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#1 Series 3 spark plugs colours

Posted: Tue Oct 30, 2018 5:29 pm
by chris420sa
I have just pulled all the plugs on the V12 after a 20 mile run in fairly cool weather and thought it would be helpful if a member or two could please advise what fuel mixture adjustments they would recommend on each of the four Strombergs ....and any other adjustment. The ignition timing is OK (slightly advanced versus the ROM spec), new dizzy cap, fairly new leads, fairly new plugs, great spark, only centrifugal advance (I have "plugged" the vacuum retard hose, given that the retard is an unnecessary complication), can't detect any vacuum or other leaks, fuel pump seems to be delivering OK....
Colours below refer to the central electrode, plugs numbered from front of engine
A Bank
1. White on one side, grey on the other side
2. Light grey on one side, dark grey on the other side
3. White on one side, light grey on other side
4. Dark grey to black all round
5. White on one side, dark grey on the other side
6. Dark grey all round

B Bank
1. White/light grey
2. White/light grey
3. White/light grey
4. Dark grey
5. Dark grey
6. Light grey

I should also mention that there's a flatspot at about 3,000 rpm (which was why I pulled the plugs)

I look forward to your welcome feedback.
Best regards
Chris

#2 Re: Series 3 spark plugs colours

Posted: Wed Oct 31, 2018 12:42 am
by abowie
Unless you're running leaded fuel this is not really a useful test any more.

#3 Re: Series 3 spark plugs colours

Posted: Wed Oct 31, 2018 5:25 pm
by jagwit
chris420sa wrote:
Tue Oct 30, 2018 5:29 pm
B Bank
1. White/light grey
2. White/light grey
3. White/light grey
From this info, it seems there is a problem with the front carb on the B-bank. Seems to be running lean almost as if its not feeding any fuel (or way too little).

I would remove that air filter, and while looking into that carb (with safety glasses), rev it up briefly with much throttle and observe if 1) the air valve (that cylindrical "piston" in front) lifts as much as the rear carb; 2) you can see fuel being drawn into the carb.

It might also be worth while to check if the butterfly on that carb actually opens before you start. If somehow the throttle linkage came loose....

#4 Re: Series 3 spark plugs colours

Posted: Fri Nov 02, 2018 12:48 pm
by JJC
Can always learn something new ! Why is reading spark plugs no longer a great way to get a handle on mixture, timing, etc ., since no one really using anything but unleaded gas these days ?


Thanks.

FYI.....I do it all the time !

#5 Re: Series 3 spark plugs colours

Posted: Fri Nov 02, 2018 5:44 pm
by jagwit
Even with unleaded spark plugs can still tell something. (I'm certainly no spark plug whisperer...)

It most certainly will tell you if the piston is running rich = very black
Too lean = too white and clean

I can not see how a spark plug can tell much about timing. Maybe there's something when the engine detonates a lot?

#6 Re: Series 3 spark plugs colours

Posted: Sat Nov 03, 2018 9:58 am
by malcolm
I believe pinking from too far advanced timing can cause burning off the spark plug tips.

#7 Re: Series 3 spark plugs colours

Posted: Sat Nov 03, 2018 11:47 am
by jagwit
Here's an example of my car 's plugs, which I recon is one of the best tuned S3's in South Africa - IMHO.

Inner ones #2 on each bank, outer ones, #6 on each bank:
tn_20181103_132041.jpg
tn_20181103_132041.jpg (138.54 KiB) Viewed 1514 times
Relevant info;
  • The carbs on my car are perfectly balanced;
  • fueling set as good as I can;
  • needles changed to reduce overfuelling on full throttle (it was making visible black smoke on full throttle pulls);
  • Lumenition ignition;
  • Vacuum advance (vacuum direct from intake manifold);
  • I add 500mL of 2-stroke oil to the fuel every time I fill up (only when fuel gauge is well below 0)

#8 Re: Series 3 spark plugs colours

Posted: Sat Nov 03, 2018 12:04 pm
by Ole-xke1974
Philip, I get all of the above except the addition of 2-stroke oil. Can you explain ?
FYI, I once accidentally put petrol for a 2-stroke moped (~4% oil) in my car and experienced that it ran smoother.

#9 Re: Series 3 spark plugs colours

Posted: Sat Nov 03, 2018 12:15 pm
by JJC
Philip: Your plugs look perfect ! I am also curious as to the addition of two stroke oil. Always several ways to skin the cat......love to hear !

Thanks

JC

ps: I'm guessing the carbs are set more on the lean side.....that's where I found my sweet spot.

#10 Re: Series 3 spark plugs colours

Posted: Sat Nov 03, 2018 12:44 pm
by jagwit
Ole-xke1974 wrote:
Sat Nov 03, 2018 12:04 pm
Philip, I get all of the above except the addition of 2-stroke oil. Can you explain ?
FYI, I once accidentally put petrol for a 2-stroke moped (~4% oil) in my car and experienced that it ran smoother.
I BELIEVE (no hard evidence..) there to be the following advantages of using 2-SO in our old cars:
  • Reduces rust in mild steel fuel tanks - fuel evaporates from sides, leaving thin oil layer
  • Lubricates fuel pump - FWIW;
  • Shows presence of fuel leak - fuel evaporates but coloured 2-SO stays thus showing the leak - ask me how I found this particular benefit ...;
  • Lubricates moving parts in carb;

Now comes the more important ones:
  • The 2-SO in the fuel APPARENTLY (no hard evidence) softens the carbon deposits behind the intake valves, and over time this carbon is sucked/shaken off thus improving engine breathing efficiency;
  • Ditto the carbon on the piston top and inside the combustion chamber;
  • Ditto the carbon between the rings and the piston - this could result in improved compression as the rings work loose and thus seal better; I have actually seen this happen on a Land Rover Discovery 1 V8 where #5 was way down on compression relative to the others when I got the car. After driving about 5 tanks on the 2-SO mix, #5 compression was on par with the others;
  • 2-SO does not burn and thus some of it is blown out the exhaust port and now you have the same effect on the exhaust valve and port as the intake valve;
  • Lubricates the exhaust valve stem - reduces valve stem and guide wear.
IMPORTANT!!
2-SO should NOT be used on a car with CAT's or Lambda sensors. 2-SO can contain heavy metals which could destroy both.

As for your experience Ole, I doubt any of the performance related effects mentioned above could come into play immediately, so I can not offer an explanation as to why you experienced it as running smoother.

There is a Youtube video that shows a lawnmower running happily on a 50:50 mix of pertrol/2-SO. THIS I can attempt to explain if we consider that the lawnmower was most likely running pig rich and the added 2-SO was merely effectively leaning out the mixture to a point where it was running leaner.

#11 Re: Series 3 spark plugs colours

Posted: Sat Nov 03, 2018 12:56 pm
by jagwit
There is another benefit I forgot about:

Lubricates the exhaust valve stem - reduces valve stem and guide wear.

#12 Re: Series 3 spark plugs colours

Posted: Tue Nov 06, 2018 2:04 pm
by chris420sa
Phillip - the case for the defence of 2 SO is well made. I'll definitely give it a try.

Following your advice, I checked that the front LH carb was operating in unison with rear LH carb etc. All fine.
Then set the mix using the screwdriver piston lift method. Front RH carb was definitely running too lean, the other carbs only needed minor adjustment. Went for a good run, plugs all perfect and no flat spot.

If this success continues what will I do with my spare time!

All the best
Chris

#13 Re: Series 3 spark plugs colours

Posted: Tue Nov 06, 2018 2:23 pm
by jagwit
chris420sa wrote:
Tue Nov 06, 2018 2:04 pm
Went for a good run, plugs all perfect and no flat spot.

If this success continues what will I do with my spare time!
Randomly tune them out and then start again? :bigrin:

Nice to hear its sorted!

#14 Re: Series 3 spark plugs colours

Posted: Wed Nov 07, 2018 12:00 am
by PeterCrespin
2-stroke oil is specially blended as low-ash, in order to leave, you guessed it - as few deposits as possible when much of it burns. The idea that burning extra oil reduces deposits is bizarre on its face. By that reckoning the cleanest engines would be the ones with knackered inlet valve seals, worn oil rings and black goo dribbling out of the tailpipe like a Trabant on heat. Even synthetics burn eventually. Earlier this season, F1 teams were banned from using a reserve of engine oil as extra fuel to get round the fuel consumption rules.

Being a Jaguar driver, it goes without saying that I can rationalize almost any automotive excess. But to deliberately pollute more, in such a wanton and unnecessary way, shocks even me. I've raced two strokes, I love them in some contexts. You've never felt a powerband until you've ridden an old-school stroker as it comes onto the expansion chamber and takes off like the proverbial scalded cat. But the likes of Ford et al had to admit defeat a few years ago when the industry finally abandoned them, despite amazing advantages over 4-strokes in other respects. Even with direct oiling and running on neat petrol, and the brain-power of consultancies like Ricardo, the big firms had to kiss their heavy investment goodbye because they simply couldn't be made to run clean enough no matter how much technology they threw at them.

So now we're supposed to add it deliberately to vehicles that do fine without? Those of us with kids and grandchildren have already some explaining to do on heavy metals etc.

#15 Re: Series 3 spark plugs colours

Posted: Tue Nov 13, 2018 9:43 am
by Woolfi
"Vacuum advance (vacuum direct from intake manifold)"
This is WRONG. The vacuum has to be taken from a port at the carb, "called tappered edge". Few carbs have this port. For my EV12 I had to drill a port to one carb. The port has to end roundabout 1 - 3 mm in FRONT of the butterfly. If you presse the pedal slightly (part throttle) , the edge of the butterfly has to by exactly at this port, to generate maximum low pressure. At full throttle, the amount of vacuum is low.
If you take the vacuum form the intake manifold, you have maximum vacuum at iddle. Therfore 10 + 12 degree = 22 degree of pre-ingnition. This is to early.
The discussion about this is long. In the forum and in the internet you can find all professionell advice, you need to understand this.
Read the information from below, try to understand, drill your carb. The result will be much better.
Regards Wolfgang Gatza


https://www.britishvacuumunit.com/ported-vacuum.html

#16 Re: Series 3 spark plugs colours

Posted: Tue Nov 13, 2018 12:51 pm
by MarekH
This thread is about spark plug colour.

Whilst there is nothing wrong with the concept of ported vacuum, it doesn't bring anything to the table that manifold vacuum doesn't already, so I wouldn't go to the trouble of implementing it over and above that of going the conventional manifold vacuum advance route.

This has been covered in other threads already, most notably by Philip quite recently.

kind regards
Marek

#17 Re: Series 3 spark plugs colours

Posted: Tue Nov 13, 2018 5:19 pm
by jagwit
Woolfi wrote:
Tue Nov 13, 2018 9:43 am
"Vacuum advance (vacuum direct from intake manifold)"
This is WRONG.
It is NOT wrong. I still want to verify this statement but I believe that just about every Series 1 and 2 E-type runs on manifold vacuum advance. A '68 S1 4.2 I recently worked on certainly did have manifold vacuum advance.

I challenge you to read the following topic and debate the subject further there: http://forum.etypeuk.com/viewtopic.php?f=3&t=12885
Therefore 10 + 12 degree = 22 degree
Quite correct. But clearly you don't understand the difference in timing requirement for

IDLE @ 800rpm

vs

FULL THROTTLE @ 800rpm

#18 Re: Series 3 spark plugs colours

Posted: Tue Nov 13, 2018 10:07 pm
by Series1 Stu
Yawn..................

#19 Re: Series 3 spark plugs colours

Posted: Sat Apr 20, 2019 8:37 am
by Adamski
I know I'm a bit late to this topic but balanced my carbs by using a Stromberg air flow meter, four Coloutrtunes (one in centre plug of each carb bank.) and a needle mixture adjusting tool that goes into the top of the dashpot.
The Colourtunes had a good effect of identifying a lazy carb at tick over. Now this is not an exact science but it does tell you if all are burning well at tick over (needed richening).
I did mess around for hours and the cross balancing of vacuum across banks is a real pain but eventually you get into the ball park. What is quite surprising is that without the vacuum air flow meter you think they're all pulling the same but until you put it on you realise how out of sync they all can be.
Once done I suggest just leave it alone apart from minor tick over adjustments in equal increments.
Otherwise my car is standard UK spec. with upgraded ignition and cooling and carburation rebuilt and temperature sensors deactivated(Screwed up tight) And the various vacuum tubes only serving the retard unit and cross balancing of inlet manifolds. All other vacuum stuff deactivated
It likes a bit of heat under the bonnet though-Awful!!
I do believe that a visual plug read as still very useful.

#20 Re: Series 3 spark plugs colours

Posted: Sun Apr 21, 2019 9:48 pm
by madjack4
Yet again a debate about ported vac the people that run full vac on a advance unit have not tried ported vac. As a test last week i filled the tank on my s3 v12 roadster on which is just run in after a full rebuild new pistons and liners full set of valves and guides all comprehensions identical and a new set of SU carbs balanced and mixture set spot on with a vac advance did a run of 60 miles with ported vac next day i connected to full vac and did the same run same time of day and virtually same outside temp the car felt numb at low throttle openings with full vac compared to ported vac and the fuel economy was 17% better with ported vac now all the people with full vac fitted please take NOTE and dont tell me my car is not set up right ive been in motor trade for 47 years did my time at a BL dealer and have worked for myself since 1984

Regards Rob