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Read Spark Plugs

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David_Doan

Jedi Warrior
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Can someone help me read this plug. All four of them look about the same. My guess is that I'm a little rich, but it doesn't look as bad as what's on the spark plug guides. My car sputters a lot at when it's cold, mostly between 1000 and 2000 RPM's. Seems to run fine after warming up ~ 10 minutes of driving. I use 93 octane gas and the timing is set at about 15 at idle and maxes out at about 30 at 3000 RPM.

Plug is a champion N5C.

If it is to rich, will the plugs clean up after adjusting to leaner or do they need to be replaced.

DSC_6168.JPG


Thanks,

David
 
Well, I can see where it says "330." Perhaps if you held it upright, it would be easier to read. :devilgrin:

~Couldn't resist... an old joke from my Dad's drag racing days.
 
Other than being a Champion plug (I just don't like them), it looks OK to me. Adjust the mixture and see if it helps then recheck the plugs. I look for a tan color on the insulator.....any soot or carbon means something is amiss.

BTW.....you can clean them off with a wire brush. It won't hurt them at all.....no need to buy new ones (other than to rid yourself of those Champions! :smile: )
 
I've been studying this plug reading thing for awhile now, and it's really helped me get my MG tuned almost perfectly. There's a lot of info on the internet, if you're interested.

It's hard to tell exactly what color the porcelain is on your photo. Looks a bit grey, and it's supposed to be chalky in appearance. If the bottom of the porcelain (nearest the tip) is grey or sooty, it may be an indication of a rich mixture at idle.

I also can't read your ground strap. It looks like there may be a blue area up above the "elbow" of the ground strap (nearest the tip). If so, your ignition timing may be just a tad off. Ideally, the blue or bluish area on the ground strap should be down just below the elbow, nearer to the the ground strap weld.

Wild guess, from what I see here: you're running a little rich at idle, and your ignition timing is just a little bit off.

Question: Is there a blue or bluish area on your ground strap, and if so, is it generally the same color and position on all your plugs?
 
Looks a little rich to me - when you say sputters when cold, choke on or off? If on, the combination may be too rich. Also, can you define sputters - hesitates? stumbles? misfires?
 
About half a flat rich I think on that carb. How about a plug from the other end.

Don't even think of cleaning it, it is fine.

Use a bit of choke till it warms up, just a bit.
 
Thanks for the quick responses. i took it out for a good hard run, then pulled the #1 plug for inspection. Here's what I found:

DSC_6171.JPG


DSC_6175.JPG


I think now I will adjust the carbs a flat or two leaner and see what happens.

Mark, when you say timing is "off", which direction

JP, My choke doesn't stay on, I just use it for starting. It doesn't seem to help the sputtering when I try to hold it out. Hesitates or stumbles would be how I would describe the sputtering. It doesn't back-fire, just has no power and misses a lot when it is cold and in the 1000 to 2000 RPM range.
 
One flat at a time please. You actually are kinda close. In fact I would try half a flat.

On third thought, think I would call it good and not check for several weeks or so.
 
jlaird said:
One flat at a time please. You actually are kinda close. In fact I would try half a flat.

On third thought, think I would call it good and not check for several weeks or so.
Click to expand...

Thanks Jack, but I didn't change anything yet. I just gave it a couple good miles on the freeway and came back home. The sooty pics from earlier were after a lot of idling.

Also, on the highway, my car struggles to do better than 65 mph. Is that normal for a 948? I'm guessing the factory claimed 80+ max speed is downhill with a tailwind.

I'm mostly trying to address the poor cold start performance. When I use the bugeye for errands, it doesn't run good till I'm on my way home.
 
i may get some disgreement here, but that plug looks lean... dry and white...
 
That is why I wanted to get a few more miles on it before giving some specific advise.

Now may be the time for a few strokes with a soft wire brush to get the carbon off so we can see better the next time. Just the black pls.

65 is about right for a 948 lots of wind resistance on the flat.

Yea I can do 70 down hill and down wind. Good hill and good wind.

Miss Agatha is happy as a tick at 60-65 on the flat, actually I prefer 60, but maybe that is just my age. You know things you did at 20 and 30 you don't even consider at 73. Well, some things.
 
jlaird said:
That is why I wanted to get a few more miles on it before giving some specific advise.

65 is about right for a 948 lots of wind resistance on the flat.

Yea I can do 70 down hill and down wind. Good hill and good wind.

Miss Agatha is happy as a tick at 60-65 on the flat, actually I prefer 60, but maybe that is just my age. You know things you did at 20 and 30 you don't even consider at 73. Well, some things.
Click to expand...

Thanks for the confirmation, I feel like mine is tuned pretty well and has good compression. At least in a bugeye 60 feels like 100.
 
David_Doan said:
Thanks for the confirmation, I feel like mine is tuned pretty well and has good compression. At least in a bugeye 60 feels like 100.
Click to expand...

100 mph in a Bugeye is surreal.
:devilgrin:


Those last set of photos look pretty darn spot on.
Nice "coffee w/ cream" color.
 
The next pix look perfect - don't touch a thing. In terms of the stumble now might be a good time to put oil in your carb dampers. Don't ask me why I think this.
 
Agree with the almost right sceneario. Put some miles on and cut it without idleing. Agree with the dislike for champion plugs, NGK's or Bosch might run better. Wondering what your water temp is? My BE hesitated with the carb setting it currently has when the thermostat would'nt let it get over 160. Changed to 180 and now runs like a top. Could have richened it a bit and probably accomplished the same thing.

Kurt.
 
You are saying that using the choke doesn't help- ??
I have my carbs set fairly well but MUST use the chokes for about the first 2 minutes or I get exactly what you are describing in terms of cold running.
If you pull your choke knob out about 1" or so you SHOULD get a much better run during warm-up.
BillM
 
Gundy said:
100 mph in a Bugeye is surreal.
:devilgrin:
Click to expand...

Yes it is! I've done it a few times and man, what a thrill. :smile:


As for the plugs......the first picture made it look worse than it really was. The later pics are much more clear and I agree with everyone else.....you are pretty close if not spot on. I too would drive it around for a couple of weeks then recheck them.
 
So, tonight I think I found the real problem. After putting the plugs back in, the car ran horribly. Since plugs and wires are what I messed with, I checked all that 1st - Ignition is fine. I noticed that while idling, pulling off the plug wires one at a time neither of the back two seem to change anything - So this now points to the back carb.

When I pulled off the air cleaners (picture of a setup like mine is shown in the pic below. not my pic, I just found it on the web), I found one of the bolt sleeves stuck in the throat of the rear carb. I remember the last time I put them on, I noticed one of the sleeves was missing - I guess it was just hiding. It had the piston pushed up about 1/4" more than normal. The car ran fine when I took it out.

filter_cannister2.jpg


I also noticed that even though the air filter backs had holes for the carb breather on both sides (like an HS4), mine had the HS2 gaskets with only one breather hole, and they were on backwards blocking both carb breathers. I guess this has existed for a long time.

It's all back together properly now, seems to run better. The cold start in the morning will be the real test, should be better now.
 
Wow. yep will start and run better, can I say better. The carb with the sleeve in it was full choke or trying to in any case. I can not believe you were able to balance them. In fact with all that wrong it is a wonder it ran at all.

Just says a lot for our little engines and the lovely SU carbs.
 
I did all the tuning and balancing with the air filters off. On my last drive yesterday, the sleeve must have gotten in deeper.

This morning it started and idled much better, warmed up quicker. Throttle response is also a lot better, clearly making more HP now, hit 75 on the freeway.
 
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