Plug reading

-
Mike 340

Mike 340

Well-Known Member
Joined
Jun 21, 2016
Messages
191
Reaction score
147
Location
Canada
Am I too lean?
20220902_151734.jpg


20220902_151724.jpg
 
Look at it with a magnifier for specks of aluminum from the piston. Then you are too lean.
 
It’s my understanding that you’re not only looking at fuel mixture on the ground strap & porcelain, but timing advance/retard as well. So you could have a perfect fuel mixture but your timing could be off, and vice versa.

I’m not an expert, hopefully someone can confirm or correct what I’ve just said.
 
I remember from school days, that a lean plug has a "white hot" look to it. These don't look like that.
They look slightly worn to me, that's all. The edges of a few of the electrodes are rounded a bit.

Are you having any symptoms suggesting a lean condition?
 
Car seems to run well, no surging or popping. I just thought that they looked a little grey as compared to tan.
Stock 68 340 with 71 J heads with a mild cam, similar to a 68 four speed cam.
18* initial and 34* total.
3310-1 Holley with stock jetting
72 front and 84 rear.
 
Mike 340 said:
Car seems to run well, no surging or popping. I just thought that they looked a little grey as compared to tan.
Stock 68 340 with 71 J heads with a mild cam, similar to a 68 four speed cam.
18* initial and 34* total.
3310-1 Holley with stock jetting
72 front and 84 rear.
Click to expand...
The plugs look rich to me.
The factory 3310 jetting is usually a bit rich for mild small blocks.
 
Mike 340 said:
Car seems to run well, no surging or popping. I just thought that they looked a little grey as compared to tan.
Stock 68 340 with 71 J heads with a mild cam, similar to a 68 four speed cam.
18* initial and 34* total.
3310-1 Holley with stock jetting
72 front and 84 rear.
Click to expand...
Overall for mixed street use, they look OK to me. See a little richness at initialtion on one side of 2 and 4 but not the other. Same w/ 7.

There's reading plugs for problems.
Problems would be things like melted or severly worn electrodes, bad fouling, etc etc,

Then there's reading for tuning which is a little different and what you're asking about.
Really need to know the conditions the spark plug and then put that together with the evidence on the plug.

3310-1 has downleg boosters and spivies on the primary boosters.
The spivies are to redirect (balance the fuel) distribution in its original application - and may or may not be helpful on yours.
In normal daily driving it won't make a noticible difference. On the interstate - maybe, and on the drag strip or more extendend top gear wide open throttle - probably will.
Stock secondary jetting is 76 and the secondary power valve was an 8.5. Secondaries really only come in to play during high speed passing and quarter mile, etc.

All that is mentioned to illustrate how the use plays into what is seen on the sparkplugs. If those plugs are showing 3 quarter mile passes, thats different than if its show 3000 miles of mixed street use.
 
Nothing in there that would concern me. Front half look a touch on the rich side but even that is kind of splitting hairs.
 
I'd probably go with a hotter plug. looks a little cold.
 
These plugs are at 3000 miles of mixed driving. These are also what the factory calls for the plug. I am just getting into tuning.
Thanks for everyone who is giving me information. This is gold, please keep it coming, if there is anything else you see please let me know!
 
GTX JOHN would be a great judge of those. I recommend you reach out to him.
 
They heat range is fine and I run that plug on our
street/strip cars. BUT I do not idle it for extended period of
time any more other than at traffic light and such.
Ground straps look about right.
Examine the porcelain for specks on them or post some closer
pics of them ( My eyes are elderly). Lacking that you are fine.
But 84 jets?
I would be 74 to 76 at Sea level and one smaller size for every 1000 ft
of elevation you are at.
 
Its possible someone changed the secondary block or installed a PV plug in it, then jetted up to compensate.
 
Thank you for your replies.
Yes the secondary metering block has been replaced and has no power valve.
I have checked the plugs with a magnifying glass and I do not see any specs on them. I will try to get some more pictures of the plugs at a closer view tomorrow. I am glad to hear that everything seems to be close.

Thank you again for everybody's help. This is a bit of a learning curve for me. Any suggestions would be greatly appreciated.
 
Dual plane manifold?

What's the redish tinge or is that the lighting.
 
Stock cast iron spreadbore manifold.
Not sure what you mean by reddish tinge? Where are you seeing this?
 
You must log in or register to reply here.
-

Back
Top