Detonation? Plug read

[Baker7888]

Is this detonation?

I am looking at what appears to be black specks on the insulator. To my knowledge the ground strap looks good.

This is not a plug chop but a short burst around the block, i know that is not the right way to do it. I am not sure if i can hear audible detonation or not. Thought i might have heard something at the tail end of a long ride. I do know what it sounds like and have heard it in this car while playing with timing. I also have a pulley that is making some intermittent noise and the car is loud so its hard to tell. I lugged the car up a hill and heard nothing. It runs great. I am mostly concerned about high rpm, 3/4 throttle and above. I think i have it dialed in but considering backing off a degree or two.
Not sure if these black specks are normal or not.

 

[Baker7888]

I noticed something funny. Below is a brand new plug out of the box. Never been run. Same type. Delco R44LTS has black specks on the insulator…. I was going to install new plugs and see what happens but now i feel like that will throw my reading off …

 

[Built6spdMCSS]

I think you are way over analyzing this..

 

[Supercharged111]

White specks would be detonation.

 

[Baker7888]

Ok id just rather be safe than sorry. I would like to be done with the timing but not at the cost of a perfectly good motor. Thanks for the replies

 

[Baker7888]

I am new to reading plugs. I have found a lot of conflicting info which doesnt help. One source says ground strap color indicates timing. Mine’s up to the bend of the strap. That would indicate I am safe. I bought the new plugs to try and get a “non polluted” reading.

 

[1320chevy]

Is this detonation?

I am looking at what appears to be black specks on the insulator. To my knowledge the ground strap looks good.

This is not a plug chop but a short burst around the block, i know that is not the right way to do it. I am not sure if i can hear audible detonation or not. Thought i might have heard something at the tail end of a long ride. I do know what it sounds like and have heard it in this car while playing with timing. I also have a pulley that is making some intermittent noise and the car is loud so its hard to tell. I lugged the car up a hill and heard nothing. It runs great. I am mostly concerned about high rpm, 3/4 throttle and above. I think i have it dialed in but considering backing off a degree or two.
Not sure if these black specks are normal or not.

What we look for is the appearance of small particles of aluminium on the porcelain. That's the result of problems in the combustion chamber (piston tops). You can also check coloring of the strap or look deep down into plug and check color but that can get confusing if you have nothing to gauge it against. Best thing you can do is use a timing light, an air fuel ratio meter and tach to determine your advance rate and total timing. If you stay below 38 degrees total (36 is even safer) and your air/fuel ratio is good, it won't detonate. (assuming decent fuel octane and quality)

 

[Baker7888]

What we look for is the appearance of small particles of aluminium on the porcelain. That's the result of problems in the combustion chamber (piston tops). You can also check coloring of the strap or look deep down into plug and check color but that can get confusing if you have nothing to gauge it against. Best thing you can do is use a timing light, an air fuel ratio meter and tach to determine your advance rate and total timing. If you stay below 38 degrees total (36 is even safer) and your air/fuel ratio is good, it won't detonate. (assuming decent fuel octane and quality)

Thank you. Yes I am at 36 total. Everything has been working awesome. Thought i head detonation at the end of a cruise. I will try it again before changing anything

 

[Ernest]

I knoticed those are tapered spark plugs, im sure you are using aluminum heads, so you probably should be using the flat gasket type.

My ZZ4 is a 10:1cr with aluminum heads(non fastburn), GM specs MR43LTS plugs, tapered, just like yours, when i used those, the engine never seemed to run like i would expect it too. After a wee bit of searching around, the alternate spark plug plug is AC DELCO FR5LS, flat gasket type with 3/4"(.750) long reach like yours, since switching to those, my engine runs much smoother and better now.

As for reading plugs, im doing the same at the moment till i get my AEM WB 02 AFR gauge setup in my car, just need to find a good place to weld in my SS bung. But to the point, many have mentioned that since the use of ethenal in the gas, what you see on the plugs could be misleading, some videos on YT and other hotrod forums state that. So for now, use a little common sense, depending on the efficiency of those heads, quench area, and especially with that compression, keep using your WB 02 as your main indicator on what the engine wants, and be consevitive with your timing and listen very closely for any pinging, detonation, etc even when using at least 93octane fuel.

Btw... me thinking starting over with 28 total timing and work your way up just to be sure because of that 10.4:1 compression, im running a conservative 32 total timing @ 3000rpm with my ZZ4 engine while using a progressive ignition distributor(electronic) which makes all the difference when adjusting timing on the fly.

EDIT: https://www.enginelabs.com/engine-t...-detonation-in-high-performance-applications/

 

[Baker7888]

I knoticed those are tapered spark plugs, im sure you are using aluminum heads, so you probably should be using the flat gasket type.

My ZZ4 is a 10:1cr with aluminum heads(non fastburn), GM specs MR43LTS plugs, tapered, just like yours, when i used those, the engine never seemed to run like i would expect it too. After a wee bit of searching around, the alternate spark plug plug is AC DELCO FR5LS, flat gasket type with 3/4"(.750) long reach like yours, since switching to those, my engine runs much smoother and better now.

As for reading plugs, im doing the same at the moment till i get my AEM WB 02 AFR gauge setup in my car, just need to find a good place to weld in my SS bung. But to the point, many have mentioned that since the use of ethenal in the gas, what you see on the plugs could be misleading, some videos on YT and other hotrod forums state that. So for now, use a little common sense, depending on the efficiency of those heads, quench area, and especially with that compression, keep using your WB 02 as your main indicator on what the engine wants, and be consevitive with your timing and listen very closely for any pinging, detonation, etc even when using at least 93octane fuel.

Btw... me thinking starting over with 28 total timing and work your way up just to be sure because of that 10.4:1 compression, im running a conservative 32 total timing @ 3000rpm with my ZZ4 engine while using a progressive ignition distributor(electronic) which makes all the difference when adjusting timing on the fly.

EDIT: https://www.enginelabs.com/engine-t...-detonation-in-high-performance-applications/

Thank you for the post. Lots of info to dissect. Yes stock alum head LT1 10.4:1 this plug comes up as a stock replacement on RA. I started with NGKs and I think it likes the Delcos better to be honest. What do you mean by tapered/flat gasket? This is new to me. Found a video of a guy with LT1 carb swap on the dyno and they found 34 degrees to be the best, a 5hp loss at 36. I say this cause some will venture to say more modern heads need less timing than a SBC. I have been looking at wideband kits but have read some become overly tuned into it and also it doesnt give accurate readings in every scenario. I think this could be a distraction for me and prefer to stick to plug reading. I think i am pretty close right now, just wanna make sure i am not detonating. They talk about silent detonation and also “rattle”, does the engine actually rattle or is that just a description of the noise? My motor seems turbulant at high rpm but i need to get this hashed out before tuning the secondary. There is a lot of conflicting and maybe even misleading info out there …