting recommended by NGK).

I started this string because I noticed that my fuel economy was not as good with the cooler plugs and wondered whether the hotter ones might be better considering where I live and the type of driving I do. I fitted the hotter thermostat because I thought if the engine warmed up quicker it might run more efficiently. I probably have almost enough mileage data to report if this has made any improvement.

I checked and re-gapped the plugs on the weekend and they did not have any carbon deposits so it looks as if they are running OK.  The engine has hardened valve seats fitted and has run exclusively on ULP for the past 2 years.

Will make a post when I know about the economy with the hotter thermostat.

Regards,

David
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keithu
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« Reply #8 on: May 28, 2002, 09:42:59 PM »
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HI dave good to here from you  , seems youve done your home work there dave  good show mate ,
i hope you get good results from it,
canberra hey mhh she a cold ol hole he he .
ive been there but to cold for me im in qld. dave sunny
one day  bueatyfull the next  so they say .
anyway  i guess this wouldnt be the same for me here .
as our climent is a bit different to yours .
thanks for the info  dave and good luck with the experiments  , once a gain good to  here from u  mate
keep on  holden ing he he look forward to your next post results       keith
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ChrisB
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« Reply #9 on: June 26, 2002, 09:07:55 AM »
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Hi EJ dave,

Just an update, I have just done the run to Robertson, and sat on 60mph there and back, worked out at 25 mpg which is not that different from the last highway run I did. 28 mpg. The difference this time is I ran on ULP with the FLASHLUBE additive. This is about $2.85 a bottle / tank and seems really good. No pinging, no o/heating. I dont have hardened seats and dont wish to pull the head until I have too. I tried MIllers for ULP on the last highway run and it was great but at $11.00 a bottle / tank it is just too expensive.
I think the plug range for a good condition motor works well, but I dont run my bus every day.

Regards ChrisB  Cool
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