Detonation? Plug read

[Built6spdMCSS]

Pretty sure they are DC Voltage output

 

[64nailhead]

It is beyond difficult to detect the start of knock without either a knock sensor, dyno time or track times (speed at the stripe).

For a street car, it’s always safest to find where it feels like it runs best at WOT above your ‘all in’ rpm and pull a couple of degrees back out. Reasons I say this is during normal driving there are times where the IAT’s are very much higher than during a WOT pull and the accompanying heat soak of the head. These things are typical of most every street car. Cold air intakes, a well engineered cooling system, an AFR that is NEVER lean are extremely hard to accomplish.

If and when you go to a track or dyno, it’s very easy to put the extra degree or two back in it with a timing light when you you’re trying to maximize the HP.

I’ve run plugs with and without washers on aluminum heads , SBC and LS, all of them will work, but damage will ensue if they are repeatedly over torqued. The washer is more forgiving - it’s never a bad idea to use them.

Good
Luck

Jim

 

[Baker7888]

It is beyond difficult to detect the start of knock without either a knock sensor, dyno time or track times (speed at the stripe).

For a street car, it’s always safest to find where it feels like it runs best at WOT above your ‘all in’ rpm and pull a couple of degrees back out. Reasons I say this is during normal driving there are times where the IAT’s are very much higher than during a WOT pull and the accompanying heat soak of the head. These things are typical of most every street car. Cold air intakes, a well engineered cooling system, an AFR that is NEVER lean are extremely hard to accomplish.

If and when you go to a track or dyno, it’s very easy to put the extra degree or two back in it with a timing light when you you’re trying to maximize the HP.

I’ve run plugs with and without washers on aluminum heads , SBC and LS, all of them will work, but damage will ensue if they are repeatedly over torqued. The washer is more forgiving - it’s never a bad idea to use them.

Good
Luck

Jim

I was actually debating in my head if i had some type of heat soak thing going on coming back from the long ride. I really gotta just take it out again and listen. The car seems turbulant at WOT. I guess that could be anything but i was worried it could be knock

 

[Baker7888]

For just a basic test all you need is a knock sensor, the pigtail for it and your volt ohm meter set on AC voltage.
View attachment 223981

View attachment 223982

Any sensor like that will work the only difference in them is a resistor that limits the output voltage.

Connect one lead of your meter to the pigtail and ground the other.

The voltage readings you get will increase as the vibration in the engine increases. See what voltages you get when in neutral and in first gear most of that is just noise that doesn't matter.

As you get higher voltages that's trouble. If it is really detonating the sensor is capable of like 50 volts but is limited by the resistor in the sensor. If I recall you have a 4 speed, climb a hill in too high a gear and lug the engine that should show you the "bad" voltage reading. Then you can keep advancing the timing and see where you get those same readings.

Play with it and I think you will get to understand what is damaging and what is just noise from all the parts doing their thing.

Killer idea. May have to try this. I did lug the motor and hear no knock. Yes its a 4 speed but its close ratio and the gears are pretty low and pretty tight. I know my all in is ~3200 and i cant detect a knock by ear. I know at WOT i should have No vac advance off manifold port. So by rights i Should be safe… I am tempted to drop 2 degrees but i am loving the low to mid range throttle response which is where i like to spend most of my time and dont want to sacrifice that

 

[Baker7888]

So although i dont think i was knocking (not 100% sure tho) i backed off two degrees. I am not sure if throttle response suffered or not, but WOT definitely hits harder. There is some rattle, i think its my hurst shifter. Engine is not turbulant as i previously thought.

 

[1320chevy]

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 …

Because no two engines are identical, even if built side by side. Settings are always a starting point for experimentation and fine tuning. Even older ignition systems can be modified to do far more than when they came out of the box. GM hei distributors can be made to perform as well as many race type units. Mechanical advance springs and altering the actual advance by shortening the slot as well as shimming the shaft to spec, are common mods. You can map your advance curve by using a timing light and recording timing every 500 rpm increments. Keep increasing rpm 'till there is no further advance. That's your total and the numbers you wrote down are how you got there. Small chamber aluminium heads are good for suppressing detonation and in your build, tightening up quench area is likewise helpful.
Having a "map" of your timing allows you to alter it to make it more suited to your vehicle and application. Make changes with no vacuum advance but re-attach it afterwards. (it only really affects idle but also engine temp)

 

[Ernest]

If i may.... a great way to get your ignition to play nice with your engine, is to go electronic, forsake the trial and error with weights/springs and be able to adjust on the fly via BT.

This is what im currently using with my ZZ4 - https://progressionignition.com/

 

[Built6spdMCSS]

So although i dont think i was knocking (not 100% sure tho) i backed off two degrees. I am not sure if throttle response suffered or not, but WOT definitely hits harder. There is some rattle, i think its my hurst shifter. Engine is not turbulant as i previously thought.

Some Engines don't need much timing, the better the Heads the less timing needed.