Plug read, opinions needed

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H'm. Reading again, he's not saying it doesn't move. Right?
He's saying the ideal location of the line could be further up or down the strap.

There is no evidence of overheating. The line on the strap electrode that is near the weld
is sometimes interpreted by tuners to be evidence of the ideal ignition timing. The rule is
often quoted as being to adjust the timing so that the line appears in the middle of the
bend of the strap electrode. I do not agree with this theory. There is ample evidence from
improved atomization style burns that this line exists only under some conditions and I
have not been able to establish a link to the optimum timing degree. It is not as simple as
that.
 
Mattax said:
H'm. Reading again, he's not saying it doesn't move. Right?
He's saying the ideal location of the line could be further up or down the strap.

There is no evidence of overheating. The line on the strap electrode that is near the weld
is sometimes interpreted by tuners to be evidence of the ideal ignition timing. The rule is
often quoted as being to adjust the timing so that the line appears in the middle of the
bend of the strap electrode. I do not agree with this theory. There is ample evidence from
improved atomization style burns that this line exists only under some conditions and I
have not been able to establish a link to the optimum timing degree. It is not as simple as
that.
Click to expand...
You are correct. You really have to read IN to what he is saying. I’ll be reading that over and over.
 
I’ll say this, the optimal timing on this engine on this fuel, on this day, in these atmospheric conditions, correlated with the timing mark being almost all the way to the weld on the strap. How’s that for vague.
:lol:
 
Think about this:

Shrinker Total Timing and Poor Vaporization

Its all to do with the species of gasses output from the chamber. You have to look at the percentage of each species to understand why. As a burn progresses the chemicals produced go through stages until the final outcome is for a perfect burn just water and CO2. Our engines don't get to that stage but they get to the stage of producing water and CO and CO2 and a little bit of NOx and having some O2 left over. The point to consider is that it takes time to go through the stages to get to the final result.
The most important stage is the preparation prior to ignition. When that is not right, as in this engine, the flame kernel doesn't grow fast enough and the result is a lower cylinder pressure at an equivalent crank position to a good kernel. The flame kernel is a growth of laminar conditions to around 20mm diameter, then the conditions change to turbulent flame and the speed of burn is much faster. What you have to know is its droplet size and the vaporization that influences the speed of both laminar and turbulent flames. So when an engine has large droplets its needs a lot of heat to vaporize them in the time available.
When I say to you guys that a particular engine hasn't got enough vaporization that is what I'm commenting on. How it looks inside the cylinder is like this, the AFR at ignition time is leaner than the average of the cylinder, lets say the average is 12.8 but at ignition time the AFR around the plug is AFR 14, the flame is going to grow slow and some of the flames energy is going to used in vaporizing the fuel thats not gas yet. So the flame kernel doesn't generate enough heat and you dont get a TAN plug, you also run the risk of extinguishing the flame if turbulence is poorly directed. The kernel uses up about 10% of the mixture then the conditions transition to turbulent. Once the flame is turbulent it cant be extinguished. However the conditions toward the remainder of the chamber ahead of the flame kernel front are still under vaporized, therefor requiring energy from the advancing flame front to vaporize mixture ahead of the front, not an efficient way to go. It's the burn angle duration between 10 and 90% that matters. Good burns are in the range of 15 to 25 degrees. Burns of engine with poor vaporization can be as long as 45 degrees. THAT'S WHY some engines make best power at timings like 38 to 45 degrees compared to another that best at 28 degrees.

The burn time determines the peak cylinder pressure.
 
TT5.9mag said:
I addressed this comment in post 6. Unless you can substantiate this statement with fact, I will ask that you stop making it. I have two hours of dyno data running timing sweeps that suggest this engine is happy right where it’s at. Thanks
Click to expand...
Well I was under the impression that we want that burn mark on the strap further down not near the tip,please educate me you seam to know more than me.
 
Snake said:
Well I was under the impression that we want that burn mark on the strap further down not near the tip,please educate me you seam to know more than me.
Click to expand...
Read the thread in it’s entirety, we’ve been talking about it for 3 pages now. Maybe click on a few of the links that have been posted. There is a lot of valuable information being discussed here by myself and other members much smarter than I am. I do not pretend to know everything (hence this entire thread) and will not try to convince you as such. The mark on the tip of three of my plugs seems to be an indication of some type of weird chamber/burn anomaly, or maybe plug index related. The timing mark as I’ve stated multiple times is down near where the groundstap is welded to the thread base. Once again we ran timing sweeps (if you don’t know what that means please look it up) on the dyno and watched the power go away and come back on either side of 30-31 degrees. Hopefully you see this as educational and not picking you out of the group as that is not my intention. But I think there is an opportunity here for all of us to learn something.
 
Hysteric said:
Think about this:

Shrinker Total Timing and Poor Vaporization

Its all to do with the species of gasses output from the chamber. You have to look at the percentage of each species to understand why. As a burn progresses the chemicals produced go through stages until the final outcome is for a perfect burn just water and CO2. Our engines don't get to that stage but they get to the stage of producing water and CO and CO2 and a little bit of NOx and having some O2 left over. The point to consider is that it takes time to go through the stages to get to the final result.
The most important stage is the preparation prior to ignition. When that is not right, as in this engine, the flame kernel doesn't grow fast enough and the result is a lower cylinder pressure at an equivalent crank position to a good kernel. The flame kernel is a growth of laminar conditions to around 20mm diameter, then the conditions change to turbulent flame and the speed of burn is much faster. What you have to know is its droplet size and the vaporization that influences the speed of both laminar and turbulent flames. So when an engine has large droplets its needs a lot of heat to vaporize them in the time available.
When I say to you guys that a particular engine hasn't got enough vaporization that is what I'm commenting on. How it looks inside the cylinder is like this, the AFR at ignition time is leaner than the average of the cylinder, lets say the average is 12.8 but at ignition time the AFR around the plug is AFR 14, the flame is going to grow slow and some of the flames energy is going to used in vaporizing the fuel thats not gas yet. So the flame kernel doesn't generate enough heat and you dont get a TAN plug, you also run the risk of extinguishing the flame if turbulence is poorly directed. The kernel uses up about 10% of the mixture then the conditions transition to turbulent. Once the flame is turbulent it cant be extinguished. However the conditions toward the remainder of the chamber ahead of the flame kernel front are still under vaporized, therefor requiring energy from the advancing flame front to vaporize mixture ahead of the front, not an efficient way to go. It's the burn angle duration between 10 and 90% that matters. Good burns are in the range of 15 to 25 degrees. Burns of engine with poor vaporization can be as long as 45 degrees. THAT'S WHY some engines make best power at timings like 38 to 45 degrees compared to another that best at 28 degrees.

The burn time determines the peak cylinder pressure.
Click to expand...
That is interesting. It’s amazing the amount of information that can be had from examining the exhaust gasses present post combustion. Although I’m guessing my smog guy would laugh if I brought a twin turbo big block in for a smog check. This engine has a dedicated blow through CSU carb that Kevin built for it. It surprised me when he sized it at 750cfm for the power goal I gave him, and when I asked he said with the smaller 750 and the annular boosters you’ll have great response, lots of signal, and better atomization than if we used a larger throttle bore main body. Maybe he’s on to something.
 
I was about to start cutting the shells of these plugs when I realized I’m getting ahead of myself. I’m going to mark each one on the porcelain in-line with the ground strap and see where they index in relation to the intake/exhaust valves before I cut em. Hopeful that will tell us something.
 
TT5.9mag said:
I was about to start cutting the shells of these plugs when I realized I’m getting ahead of myself. I’m going to mark each one on the porcelain in-line with the ground strap and see where they index in relation to the intake/exhaust valves before I cut em. Hopeful that will tell us something.
Click to expand...

I number each plug to its corresponding cylinder so that they go back to where they came out to see what each and any change I make affects that cylinder.
 
TT5.9mag said:
That is interesting. It’s amazing the amount of information that can be had from examining the exhaust gasses present post combustion. Although I’m guessing my smog guy would laugh if I brought a twin turbo big block in for a smog check. This engine has a dedicated blow through CSU carb that Kevin built for it. It surprised me when he sized it at 750cfm for the power goal I gave him, and when I asked he said with the smaller 750 and the annular boosters you’ll have great response, lots of signal, and better atomization than if we used a larger throttle bore main body. Maybe he’s on to something.
Click to expand...

Carb sizing is relative to the engine and its ability to vaporize the fuel. Bruce said he had seen engines that need 3 inches of vacuum at WOT to make best power and others only as little as 1 inch. Vacuum plays a part in gasifying the fuel from its liquid state as liquids don't burn gasses do. He said that there were mainly 2 places to do it, one was the compression stroke by compressing the mixture (valve timing) and the other was using vacuum to do it the inlet tract. A smaller carb increases the vacuum which in turn increases vaporization of the mixture before it gets to the cylinder. Which one do you think will improve mixture distribution between cylinders?



Shrinker Intake valve closing and carb sizing:

If we look at the influence of intake valve closing point we find that at some point when the piston is coming up the compression stroke, the pressure in the cylinder will be the same as the intake runner. If we shut the valve after that point in time we have shut it too late. Once the pressure in the cylinder exceeds the intake runner the air will go back out of the cylinder. If that happens we can do something about it without tearing the engine apart, we can install a SMALLER carby. What that does is it restricts the fill of the cylinder so that the incorrect closing point of the valve is not incorrect any more. Essentially a smaller carby makes the cam appear smaller. THATS one of the factors why sometimes engines make more power with smaller carbys.
Our own drag car has had various cams ranging from 269 to 289 intake duration in it, the longer the intake duration the smaller the carbys had to be to get max power out of it. And with all the different cams its always made exactly the same power because we never changed the head flows. BUT i had to make the carbys smaller to get the power back with each successively larger cam. Every time we went larger in the cam it lost power on the old carby size.

Now read this article and ask yourself why the smaller carb ran the quickest:

How to Pick the Best Carburetor for a Street/Strip Car

By the way the 650 had 5.5 inches at WOT......
 
Last edited:
Can someone post a link that works to what Shrinker said? I thought I save a copy of several of his posts and such but I can’t find them.

I remember someone here posted pictures of their plugs and they had almost a scale pattern on the ground wire. Shrinker said a lot about that, but IIRC those plugs didn’t look anything like the OP’s plugs.
 
Hysteric said:
Carb sizing is relative to the engine and its ability to vaporize the fuel. Bruce said he had seen engines that need 3 inches of vacuum at WOT to make best power and others only as little as 1 inch. Vacuum plays a part in gasifying the fuel from its liquid state as liquids don't burn gasses do. He said that there were mainly 2 places to do it, one was the compression stroke by compressing the mixture (valve timing) and the other was using vacuum to do it the inlet tract. A smaller carb increases the vacuum which in turn increases vaporization of the mixture before it gets to the cylinder. Which one do you think will improve mixture distribution between cylinders?



Shrinker Intake valve closing and carb sizing:

If we look at the influence of intake valve closing point we find that at some point when the piston is coming up the compression stroke, the pressure in the cylinder will be the same as the intake runner. If we shut the valve after that point in time we have shut it too late. Once the pressure in the cylinder exceeds the intake runner the air will go back out of the cylinder. If that happens we can do something about it without tearing the engine apart, we can install a SMALLER carby. What that does is it restricts the fill of the cylinder so that the incorrect closing point of the valve is not incorrect any more. Essentially a smaller carby makes the cam appear smaller. THATS one of the factors why sometimes engines make more power with smaller carbys.
Our own drag car has had various cams ranging from 269 to 289 intake duration in it, the longer the intake duration the smaller the carbys had to be to get max power out of it. And with all the different cams its always made exactly the same power because we never changed the head flows. BUT i had to make the carbys smaller to get the power back with each successively larger cam. Every time we went larger in the cam it lost power on the old carby size.

Now read this article and ask yourself why the smaller carb ran the quickest:

How to Pick the Best Carburetor for a Street/Strip Car

By the way the 650 had 5.5 inches at WOT......
Click to expand...


I read the article. Obviously you know I’m going to call horse **** on that whole test. If you have 427 inches that likes a 650 over an 850 you know it’s a jacked up combination.

The cam timing was so far off it’s comical. That’s just a start.

Of course, I could be wrong. But I don’t buy the small carb nonsense because for over 40 years I’ve been proving that wrong. And by the small carb theory a tunnel ram wouldn’t make any power.

Sorry for the thread detail.

I still don’t have an explanation for what you are seeing. Only some weak theories which are really wild *** guesses.
 
Rat Bastid said:
I read the article. Obviously you know I’m going to call horse **** on that whole test. If you have 427 inches that likes a 650 over an 850 you know it’s a jacked up combination.

The cam timing was so far off it’s comical. That’s just a start.

Of course, I could be wrong. But I don’t buy the small carb nonsense because for over 40 years I’ve been proving that wrong. And by the small carb theory a tunnel ram wouldn’t make any power.

Sorry for the thread detail.

I still don’t have an explanation for what you are seeing. Only some weak theories which are really wild *** guesses.
Click to expand...
Please share your “weak theories” and “wild *** guesses”. Those are my favorite kind. Honestly I value your opinion and like to hear what you think may be going on. And if I can test some of this stuff I will.
 
Another good threads about to go down the toilet because after 40 years you're still insecure....

Go read what Shrinker said and think about it.
 
@Hysteric the motortrend carb test carries little weight because very little effort was made to even up the playing field through tuning. Look at JUST the wot afr on the tests. Even the author, Jeff Smith who is extremely knowledgeable, said many times through the article that further tuning needs to be done. I am of the opinion that shrinker is correct in saying how important vaporization is, but the tuning work has to be put in to each carb to make the results viable. Jet changes are not enough. I bet with proper tuning the larger carb on an NA 425 cube small block will be better everywhere. But not without effort.
 
TT5.9mag said:
I am of the opinion that shrinker is correct in saying how important vaporization is
Click to expand...

If a smaller carb is what it takes to get that then that's what you do. People miss the point because they are too busy thinking in absolutes instead of the thinking about what it eludes to.
 
Hysteric said:
Another good threads about to go down the toilet because after 40 years you're still insecure....

Go read what Shrinker said and think about it.
Click to expand...


Well post a link to it and I’ll read it. But if you want me to think the correct fix for incorrect cam timing is a small carb you are nuttier than a jar of goobers.

Plus, I disagree that using a smaller carb to “vaporize” fuel is the right thing to do. Getting the carb right yes. But forcing vaporization by choking air flow is *** backwards, no matter how great you think the mind is advocating for it.

Surely you can’t think I’m insecure. I post exactly what I think and how I do it. I don’t post vicariously through someone else.
 
Hysteric said:
If a smaller carb is what it takes to get that then that's what you do. People miss the point because they are too busy thinking in absolutes instead of the thinking about what it eludes to.
Click to expand...
It’s not what I would do NA. This engine is quite a bit different because I’m forcing a bunch of air down it. I believe through proper tuning, a carb with little to no restriction at wot can be tuned to vaporize the fuel correctly. But most people don’t take the time to do it.
 
TT5.9mag said:
It’s not what I would do NA. This engine is quite a bit different because I’m forcing a bunch of air down it. I believe through proper tuning, a carb with little to no restriction at wot can be tuned to vaporize the fuel correctly. But most people don’t take the time to do it.
Click to expand...

Go back and re read post 62. Bruce said what he said for a reason mainly because he could vaporize all the fuel and he did spend the time to do it to the point he developed his own platform to do it.
 
Hysteric said:
Go back and re read post 62. Bruce said what he said for a reason mainly because he could vaporize all the fuel and he did spend the time to do it to the point he developed his own platform to do it.
Click to expand...
Oh I did read it multiple times. He’s saying the exact same thing @Rat Bastid is saying. The first sentence describes the entire purpose of the smaller carb is to crutch cam timing that is closing the intake valve at the wrong point. He’s doing it just so the engine doesn’t have to come apart.
 
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