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Author
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Topic: Plugs don't colour
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ukracer
Gearhead Posts: 151
From: South Wales UK
Registered: Apr 2003
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posted 06-03-2003 11:36 AM
   
It's that simple. Took the car out for some blasts and plug chops but the traffic was too busy so after about 4 miles (with a few good blasts throught the gears!) I got home and pulled couple of plugs anyway to see how quickly they coloured as I had cleaned them before going out. There was almost no colour on them at all, so how many seconds run time at full chat do you need to get any readable colour on plugs? I know this is a popular subject here (I did a search!) and the info is good but I just can't see any colour to read! Agghh!
Cheers, Martin.
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steve'66
Gearhead Posts: 8826
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 06-03-2003 11:55 AM
Martin,
Check this site out,
http://cochise.uia.net/pkelley2/sparkplugreading.html
SteveW [This message has been edited by steve'66 (edited 06-03-2003).]
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ukracer
Gearhead Posts: 151
From: South Wales UK
Registered: Apr 2003
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posted 06-03-2003 11:58 AM
I did a search and found the site you refer to but my plugs (the threaded portion) are still bare metal after driving, including some good hard blasts. So, how do I get colour on the threads?
Cheers, Martin.[This message has been edited by ukracer (edited 06-03-2003).]
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steve'66
Gearhead Posts: 8826
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 06-03-2003 12:10 PM
Go up a couple jet sizes.  If you had a automaic tranny with a high stall converter and a transbrake you could do a "dyno pull" in your driveway. But that combo wouldn't work for your road races.  I guess you don't have any "freeways" where you can take it up to 80mph and turn it off, coast to a stop and pull a plug at the side of the road.  SteveW
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ukracer
Gearhead Posts: 151
From: South Wales UK
Registered: Apr 2003
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posted 06-03-2003 01:04 PM
Well, I could use our Motorways and we even have some 'good' pieces of road near me (nice uphill grade for 1/4 mile or so) but if I blasted up them and pulled over to check plugs, my reputation locally would be shot (broken down!) and I would probably have to fight off loads of helpful people who would think I had broken down. Plus, of course the Police are a bit hot on this kind of thing! Rest assured I will get around to doing some plug chops but I need to see some colour there! I will take your advice (you have said what I wanted to hear anyway!) and jet up. Is the lack of colour a sign of not enough fuel?
Cheers, Martin.
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steve'66
Gearhead Posts: 8826
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 06-03-2003 05:13 PM
What's your jetting now, 66/74? With one power valve or two? 351w and 600 Holley dp'r right? What kind of fuel?SteveW
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ukracer
Gearhead Posts: 151
From: South Wales UK
Registered: Apr 2003
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posted 06-03-2003 05:23 PM
Yep, 66/74 again now, PV on primary only. 351W/perf RPM/XE268/9.5:1/1 5/8" headers with full exhaust (3" X pipe and 2.5" system straight through to bumpers)600 D/P Holley w/cold air system. Fuel is pump unleaded. Guess that would make it harder to read but leaded went a while ago now!
Cheers, Martin.
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steve'66
Gearhead Posts: 8826
From: Sonoma,CA,USA
Registered: Mar 2000
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posted 06-03-2003 05:51 PM
Martin,Try a pair of 70s in the front and 76 in the rear. The modern unleaded fuels burn clean, that's why we're reading the threads. You need a longer pull to get a reading on the threads. Is your petrol "oxygenated" (mixed w/alcohol, or MTBE's etc) ? SteveW
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ukracer
Gearhead Posts: 151
From: South Wales UK
Registered: Apr 2003
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posted 06-06-2003 11:38 AM
More info (instead of questions!). I gave up on trying to read the plugs as roads do not permit and reverted to using the O2 sensor I have fitted, reading with DVM. Ended up with 66/74 in there and a touch rich on the volts. I know many people do not trust this method but it has worked for me in the past and at least you can read it 'on the fly'. So, it looks like the jets were about right all along, but this engine seems quite insensitive to jetting and also if I disconnect the secondaries, it doesn't seem to make any difference. It has always been like this. I won't even ask what that is about! Thanks for all input.
Cheers, Martin.[This message has been edited by ukracer (edited 06-06-2003).]
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