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Any Sparkplug Readers Out There?

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Martinld123

Martinld123

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sparkplugs.jpgMy car is running great but needed to work on something, lol. Are there any people out there that can read my plug condition? Here are my sparkplugs with number three standing out different that the other three. Any ideas? or don't worry and go for a drive, lol. Thanks Marty
 
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I don’t see any pic of your plugs attached.
 
I would say number three and four good and the rest are weak mixture , too white .
 
How would I fix this? Turn out front carb one or two flats to give cylinders 1 and 2 more fuel? That is only way I know to give it more fuel. Thanks Marty

QUOTE=Healey Nut;1099101]I would say number three and four good and the rest are weak mixture , too white .[/QUOTE]
 
Why would one plug be too lean and one too rich, being fed by the same carb? Something else at play (note the lumpy deposit on the 'rich' plug). I'm not sure the three are too lean, gasahol essentially creates a lean mixture (David Nock recommends rich needles to compensate).

Here's new plugs on my BJ8 after 5,200 miles (mostly with gasahol, but one can never be sure):

Plugs-5200Miles.JPG
 
My guess FWIW. Mixture to lean, plug range to cold, timing to far advanced. #3 may have a bad wire. Remember this is only my guess.
 
I agree with Bob and would shoot for a consistent reading across all four plugs before making any carb adjustment. Perhaps a leak-down would tell you if there is something anomalous in#3.
 
pdplot said:
I concur. White plugs show a lean mixture. What plugs are you using?
Click to expand...

I am using NGK BP6ES plugs. Maybe too hot a plug? BP8ES is a cooler plug for a normal BN2 engine. Car is a BN2 with M cam, larger piston, and M size carbs. Rebuilt engine 4000 miles ago. Thanks Marty
 
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Martinld123 said:
I am using NGK BP6ES plugs. Maybe too hot a plug? BP8ES is a cooler plug for a normal BN2 engine. Car is a BN2 with M cam, larger piston, and M size carbs. Rebuilt engine 4000 miles ago. Thanks Marty
Click to expand...

Check that the plug gaps are the same. I did not see any pictures of the plugs in the first post but the one with the Champions look like the gap on the third plug is to small. That would probably cause earlier firing.
 
plugs 2 and 1.jpgplugs 4 and 3.jpgSame plugs but in different order, left to right, 2, 1 and 4, 3 after I turned front carb out two flats and ran car for 30 miles. Whitish color mostly light brown now. Confused with 3 and 4 plugs getting darker also but did not touch back carb. Plug three was the darkest one in first post photo. Might turn two flats back and try cooler plugs?
 
I'd argue your photos show it to be a carb-related issue rather than ignition.

The richness in the front carb also affects the rear carb.

Make sure the fuel level in the jets is the same or at least make sure the float level is the same and the jet needles are not rubbing.

Check the jet drops with a dial caliper - are both the same?

Do you get the "clunk" when you lift up the slides and let them drop?
 
Clunk drop sound is loud and clear in both. The M Carbs are year or two old from Moss Motors. I guess the cross over pipe played a roll in my rich front carb effecting back carb. I will need to get my tune up books out. Some believe to do what you say but others believe final tune is by ear or vacuum. Not looking forward to this, lol. Thanks Marty


steveg said:
I'd argue your photos show it to be a carb-related issue rather than ignition.

The richness in the front carb also affects the rear carb.

Make sure the fuel level in the jets is the same or at least make sure the float level is the same and the jet needles are not rubbing.

Check the jet drops with a dial caliper - are both the same?

Do you get the "clunk" when you lift up the slides and let them drop?
Click to expand...
 
G’day Marty,
I also use NGK spark plugs, but I use B6ES. Without the projecting nose.
Cheers,
Alwyn
 
I decided to try a cooler plugs going from BP6ES to BP8ES. Then I richened front carb by two flats (1 & 2 were light gray color) and leaned out back carb two flats (3 & 4 were dark black with carbon). All plugs look the same now a light brown or light black after 40 miles. No carbon build up on 3 and 4. Longer distance soon for better test. Anyone heard of tuning by plug color, lol?
 
Reading your plug colour is the very best in my opinion to CHECK carb tune. To adjust the carbs I set my jets soully by idle speed. Take it for a ride, get it to idle relatively slowly, hook up an electronic tach ( a diagnostic one not an in dash unit) and adjust each jet for the highest idle you can get just on the jet adjustment. When you get each carb at the highest idle speed on the jet, then adjust your base idle speed either by throttle stop or slow run screw depending on which model SU you have. Do your jet adjustments slowly so the system has time to get it. If it appears to be loading up because it was overly rich then hold throttle at about 2000 rpms for 30 seconds or so to get it cleared out.
 
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