Comments on my 340 plug under mag

[340inabbody]

Have been dealing with lots of health issues but having a strong desire to do what I can to help keep my mind off that ****.

Anyways…

Just curious what I can learn from you guys regarding your inputs on my #2 plug. Not scientific did not run it on the highway and shut it down like I should. Just around town driving with minimal carb tune. This is on my 340 with a max 32° max of timing on my Progression distributor running 92 Octane.
I was able to use my microscope to capture some pictures of the tip but just barely. Any inputs greatly appreciated!
Ron

 

[Bewy]

I would be veeeeeeeeeeery happy with that. Some might tell you that the heat range is too hot because the colour change on the ground strap is not on the bend, but I would keep using those plugs. There is an interesting discussion, & more info on plugs, on the SpeedTalk forum under ' Surface discharge plugs'.
Hope your health improves...

 

[Newbomb Turk]

You are beating it to death if I can believe your pictures.

That’s detonation.

32 degrees without an rpm is useless.

Not knowing the specifics of your engine and the the spark plug we are looking at it’s all a wild assed guess.

 

[furrystump]

This could be aluminum from detonation, but hard to say.

 

[furrystump]

and this could be a faint heat mark from timing. I cut the crimp off the plug with a cutoff wheel. Then pull the porcelain out.

 

[340inabbody]

This could be aluminum from detonation, but hard to say.

View attachment 1716401800

Yes I was wondering if that is aluminum from the piston. It is silver/gray not black like carbon. Is there a way to determine if it’s aluminum?

 

[furrystump]

hard to say, it could be just a “deposit”. Not sure of how old the plug is, other than it being pretty light in color. I don’t see any other signs of HIGH heat. The center electrode has sharp shoulders. The ground strap end has pretty sharp edges. If it was in there a while and was really hot, you could see the edges lose the crispness. What do the others look like?

 

[340inabbody]

You are beating it to death if I can believe your pictures.

That’s detonation.

32 degrees without an rpm is useless.

Not knowing the specifics of your engine and the the spark plug we are looking at it’s all a wild assed guess.

That’s what I was wondering. The specs are suspicious but I didn’t want to lead by saying anything. Been trying to lower the timing under heavy loaded conditions as I have full timing control map. This is an old problem and discussed quite a bit here ie unknown cam with fairly high compression and a non optimal torque converter. The distributor has been great to use and has solved the idle transition in and out of gear rpm differential down to like a 100 rpm. But under loaded conditions I believe I am having some detonation but with a loud exhaust it’s very hard to hear.

 

[furrystump]

Also this fuzziness could be aluminum.

 

[furrystump]

If you think it could be detonating because of other evidence. I would be more unhappy with it.

 

[340inabbody]

hard to say, it could be just a “deposit”. Not sure of how old the plug is, other than it being pretty light in color. I don’t see any other signs of HIGH heat. The center electrode has sharp shoulders. The ground strap end has pretty sharp edges. If it was in there a while and was really hot, you could see the edges lose the crispness. What do the others look like?

Thanks the plugs have low miles basically fresh. I have to pull all the plugs but the color of the deposits concerned me but I am not experienced in seeing many plugs. The specs are not black but silver in color like aluminum?
I will look at all the plugs today and report back.

 

[furrystump]

Getting more concerned, that is a good bit of deposits for a new plug. Not fuel trim, just stuff on it.

 

[Oldmanmopar]

Looks Lean on the high speed side. Are you running an air cleaner? If you are that is probably aluminum. Looks like plugs pulled from a dirt track engine.

 

[340inabbody]

Looks Lean on the high speed side. Are you running an air cleaner? If you are that is probably aluminum. Looks like plugs pulled from a dirt track engine.

Yes run as shown in first picture.

 

[Inertia]

If you can get a bore scope in there, detonation damage on the piston will begin, or be more evident on the piston outer edge, opposite side from the spark plug.
Good luck

 

[Newbomb Turk]

You need to cut the plug apart and post a picture of just the porcelain.

I forgot this is a bit of an unknown on cam timing and such.

Like I said, if I can believe your pictures (not getting fooled by lighting and angles) that IS detonation.

If you are running the engine cold, like 160 degrees and you haven’t done what needs to be done to get the fuel vaporized in time, and if you have a cold air intake you can easily get into detonation no matter what you do for timing.

At that point you either need to address the fuel vaporization issue by as many remedies as you have to so you can get rid of that detonation.

If you have a carb you need annular boosters. Especially if you have a cold air intake.

Burr finish the intake manifold. You’d be surprised what that does.

Run the engine temperature to 190-200. I absolutely do not like doing that but if it comes down to a hot engine and no detonation and a cold engine that’s rattling its guts out I run them hot.

Also, I know you said you have 32 degrees of timing but at what rpm?

32 at 2500 or even 3000 rpm in a detonation sensitive engine is probably too much.

As a test, you can add a TON of of fuel so that you increase the chances of making sure all the air molecules have fuel around them in high enough volume it doesn’t rattle.

Of course, fuel consumption takes a massive dump and low speed drivability takes a big hit but you won’t be knocking the rings and bearings out of it.

Edit: I forgot to mention you can’t always hear it.

Most likely it’s detonating at and around peak torque and not at WOT.

They almost never rattle at WOT because your VE is much lower than at peak torque so the chance of detonating is far less.

That’s why I always say this and I k ow I’m being redundant but engines want less timing at peak torque and more timing at peak power.

It follows the VE curve.

I don’t know your rpm but peak torque is somewhere between 1500-2000 rpm less than peak power.

So if you have peak power at day 6500 that means peak torque will be between 4500-5000 rpm.

If you are at max timing at or before that rpm (whatever that rpm is based on your engine and not my example) you need to correct that.

 

[TT5.9mag]

Who cares what the total timing is. What is the timing at peak torque? That plug shows signs of distress for sure, but it ain’t the total timing that’s causing it. And with no full throttle, full load pulls reading the plug for fueling is useless. Looking at the plug, it’s detonating, it’s cold, and the total timing is a degree short of perfect. You need to work on the CURVE and get the timing out of it when it’s rattling. You might need to move to more octane in the short term just to keep it alive.

 

[Newbomb Turk]

Who cares what the total timing is. What is the timing at peak torque? That plug shows signs of distress for sure, but it ain’t the total timing that’s causing it. And with no full throttle, full load pulls reading the plug for fueling is useless. Looking at the plug, it’s detonating, it’s cold, and the total timing is a degree short of perfect. You need to work on the CURVE and get the timing out of it when it’s rattling. You might need to move to more octane in the short term just to keep it alive.

lol that’s what I was saying but you said it better.

 

[Killer6]

lol that’s what I was saying but you said it better.

Caught channeling Your inner AJ again,.......lol...

 

[340inabbody]

You need to cut the plug apart and post a picture of just the porcelain.

I forgot this is a bit of an unknown on cam timing and such.

Like I said, if I can believe your pictures (not getting fooled by lighting and angles) that IS detonation.

If you are running the engine cold, like 160 degrees and you haven’t done what needs to be done to get the fuel vaporized in time, and if you have a cold air intake you can easily get into detonation no matter what you do for timing.

At that point you either need to address the fuel vaporization issue by as many remedies as you have to so you can get rid of that detonation.

If you have a carb you need annular boosters. Especially if you have a cold air intake.

Burr finish the intake manifold. You’d be surprised what that does.

Run the engine temperature to 190-200. I absolutely do not like doing that but if it comes down to a hot engine and no detonation and a cold engine that’s rattling its guts out I run them hot.

Also, I know you said you have 32 degrees of timing but at what rpm?

32 at 2500 or even 3000 rpm in a detonation sensitive engine is probably too much.

As a test, you can add a TON of of fuel so that you increase the chances of making sure all the air molecules have fuel around them in high enough volume it doesn’t rattle.

Of course, fuel consumption takes a massive dump and low speed drivability takes a big hit but you won’t be knocking the rings and bearings out of it.

Edit: I forgot to mention you can’t always hear it.

Most likely it’s detonating at and around peak torque and not at WOT.

They almost never rattle at WOT because your VE is much lower than at peak torque so the chance of detonating is far less.

That’s why I always say this and I k ow I’m being redundant but engines want less timing at peak torque and more timing at peak power.

It follows the VE curve.

I don’t know your rpm but peak torque is somewhere between 1500-2000 rpm less than peak power.

So if you have peak power at day 6500 that means peak torque will be between 4500-5000 rpm.

If you are at max timing at or before that rpm (whatever that rpm is based on your engine and not my example) you need to correct that.

Thank you again for taking the time to explain this to me. I am digesting your response as well as others here. Αctually I AM running a colder 160° thermostat. I had thought bringing the temp down would help alleviate detonation. I get what your saying about colder temps making atomization more difficult. I will try a 190° T- Stat as well as what ever else I can try mechanically. I will also post my timing map.

I suppose I cannot retrofit annular boosters to a 4150 style Holley?

Here’s what the ceramic looks like on my Autolite 65.

 

[Newbomb Turk]

Thank you again for taking the time to explain this to me. I am digesting your response as well as others here. So I actually I AM running a colder 160° thermostat. I had thought bringing the temp down would help alleviate detonation. I get what your saying about colder temps making atomization more difficult. I will try a 190° T- Stat as well as what ever else I can try mechanically. I will also post my timing map.

I suppose I cannot retrofit annular boosters to a 4150 style Holley?

Here’s what the ceramic looks like on my Autolite 65.

View attachment 1716402101

You are very fat at WOT. That big black carbon ring should be between .125 and .187 on pump gas.

Race gas can get down to about .080but if the weather changes quickly and you can’t make a jet change you’ll be into detonation.

Even I don’t like tuning that close to the edge.


You can change the booster in a 4150 Holley if you have the tool. I bought the tool because I just almost never use downlegs any more.

You are correct that 160 coolant temperature will reduce detonation but as you are finding you just can’t drop the temperature.

Todays pump fuel is is EFI formulated so it’s even tougher to get it vaporized without some heat or a good booster.

I forget is your intake a cold air manifold?

 

[340inabbody]

You are very fat at WOT. That big black carbon ring should be between .125 and .187 on pump gas.

Race gas can get down to about .080but if the weather changes quickly and you can’t make a jet change you’ll be into detonation.

Even I don’t like tuning that close to the edge.


You can change the booster in a 4150 Holley if you have the tool. I bought the tool because I just almost never use downlegs any more.

You are correct that 160 coolant temperature will reduce detonation but as you are finding you just can’t drop the temperature.

Todays pump fuel is is EFI formulated so it’s even tougher to get it vaporized without some heat or a good booster.

I forget is your intake a cold air manifold?

It’s the Chinese Air Gap don’t know what a cold air manifold actually is.

 

[Newbomb Turk]

It’s the Chinese Air Gap don’t know what a cold air manifold actually is.

View attachment 1716402151

That’s a cold air intake.

It has no provision for exhaust heat cross over AND it has an air gap between the plenum.

If you look at a Performer it has a heat cross over and no air gap.

 

[340inabbody]

That’s a cold air intake.

It has no provision for exhaust heat cross over AND it has an air gap between the plenum.

If you look at a Performer it has a heat cross over and no air gap.

I live in AZ it will be 120°F soon lol oh and that tool is almost as much as a carb! I doubt I would use it more than once…

 

[Newbomb Turk]

If you buy the boosters and send me the carb I’ll install the boosters for you.

Just call Mark at Lightning Racing Carbs in Florida and get his boosters and banjo’s.

His are by far the best booster out there.

Let me know if you want to do it.