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MG Midget and Sprite Technical - plug colour

hi all,
photo of colour of plugs. sooty round the ring (pardon the expression) and whitish tips. is this still rich.
thanks bob.

bob taylor

Can you try another photo... this is to blured

From what I can tell... it does appear to be rich

Im wondering if the plug gap is incorrect (to wide) or wrong plug temp as in the plug is to cold

Prop
Prop and the Blackhole Midget

hi prop,
new plugs BP6E 25 thou gap. will try get better piccy tomorrow.
thanks mate.
bob taylor

BP6 is a bit cold, but still not out of bounds

Peter burguss made the suggestion to use 35 thou about year ago which ive gone to with good success simply because of all the chemical trash additives that are now part of our daily fuel blends thanks to big oil

Id also try cleaning the plug and laying the plug on a good clean piece of engine block metal and spinning the engine over a few times and observing the color of the spark . It should be a crisp sharp blue whitish in color if its yellow or worse organish in color... then id explore that as an indication to the problem...if it is, trim back about an inch your spark plug cables at the dissy cap, and clean and brighten the screws that secure the cables into the dissy cap

Prop
Prop and the Blackhole Midget

will do that prop, thanks for your help.
bob.
bob taylor

Dont jinks it yet with a thanks...buy some hot dog franks and marshmellows just incase to roast over the midget fire of my advice

:-)

Prop
Prop and the Blackhole Midget

Looks lean to me from the tip, but was running rich at one point from the soot elsewhere.

I would do a 30-35 thou gap to accomodate for modern fuels.

Clean them with a wire wheel/brush and go for a decent drive and see what they look like then. It doesn't look dangeriously lean, but you might benifit from a flat or two out on the jets.
Roadwarrior

Don't forget, If you are using plug colours for checking full throttle mixture you really need to give it a hard run and pull up on the side of the road and check them there and then , NOT when you get back home through traffic etc
willy
William Revit

Yes, a 'plug chop' is the way to go.

...and a '6' is not a cold plug.
Dave O'Neill 2

Road warrorior

That was throwing me also... I wasnt sure if I wasnt seeing the whole blurry picture

Kind of unusual to see it rich on the outside and lean in the center at the same time as you pointed out

You have a point willy

Prop
Prop and the Blackhole Midget

Honestly ,apart from the blurry pic it doesn't look too bad DEPENDING on when they were pulled
Full power plug colour should be clay/biscuit colour in the middle and on the darker side of grey on the outside but not damp, You should be able to touch the grey part without colour coming off on your hand

Plug reading is a bit of an art
It's not hard But you should really understand when to pull the plugs and what you are looking at before using it as a guide


The ultimate way to read the colour is the backside of an exhaust valve
On our old Chev we had the front header tube removeable so that the back of the valve could be seen through the port
The advantage of this method is that the colour doesn't change as quickly as a plug does allowing you to go out and do a hard lap or three, roll back to the pits and pull the pipe for a look - - plugs would have changed colour by this time. If relying on plug colour alone the reading would have been compromised.

willy
William Revit

"I would do a 30-35 thou gap to accomodate for modern fuels."

I don't get that. Can you explain why? Are modern fuels more conductive than old fuels were? They would have to be if you open the gap by up to 40%.

If you have a high energy ignition, then you could open the gap, and if you raise the compression significantly, you could close the gap. But I wasn't aware that modern fuels affected the gap either way.

Most cars built today use spark gaps of .030 to .035 inches, but I think that's to do with them using modern high energy ignition systems, and having more efficient combustion chambers. Our old dogs are quite happy at 25thou. Mine old dogs certainly are, and they use modern fuels. ;).
Lawrence Slater

Lawrence
My thoughts exactly
With standard ignition I just can't see big gaps working
BUT I'm happy to be educated

willy


William Revit

I've not found A-series or Triumph engines to be especially sensitive to plug gaps but, if you have enough voltage, bigger is usually a tad better. The old rule of thumb for a spark used to be 1000 volts for every 1/000 of an inch. So if you have a 40,000 volt coil you're OK with a big gap. Modern plugs and coils might well have different rules of thumb.
Nick Nakorn

A larger gap requires more voltage and can give a 'stronger spark'. It also takes slightly longer to jump and can counter retardation you sometimes need to put into the system to combat the lower octane ratings etc in modern fuels and help avoid pinking and the like. It might be nothing you'd notice on a road car in 'good fettle' and if it's running fine on 25 thou, then it's fine. I can't give it to you any more in depth than that i'm afraid, I simply don't have the raw data. There's all sorts of differences now, not just in pure octane numbers, but also how the fuel burns and the additives they put in etc. I just find it's better and that people who know stuff also agree (such as Peter Burgess) leads me to believe i'm not doing a bad thing advocating it. Cheapy coils might not last as long, as might not the points, but a good coil and electronic (magnetic or optical) ignition will be happy with such gaps. Data sheets with some such igniton systems even advise as such. The MGB engine ignition spec (which I have more experience than Midget engines i'll admit) even advocates a 35 thou gap for the later 45D dissy engines.

I usually set my plugs to a 'slack' 30 thou to end up at 31/32 or so and in time as the gap increases you hit 35 thou or so. I'm no mega expert but I have done a few engines and they seemed happy with that plug gap.

Going back to plug colour, though; plug cutting aside, you have to assume he drove the vehicle under varying loads and conditions and that the plugs we are viewing are around the idle/just off idle zone. If they look that pale now, they will surely become paler when the fueling demands increase under load/throttle. Hence my suggestion for maybe a couple of flats out, and see how you go.

If you really want to give it a good tune, take it someplace you can 'give it some' and take the vehicle up to speed, then immediately neutral the car, engine off (at the same time), and coast to the roadside to check plug colour. This is the only way to 'see' what's going on at that engine speed/load (unless you can also see the backside of the valves). This can help decide if you have the carbs right and maybe even needle choices.

But don't go crazy. If you're not making some racing machine, get it 'close enough' then just enjoy driving it! You can easily over-complicate things and at the end of the day, these are cheap and cheerful cars for the everyman who wants some spring in his step. Drive it accordingly. I think i've waffled on enough...
Roadwarrior

Well that's pretty much what I said then. Modern fuels don't make it possible to run a bigger gap, high energy ignitions do. But that's not why Bob's plugs look sooty.
Lawrence Slater

Roadwarrior

We don't Have to assume anything-

You said and I quote--

"Going back to plug colour, though; plug cutting aside, you have to assume he drove the vehicle under varying loads and conditions and that the plugs we are viewing are around the idle/just off idle zone. If they look that pale now, they will surely become paler when the fueling demands increase under load/throttle. Hence my suggestion for maybe a couple of flats out, and see how you go"

It's very dangerous to assume------especially when giving people advice- He may have pulled them on the highway or even after a cold start - who knows-not me that's for sure.

That's what I'm saying, You have to know what you're looking at and understand it before jumping to conclusions

willy

.
William Revit

Doesn't look too bad.
Sometimes plug chop tests, removing plug after switching engine off says more about the heatrange of the plug. If you put in BP5ES plugs, which were the OE Metro spec till upped to BP6ES later, the plugs will look whiter/weaker burn as the plug will burn hotter and remove crud. If you put BP7ES plugs in they would be a little blacker looking as they wouldn't run so hot. The mixture will not have changed just plug temp.
We tend to use BP6ES for Fast Road and 7's for most race applications.

I don't always know why things work but we have had to increase gaps from 28 thou to 32/35 since 1996 to get best results. I only report what we have found :)

Peter
Peter Burgess Tuning

hi all, just to keep you informed. after the piccy of plug, on starting car the next morning it needed full choke which it has never needed before and when warmed up it would not run any good which told me it was weak. took tops off carbs and set jets level again and undone 9 flats as 12 before was much to rich.put elec ign back as points made no difference. run car for a few miles, pulled plug and no 1 was brown and 4 was black, made slight adjustment to make weaker and waiting to test when it stops pissing down. runs good when stationary revving and tickover better. looks to be on the right tracks.
thanks for all your help and fingers crossed.
regards bob.
bob taylor

Cheers Peter
William Revit

How old is the gas in the tank

Prop
Prop and the Blackhole Midget

hi prop,
gas only 3 days, i use it regularly. prop i think the problem was the jets and where as before i had no adjustment left to weaken, with the new jets its very sensitive and i might have been too heavy handed in adjusting. car started lovely this morning in the garage with half choke but not run out yet as not stopped raining,but feel confident this time.
regards bob.
bob taylor

Im wishing you luck bob,

Its been also raining like a freak here for the past 3 days, im fearing all the condenstaion is going to make my car run like grandma

Prop
Prop and the Blackhole Midget

William

Yeah it is a road to ruin to assume things.
He did present a blurry pic, stated the plug type and that he pulled the plugs after he was done. Seems highly unlikely he would fly into his drive/garage at 6000rpm and immediately turn off the engine. Peter is very right about heat range vs colour, but as he told us the plug type and that he has a standard engine (he didn't say he has anything else and has made other threads indicating it's standard) and that he likely wasn't thrashing it as he removed the plugs leads me, from experience, to see that the pale tips on the plugs point to a slightly weak mixture at idle/low speed leading to lean across the range from standard needles. A couple of flats or so correction needed. He then pointed out, had trouble starting and it wouldn't run well. He then adjusted the mixture a few flats different and found he was more in the ballpark to adjust maybe another 1/2 flats to get it right. This points to me being correct to lead him down that route of gradual enrichment.
Not trying to rub anything in your face here, or trying to sound defensive (I am always happy to learn!) but I think I was justified to say what I said.
Roadwarrior

Roadwarrior

All good

Have a nice Easter break

willy
William Revit

Road warrior,

I, and the BBS, appericate the strength it took you to crawl up on that cross of crucifixion and the beating you self administered to solve this issue ... we and jesus will never forget your sacrifice to this topic and cause. jesus is proud and now he smiles, job well done...you alone earned it

Haha

Happy easter

Prop
Prop and the Blackhole Midget

Haha, I guess I did come across as hard done by.

I'm just used to dealing with customers who don't believe anything I say because it usually involves them spending more cash. I have a habit of justification till blue in the face.

Cheers!
Roadwarrior

Road warrior

Haha

I was just having fun with you, alot of times stuff comes out in text form a bit scewed from what was intended...I just couldnt resist the temptation to have a go with you

Customer service... I hear yeah, thats a crazy occupation and you see it all in people


Prop
Prop and the Blackhole Midget

This thread was discussed between 01/04/2015 and 06/04/2015

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