Sparkplug detonation signs?

[Truckedup]

This plug is from my vintage Triumph 750 street bike...It does look like this real life, I'm looking at the very faint spots on the insulator, wondering if they are signs of detonation...The plug was pulled after a run in cool weather at high power loading, 75 percent throttle or more in high gear for about 10 miles. It was not a clean plug chop, the bike was backed down to normal road speed and then the plug inspected..The fuel is 90 octane non ethanol pump gas. The plug is a NGK Competition #7 , this type engine normally runs a #6...What goes on, I modified the engine for tight quench, increased intake port velocity to deal with lower octane fuel..Typically these engine will ping on anything less than 93 octane..The total timing is the stock 38 degrees, I may want to retard it a few to see if it affect performance

[ClassAct]

It's hard to tell from a picture and not being able to rotate the plug and use a quality magnifier so you can see all the way down the shell, but I'm not seeing anything that would worry me. You may be a tick short on total timing, but I doubt a degree or two more total would show any power.

What ignition are you using? It almost looks a bit like the ignition is on the weak side.

Just what I can see from a picture.

[Truckedup]

It's hard to tell from a picture and not being able to rotate the plug and use a quality magnifier so you can see all the way down the shell, but I'm not seeing anything that would worry me. You may be a tick short on total timing, but I doubt a degree or two more total would show any power.

What ignition are you using? It almost looks a bit like the ignition is on the weak side.

Just what I can see from a picture.

The ignition is a 45 year old Lucas Rita electronic..it is modified to produce a bit more energy and a few new parts, Waste spark with two typical motorcycle canister coils wired in series..It might be a bit feeble but there's not too many options other than a $500 type I use in my vintage race bikes..

[ClassAct]

It's hard to tell from a picture and not being able to rotate the plug and use a quality magnifier so you can see all the way down the shell, but I'm not seeing anything that would worry me. You may be a tick short on total timing, but I doubt a degree or two more total would show any power.

What ignition are you using? It almost looks a bit like the ignition is on the weak side.

Just what I can see from a picture.

The ignition is a 45 year old Lucas Rita electronic..it is modified to produce a bit more energy and a few new parts, Waste spark with two typical motorcycle canister coils wired in series..It might be a bit feeble but there's not too many options other than a $500 type I use in my vintage race bikes..

That's ok. I see nothing alarming. Others should chime in. It's not like the ignition looks like it has a serious misfire issue. You may try a fine wire plug and see what happens. We know that there is a certain percentage of misfires no matter what you do. Decreasing misfires is always a power booster. Sometimes you can only do what you can do.

[ClassAct]

I forgot to mention that when you don't cut the engine clean you can see a bit of clouding in the plug. It's just like driving a car back up the return road and reading plugs. I ignore the fogging or clouding or whatever you want to call it. When I get the tune up to the point I think I'm close, then I tell the customer to clean cut the engine and they either tow it back or my fat arse gets a ride down to the other end and we look at the plugs. No way am I walking that far. Not even for a track dog and a Dr. Pepper.

[engineguyBill]

The first signs of detonation will be small round deposits of aluminum piston material on the plug's insulator. These deposits are hard to see, but can be identified by using a lighted, magnified spark plug viewer.

[Truckedup]

The first signs of detonation will be small round deposits of aluminum piston material on the plug's insulator. These deposits are hard to see, but can be identified by using a lighted, magnified spark plug viewer.

Yes,looking at the plug with a bright light and magnifying glass it's not clear if there are any or not..I'm borrowing a freind's medical otoscope to have a better look.

[mag2555]

Aluminum Piston material transfered to the plugs ciramic cone due to detonation looks like shiny purple / Aluminum balls under a mag glass.
It's hard to tell since the plug is showing color, but that heat range maybe too cold.

[Truckedup]

The normal heat range for this engine stock is #6 NGK conventional plug...The plug you see is a #7 competition, it has a shorter ground strap..
These are old style deep hemi combustion chambers with around 8.5 actual static compression that are prone to detonation on 93 octane pump gas unless tuned carefully.....On this engine I milled the cylinder to close up what quench there is to .032..retarded the intake cam lobe center line to 100 degrees.The=is later cylinder head(1979) has more turbulence...The actual static compression is 9.15-1....I'm running it on non ethanol 90 octane pump gas that's easy to find around here..The engine appears to have more power and better throttle response than stock...

[dorset]

more pitchers, please

[Truckedup]

more pitchers, please

Well, you're the guy that knocked me off the bike class land speed racing throne, I'll give nothing, I'll see if I can get a better photo with different camera

[dorset]

moi?

how can i keep up with what you're doing if you don't post more pitchers? look, here's me

[In-Tech]

Haha, good pic,
Put the plug in a lathe and take off the threaded part, makes it much easier to inspect.

[af2]

Haha, good pic,
Put the plug in a lathe and take off the threaded part, makes it much easier to inspect.

Carl? The strap looks un touched.......?

[In-Tech]

Hi Adam,
Everything is soooo hard to tell in a pic. Detonation and preignition is uncontrolled combustion and sometime just looking at the porcelain all the way up near the curve when it meets the main ground body will show some things. Sometimes not.

I still need to cut open the 8 spark plugs from the last engine on the dyno, 1428hp on 91 octane. I didn't get to do individual cylinder trim since when I went to the dyno the next monday it was off and in the back of the truck.

I haven't looked at individual AFR or EGT yet so I will soon and compare to the cutaway of the plugs when I am done and I'll start a post about what I see or don't

Chances are it will be going back on the pump so I can finish.