Read my plugs please
 

I have a recent build, N/A 400 sbc, about 30 hours. Was a new build from a previous motor that failed most likely due to detonation.

I installed O2 sensors in each riser and a wideband. I am currently running timing at 34 deg and my AFR readings I think/thought were pretty good. But after pulling a few plugs, I am thinking I am running lean.

SBC
Dart SHP blockhttps://cimg0.ibsrv.net/gimg/www.off...28617e81ca.jpg
https://cimg1.ibsrv.net/gimg/www.off...637d9dc39b.jpg
https://cimg2.ibsrv.net/gimg/www.off...16e72788c5.jpg
https://cimg3.ibsrv.net/gimg/www.off...31c0238d68.jpg

402 CI
JE 2618 dished pistons (9.1:1 CR)
Crower rods
Crower crank (internal balanced)
Profiler 185cc heads (Ferrea super alloy exhaust valves/comp plus intakes. Pac beehive springs)
Comp Cams (270HR-12, 218 int./224 exh. 112 LSA)
RPM Airgap
Quick Fuel 650 DP
DUI HEI distributor (Timing set at 34 btdc all in at 3k)

What are your thoughts on these plugs?

Thanks,
Jim

I know these images are pretty much useless, I was just curious if there was some indication of whats going on (besides the wide band) due to the white insulator and the white deposits.

Here are my AFR numbers before I re-jetted,
in gear:
650 (Idle) 13.2
1500 13.2
2000 13.4
3000 13.6
3600 13.9
4000 12.5
5100 WOT 12.8-13

I haven't written down my readings after the re-jet but I went up two sizes on both the primary and secondary's to get the numbers down some, which got most of the numbers down to the high 12's/low 13's. Idle out of gear is about 14. I will have to do write down some more readings on my next run. I was just concerned when I pulled those plugs and saw bright white and the deposits, haven't seen that before.

Jim

I had always heard that the dandruff on the plugs (gray specs), especially on the porcelain, is from pre ignition. A resultant of aluminum transfer.

Looks like aluminum specs all over them = detonation

looks like some sort of deposit on the plug,did it run hot?the afr,s are a little lean,i normally shoot for 12.5-1 on n/a engine.looking at piston tops with a bore scope should be the next thing you do.just curious,what fuel are you running?edit in,did you put a lot of anti seeze on the sparkplug threads when you installed them that chit detonates like a monster.

This is what they should look closer to, I took these out of my engine at the end of this year. Roughly 60 hours run and around 40 hour between 4500 to 5500 and 12:3:1 AF in that RPM range.
https://cimg6.ibsrv.net/gimg/www.off...c06d72c729.jpg
https://cimg7.ibsrv.net/gimg/www.off...e136fa114c.jpg

Sorry I don't know how to resize my pic's lol

Edit figured it out !!!!!!!!!

To read them accurately you'll need a plug reading light/tool.
https://inductionsolutions.com/shop/...-reading-tool/

Looks rich to me

Yep, way rich.

To the OP, Like was said earlier, plug readings need to be taken with a fresh set of plugs.
Run a 1/2 to mile at WOT and shut down and then read #2 and #7. They are generally the leanest running cylinders.
Next, run another mile at cruise speed around 3800 rpms and shut down and take readings.

Article with pics https://www.dragstuff.com/techarticl...ead-plugs.html

Yeah your right not the best example :) and the engine had been fogged. I was trying to show no aluminium deposit to the electrode lol

also to note are you using fuel additives ? that changes things as to what shows up on the spark plugs. Actually with the current blend of fuels plug readings really not a true guideline like the past was. I have pulled plugs out that had a full redish hue to them and its part of the fuel add packages form the fuel blenders for the reasons why . Also any blow by will show on spark plugs.

Also no anti seize on the plugs especially for reading them. I already knew this from years past especially with DIS ignitions set ups. NO anti seize period.

I talked to NGK engineers in person as I usually do when I run into them - even just currently -- one guy from Canada and one guy in WI right next to Merc / Mercruiser plants. Here is the reason why not to use anti seize and I reconfirmed exactly what I already knew.

1. the plugs already has a coating on the threads from the plug manu. NGK 4 surely does as I have been told this a 100 times by all NGK employees many years ago.
2. the anti seize changes the hot / cold range ratings of the spark plugs - that is the important issue at hand using it
3. Possible and mostly LIKELY comprising the ground path ---- spark plug to cyc head -
4. False install from tightening the plug into the head especially a false reading using a torque wrench. All the spark plug manu strongly recommend using a torque wrench for the spark plug installs.
5, Too much anti seize will have negative results for spark output 4 sure. They said they have tested that one 100 percent. And causes misfires.

anyways just passing that along again.

watch out when doing wot and then just shutting your engine off. One is water will rush up the exhaust and into the cylinders.

2 is that can be hard on the outdrive / propshaft and gears. Just saying to help prevent other issues and just incase

This is the best video I have seen

I chased my tail on my dyno reading plugs with a little too much timing. Something I thought was safe I was wrong big learning event to me.

Thats was Don Terrel of speedtalk and racing secrets. You really do not hear much about him currently like years past, I actually seen that video before and he use to sell packages on building engines and air flow , head design and so forth. Just saying. .

Like a few said looks like aluminum on plugs I would do a compression test to see where you stand. Did the motor have any blow by? And does it crank smooth or lumpy? Little scary that it blew up last time from detonation.

I read your plugs and it is not a best seller. Seems some tuning has to be done before it`s a bust .

I'm more concerned with the AFR readings than the plug pictures.

Regarding those AFRs:
Idle AFR is fine
1500 AFR is fine
2000 AFR should be closer to 13.0 vice 13.4
3000 AFR is starting to spook me. Engine has a substantial load by this time. I'd be closer to 12.8-13.0
3600 AFR is hurting the engine. I'd wager most of your damage is done here. 12.8 or richer please.
4000 AFR is ok
5100 AFR is mildly lean in my book. It should be 12.5 ish or richer.

Some of these AFR on gage could be showing false lean if its detonating.

one O2 senser on each bank is just an average of AFRs. He could have one cyc rich and one lean and so on. This is also an indication of the plugs showing rich and lean conditions.

I understand this is a carb engine but will add for whomever

efi engine fuel injectors flow rates and spray patterns play in the mix if the set of 8 plus if they are not balanced as close to possible across the board. This really holds true for used sets of fuel injectors and in many cases are commonly missed when one rebuilds their efi engine(s). That will cause rich and lean conditions alone. Just posting added info

That does not invalidate the O2 readings. Cars have had one O2 sensor per bank for years and give vital information, much more so than reading a plug. True balanced injectors are beneficial, but in this case we aren't saying one cylinder is at 17 and the others at 11.5. That just doesn't happen even with a carb. I will take the AFR readings over plugs any day assuming all else is working properly.

I believe both are valuable tools. AFR is great for tuning carb and also when permanently mounted dash gauge is a quick glance reference is to weather anything is changing in the combustion chamber. Like a warning indicator.
The AFR will tell you nothing as to detonation and heat in cylinders, this requires Plug reading (or pyrometers).
So, in my mind the two work together to give a more informed analysis of the motor health and tune.

For guys like me who dont have a mechanical uncle or anyone in the area to assist - very interesting thread. FWIW

Thanks everyone for the feedback and advice.

I thoroughly scoped each cylinder and all pistons looks good, no damage, cylinder walls look good too, I also did a compression and leak-down test and compression looks good and leak-down shows each cylinder within 2% of each other.

I reinstalled new Autolite 3924's and my plan of attack is to lower timing to 30deg (from 34deg) and take the boat for some runs to record the afr's. Then re-jet accordingly to get th afr's down etc. Then hopefully do some plug reading runs.

Thanks again

I dont like the aluminum specs on the plugs, would try to get the AFR's down in the cruise range, also might look at going colder on the plugs

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Don't change more than one variable at a time. Change jets and fatten it up before you take to the water. 34° shouldn't be the death of a NA sbc engine, richening it up should ward off detonation and get your AFR's in line. That much aluminum on spark plugs would really concern me. This isn't a 2 stroke snowmobile where you can lean it down till you start seeing aluminum on the plugs, pull the jug, swap out the piston for $75, put back together add a + size jet and be on your way.