Plug readers

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I always look at every plug when verifying the gap. I’ve seen all kinds of stuff you wouldn’t see if you didn’t look right at them. I think it was a set of Autolites, but it may have been Champions that out of a set of 8, three had a hairline fracture down the porcelain. Have no idea how that happened but I was down to one of the last plugs and found it. Went back though them all and found 3 more, but I needed my magnifyer to see those.

You find all kinds of crap, like the ground wire isn’t welded on correctly. I’ve seen them fall off. Or the ground wire isn’t parallel to the center wire.

Just drives me nuts.
 
Ok, here’s a couple of plugs after a 50 mile cruise yesterday. No WOT runs. I have added vacuum advance FBO billet distributor with 20* initial, 14* mechanical @3200rpm, and 12*@12” of vacuum per Dons recommendation. I think I’m really close here. What do the gurus think. 2 plugs here with 2 different heat ranges.
Plug 1

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D38115B2-93A5-4E9F-9AA9-AEF7D8D8984C.jpeg
 
Are they out of the same cylinder? I ask because the ground wire on the second plug looks like it has a very lean area around the plug. Maybe. The first plug doesn’t have that.

I like the first plug better. You’ve got the idle and cruise about nailed.

Are you using ported or manifold vacuum for the vacuum advance?
 
Are they out of the same cylinder? I ask because the ground wire on the second plug looks like it has a very lean area around the plug. Maybe. The first plug doesn’t have that.

I like the first plug better. You’ve got the idle and cruise about nailed.

Are you using ported or manifold vacuum for the vacuum advance?
No they are not from same cylinder. First plug is from cyl#3 and
second plug is from cyl# 8
Using manifold vacuum
 
No they are not from same cylinder. First plug is from cyl#3 and
second plug is from cyl# 8
Using manifold vacuum
Does it need a hair more timeing ?? Second plug looks a hair bit lean . I am not an expert by any means tho !
 
Ok, here’s a couple of plugs after a 50 mile cruise yesterday. No WOT runs. I have added vacuum advance FBO billet distributor with 20* initial, 14* mechanical @3200rpm, and 12*@12” of vacuum per Dons recommendation. I think I’m really close here. What do the gurus think. 2 plugs here with 2 different heat ranges.
Plug 1

View attachment 1715550516

View attachment 1715550517

View attachment 1715550518
First plug is nice, timing is right on maybe just a hair lean on the part throttle, need more miles to make an accurate read.
Second plug is weird I would clean that one and re run it
May not have been clean when you put it in.
 
IMHO...

Run tests in the same cyl. Under as close as the same driving and outside air temperatures as you can.

Remove as many variables as you can.
 
Is there a general rule of thumb for which plug should be used for reading when the engine has a dual plane manifold? I'd imagine reading them all would provide the most info, but you're still somewhat limited by use of a carb in terms of tuning each cylinder, right?
 
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