Spark plug reading

-
4spdragtop

4spdragtop

FABO Gold Member
FABO Gold Member
Joined
Aug 28, 2009
Messages
41,021
Reaction score
24,830
Location
Ontario Parts Unknown
Figured I would post pics(as best I could) of my spark plugs after approx 200 miles on my newly built 340. I was rechecking valve lash and figured I would post plug pics while they are out.
Hopefully to gain some insight as to fuel and timing.
**Disclaimer** plugs were new NGK BPR6ES, but the 1st 20 miles I was dealing with a lean issue and elec issues.
Specs are 340, elec ign, timing is 18* BTDC with VA plugged and disconnected.
Pics are of 2-8.
Thanks

20240813_161946.jpg


20240813_162005.jpg


20240813_162013.jpg


20240813_150339.jpg


20240813_150429.jpg


20240813_150528.jpg


20240813_150631.jpg


20240813_150720.jpg
 
Verrrrrrrrry rich. What was the lean issue? The timing mark on the ground strap is an indication of heat interpreted in relation to timing. It could lie to you until you get your AFR in line.
 
The plug almost looks too cold, you want a bit more threads on the shell showing heat. The sheen on the plug is either fuel or oil.
 
Thanks for chiming in. #2 looks oily to me, but hope not as it's new build(by me).
Lean issue was surging. Or at least I think it was a lean issue.
1405 at the time was stock rods/Jets n springs. I don't have my notes handy right now but I did a slight change (as per cal chart). I think it was springs, with little change. So I changed to 8" plain(richest) springs and 1446 rods and that solved the surging. I have since changed from 8" plain springs to 7" pink ones. Rods are still 1446(.068x.042). I have maybe 20 miles on it since last change.
Sorry for long response, trying to give as much info as possible.
Thanks!
furrystump said:
Verrrrrrrrry rich. What was the lean issue? The timing mark on the ground strap is an indication of heat interpreted in relation to timing. It could lie to you until you get your AFR in line.
Click to expand...

furrystump said:
The plug almost looks too cold, you want a bit more threads on the shell showing heat. The sheen on the plug is either fuel or oil.
Click to expand...
 
steve could it be possible your intake is sucking a small amount of oil on a few cylinders .
 
Pig rich and oil fouled. Install a new set of plugs and go make a wot run somewhere safe. Shut the engine down without a bunch of idle time, then pull a plug and have a look. Only then can you read fuel and timing.
 
I can't read them. The letters are too small.
 
Don't mean to hijack this post, but what is required to do a leak down test? Thanks
 
Thanks TT, I'll put that on the list.
Rob what #'s? Plugs are NGK BPR6ES
Thanks all.
TT5.9mag said:
Pig rich and oil fouled. Install a new set of plugs and go make a wot run somewhere safe. Shut the engine down without a bunch of idle time, then pull a plug and have a look. Only then can you read fuel and timing.
Click to expand...

RustyRatRod said:
I can't read them. The letters are too small.
Click to expand...
 
4spdragtop said:
Thanks TT, I'll put that on the list.
Rob what #'s? Plugs are NGK BPR6ES
Thanks all.
Click to expand...
The letters the little men in the cylinders write on um to tell you how the plugs are runnin.
 
[1] At idle, how much transfer slot is showing?
[2] Unless this engine is going to see WOT for minutes, not seconds [ in a boat or circle track racing ], I would using NGK 4 heat range. You will get a better idle & better mileage, & no down sides.
 
So a jump/change of 2 in heat range?
Transfer slots...I'm "pretty sure" :rolleyes: they're close to square. To be honest, I may pull carb to chk T-slots but that won't be for a week or so.
Bewy said:
[1] At idle, how much transfer slot is showing?
[2] Unless this engine is going to see WOT for minutes, not seconds [ in a boat or circle track racing ], I would using NGK 4 heat range. You will get a better idle & better mileage, & no down sides.
Click to expand...
Weak ignition is a good point. I was battling/exorcising electrical demons and there was a LOT of idle time to go with the exorcism.
Hysteric said:
Weak Ignition.
Click to expand...
 
If you look at the centre electrode and notice that it isn't clean ie no carbon on the surface facing the strap where the spark jumps across then it's clear that the ignition isn't strong enough to maintain current flow and keep it clean.

When the ignition isn't strong enough it can make it appear that it's too rich when in fact it's fine afr wise.
 
Your rings are seated, they are pretty much seated by the time you have assembled/installed/adjusted the valves etc just by turning it over by hand. Unless you have a gas ported piston and even then, they are probably seated. You can wash the cylinder walls and glaze them after you get it running and it would appear as if they never “seated”. Most failure to seat ring issues are probably more of super fat after first start up and wash the cylinder walls and glaze the bores issue. Something I did a long time ago, was weld an O2 bund in the exhaust. Then buy a cheap 2 wire O2 sensor for an old Chevy truck for like $20. Connect the leads to a cheap digital volt meter. Now this is NOT very accurate! But it will get you in the ballpark. You can search online for what afr corresponds to what voltage. I found this online

CB9CBE4B-F00B-4920-9380-6ED7D11F2E00.jpeg
 
Last edited:
Not sure what you are looking for?

Just checked the plugs today on the '89 D100 318

Stock original engine,
302 heads, stock roller cam
1406 Edelbrock 600 cfm carb

Mopar HEI conversion, E-Coil

20240816_091026.jpg


Plugs are burning perfect.

1406 600 cfm carb is a good match for stock 318s, not over rich.

HEI conversion with the E-Coil gives a much hotter spark than stock, and holds a much lower rpm idle without wanting to die.

I would say if you have good compression and a tight upper end, the mopar HEI conversion and E-coil will burn the plugs clean.

So much so they recommend another .010ths on the plug gap because the hotter spark will jump the gap.

I am running .035 ths. stock plug gap. NGK GR4 V-Power plugs.

Crazy, these plugs came installed with the truck when I bought it last Winter. And it had been sitting in a pasture for 6 years not running.

Now take into consideration that this was run on the TBI factory system with onboard computer engine management . These plugs were no where near this white, in fact they were carboned up.

Cleaned them with carb cleaner and stainless steel wire brush and re-gapped to .035 ths. and reinstalled them.

The HEI and E-coil burned them this clean after the fact.

20240816_090406.jpg


You can tell the plugs were carboned up by the carbon remains on the tip of the plug threads above.

Amazing.....

☆☆☆☆☆
 
George Jets said:
Not sure what you are looking for?

Just checked the plugs today on the '89 D100 318

Stock original engine,
302 heads, stock roller cam
1406 Edelbrock 600 cfm carb

Mopar HEI conversion, E-Coil

View attachment 1716290213

Plugs are burning perfect.

1406 600 cfm carb is a good match for stock 318s, not over rich.

HEI conversion with the E-Coil gives a much hotter spark than stock, and holds a much lower rpm idle without wanting to die.

I would say if you have good compression and a tight upper end, the mopar HEI conversion and E-coil will burn the plugs clean.

So much so they recommend another .010ths on the plug gap because the hotter spark will jump the gap.

I am running .035 ths. stock plug gap. NGK GR4 V-Power plugs.

Crazy, these plugs came installed with the truck when I bought it last Winter. And it had been sitting in a pasture for 6 years not running.

Now take into consideration that this was run on the TBI factory system with onboard computer engine management . These plugs were no where near this white, in fact they were carboned up.

Cleaned them with carb cleaner and stainless steel wire brush and re-gapped to .035 ths. and reinstalled them.

The HEI and E-coil burned them this clean after the fact.

View attachment 1716290220

You can tell the plugs were carboned up by the carbon remains on the tip of the plug threads above.

Amazing.....

☆☆☆☆☆
Click to expand...
The first plug looks good from the distance but you need to get close up photos to really be able to read them well.

1723843244354.png
 
You must log in or register to reply here.
-

Back
Top