TT5.9mag
Two atmospheres are better than one
Gentlemen the discussion was interesting and since y’all (we) were asked to leave I thought I might try to pick it back up here. Please continue.
Continuing ignition timing debate from the 416 thread.
- Thread starter TT5.9mag
- Start date
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Im not sure what difference the distributor makes. A simple points distributor doesnt retard with rpm. I can test any ignition with that.
Neither does a Unilite retard with rpm. So I have tested and qualified that the distributor doesn’t continue to retard. THEN I use the customers distributor and verify that.
92b: What I see on an engine on the dyno is that combination loses very little timing in the working range of the engine.
As for your above example, these cars you use as an example never run under caution? What about on the restart?
92b: Yes, they run under caution and they have restarts.
I know what you are doing. If the customer won’t pay for me to actually test for MBT then I do about what you do. It is what it is. But you can’t tell me that you know that at 5000 and 6000 what it needs for MBT because you can’t do that with a sweep test.
92b: why can't you use a sweep test?
Unless these cars run on a very fast 1/2 mile I never see 1200 rpm from corner exit to corner entry. And that would be down the front and back stretch. Between 1 and 2 and 3 and 4 the rpm is nowhere near that high. At least at the tracks in my area.
How do you account for that?
92b: Not sure what you mean here. I'm using a 2200 RPM working range. That is approximately where the engine would see wide open throttle under full load on dirt tracks around here. Also I'm starting the pull below that range and comparing that data. We call that restart area on the graph.
all these ignition boxes retard. If you don’t account for that you have no idea where the timing is at any given rpm.
92b: Unless I'm missunderstanding you, anyone with a timing light and a tach can see where the timing is at any given rpm.
The hard fact is the customer isn’t always right. It is THEIR a money and Im more than cognizant of that fact.
92b: Agree. I'm not always right either. Sometimes there isn't a wrong or right. And sometimes what is right for one person is not right for another. Things are not always back or white.
The truth is it’s not just the money spent for a day on the dyno. It’s general maintenance and TBO and all that adds up.
92b: What's TBO?
BTW, where is peak torque and peak power on a 602?
92b: it depends on the application. For example: 602, rochester 2bbl. and exhaust manifolds would be about 3500 pk tq 5400 pk hp. 602, 4bbl. and headers would be about 4300 pk tq 5500 pk hp. 602, rochester 2bbl and spec shorty headers would be 3800 pk tq 5500 pk hp.
Neither does a Unilite retard with rpm. So I have tested and qualified that the distributor doesn’t continue to retard. THEN I use the customers distributor and verify that.
92b: What I see on an engine on the dyno is that combination loses very little timing in the working range of the engine.
As for your above example, these cars you use as an example never run under caution? What about on the restart?
92b: Yes, they run under caution and they have restarts.
I know what you are doing. If the customer won’t pay for me to actually test for MBT then I do about what you do. It is what it is. But you can’t tell me that you know that at 5000 and 6000 what it needs for MBT because you can’t do that with a sweep test.
92b: why can't you use a sweep test?
Unless these cars run on a very fast 1/2 mile I never see 1200 rpm from corner exit to corner entry. And that would be down the front and back stretch. Between 1 and 2 and 3 and 4 the rpm is nowhere near that high. At least at the tracks in my area.
How do you account for that?
92b: Not sure what you mean here. I'm using a 2200 RPM working range. That is approximately where the engine would see wide open throttle under full load on dirt tracks around here. Also I'm starting the pull below that range and comparing that data. We call that restart area on the graph.
all these ignition boxes retard. If you don’t account for that you have no idea where the timing is at any given rpm.
92b: Unless I'm missunderstanding you, anyone with a timing light and a tach can see where the timing is at any given rpm.
The hard fact is the customer isn’t always right. It is THEIR a money and Im more than cognizant of that fact.
92b: Agree. I'm not always right either. Sometimes there isn't a wrong or right. And sometimes what is right for one person is not right for another. Things are not always back or white.
The truth is it’s not just the money spent for a day on the dyno. It’s general maintenance and TBO and all that adds up.
92b: What's TBO?
BTW, where is peak torque and peak power on a 602?
92b: it depends on the application. For example: 602, rochester 2bbl. and exhaust manifolds would be about 3500 pk tq 5400 pk hp. 602, 4bbl. and headers would be about 4300 pk tq 5500 pk hp. 602, rochester 2bbl and spec shorty headers would be 3800 pk tq 5500 pk hp.
I’m done discussing it. I can’t convince you that a curve is a good thing when it picks up power even if it’s not in the rpm range the engine runs in.
It’s a pretty simple concept. A curve can and most times will make more power everywhere.
So how is that a bad thing? You can be in race detonation and not know it, but the engine does.
If you change oil (different but the same) and the engine picks up power what does that tell you? It says the engine has less friction of several types. Even if it’s only 10 hp. Or 7 hp. That is reduced friction from somewhere in the engine.
It’s the same with a curve. I have yet to see a curve hurt power in any rpm range.
If you make a change and the engine picks up power how is that BAD? I mean WTF are you even arguing?
Discuss away but I’m done.
It’s a pretty simple concept. A curve can and most times will make more power everywhere.
So how is that a bad thing? You can be in race detonation and not know it, but the engine does.
If you change oil (different but the same) and the engine picks up power what does that tell you? It says the engine has less friction of several types. Even if it’s only 10 hp. Or 7 hp. That is reduced friction from somewhere in the engine.
It’s the same with a curve. I have yet to see a curve hurt power in any rpm range.
If you make a change and the engine picks up power how is that BAD? I mean WTF are you even arguing?
Discuss away but I’m done.
TT5.9mag
Two atmospheres are better than one
I think the main point of argument is if a curve picks up power in an rpm range that the engine will never operate in, is the juice worth the squeeze? That’s the argument I see over and over again. My problem with that is it forces guys to live with terrible manners from their engine and blame it on the big cam or carburetor when in reality a little bit of tuning, wether it be ignition curve related or fuel related can tame down some of the terrible manners and make the car much more drivable. They’re choosing to say that the engine never sees that rpm but in reality it fouls plugs in the staging lanes, or on the return road, or it has to idle at 1600rpm where with a little bit of tuning that could easily be fixed. It’s laziness and not necessarily about picking up power even though that’s what it does.
How would a locked distributor cause a motor to foul plugs in the staging lane? It would have to be either too much timing or not enough, right? Which would it be?
I agree. That’s one issue.
The other is you can NOT do a sweep test and determine what the advance needs to be at any point in the rpm range. There is no way to do it and trying to do it is a waste of time.
I have not yet had one engine with a curve that didn’t pick up power ACROSS THE BOARD. Not one. It makes more power everywhere.
I don’t know how that’s a bad thing even in a ******* drag car but evidently it is. You still have to drive the miserable pig to the starting line and back up the return road. You also have to stage the car.
But none of that matters I guess.
Two years ago I did an HEI for a buddy whose kid is doing some circle **** on dirt. He was running his **** locked out because all the hero’s and whiz bang in gym shorts types said it was the deal.
So I put a curve in it that was a wild *** guess based on some chassis dyno numbers he had, which BTW showed more power with it locked out than with the short curve he had in it.
The kid was fighting the car getting out of the corner and his restarts sucked. And it always gained temp under caution.
So I put the best curve I could get in it and had him use the vacuum advance with manifold vacuum.
The kid called and thanked me profusely for the fix. He went from a back marker to middle of the pack in three races.
The car was better off the corners, had almost no gain in temperature on cautions and he stopped getting his *** gapped on restarts.
In 2024 he was track champion. They took 25 off and they are getting ready for 26.
And my friend says at least once a race some moron comes by and tells him that VA is killing his power. Then Dan says so is the timing curve. They are killing power but we are winning.
You can’t fix stupid. I gave my **** set up so I can control the timing from the dyno bench.
When I first started doing curve testing on the dyno I didn’t have a way to change timing on the fly.
So I made a bracket with a long arm and a hose clamp and I would load the engine down, run over to the engine and rotate the distributor and watch the numbers. Then tighten it down and check the timing.
That was more than a pain in the ***.
That’s when I got out a retard box and hooked it up. Way quicker and faster. And easier.
I’ll say it again. You can’t not develop a timing curve doing sweep tests. You can raise and lower the entire curve and see the results but you can’t make a pull and say it wants less timing at peak torque and less at peak power, or if you need more timing at both or whatever.
You can’t convince people that flogging the **** out of an engine making sweeps isn’t giving the full picture. Because it doesn’t.
The other is you can NOT do a sweep test and determine what the advance needs to be at any point in the rpm range. There is no way to do it and trying to do it is a waste of time.
I have not yet had one engine with a curve that didn’t pick up power ACROSS THE BOARD. Not one. It makes more power everywhere.
I don’t know how that’s a bad thing even in a ******* drag car but evidently it is. You still have to drive the miserable pig to the starting line and back up the return road. You also have to stage the car.
But none of that matters I guess.
Two years ago I did an HEI for a buddy whose kid is doing some circle **** on dirt. He was running his **** locked out because all the hero’s and whiz bang in gym shorts types said it was the deal.
So I put a curve in it that was a wild *** guess based on some chassis dyno numbers he had, which BTW showed more power with it locked out than with the short curve he had in it.
The kid was fighting the car getting out of the corner and his restarts sucked. And it always gained temp under caution.
So I put the best curve I could get in it and had him use the vacuum advance with manifold vacuum.
The kid called and thanked me profusely for the fix. He went from a back marker to middle of the pack in three races.
The car was better off the corners, had almost no gain in temperature on cautions and he stopped getting his *** gapped on restarts.
In 2024 he was track champion. They took 25 off and they are getting ready for 26.
And my friend says at least once a race some moron comes by and tells him that VA is killing his power. Then Dan says so is the timing curve. They are killing power but we are winning.
You can’t fix stupid. I gave my **** set up so I can control the timing from the dyno bench.
When I first started doing curve testing on the dyno I didn’t have a way to change timing on the fly.
So I made a bracket with a long arm and a hose clamp and I would load the engine down, run over to the engine and rotate the distributor and watch the numbers. Then tighten it down and check the timing.
That was more than a pain in the ***.
That’s when I got out a retard box and hooked it up. Way quicker and faster. And easier.
I’ll say it again. You can’t not develop a timing curve doing sweep tests. You can raise and lower the entire curve and see the results but you can’t make a pull and say it wants less timing at peak torque and less at peak power, or if you need more timing at both or whatever.
You can’t convince people that flogging the **** out of an engine making sweeps isn’t giving the full picture. Because it doesn’t.
It can be a lot of reasons.
Too much timing down low heats the plugs. So you add fuel to cool the plugs. And it fills the exhaust ports with nasty tar.
That’s one sign.
Again, you have yet to show a single engine that wants the same timing at peak torque as it does at peak power.
You can’t because it doesn’t exist. Well, that’s not exactly true.
There are some engines that at peak power have so much mixture motion that you need to to pull some timing out at peak power.
That’s pretty rare.
You keep saying that and I keep asking you why but you won't answer. Is it information you don't want to give out? It could be something I haven't considered.
What do you look for to see that this overheating of the plug is happening. When you say down low are you talking idle speed?
MobileCustoms
You can twist perceptions, reality won't budge
Thanks for starting this thread outside of the other one.
I'm interested in making the curve on my 340/416 better and I think from what I've read in various threads, if I remember correctly, is that you don't want your timing all-in yet when your engine is in the peak torque range and want to leave a little room for more advance at higher rpm by using stiffer springs so that it can gradually add more timing once you've passed the peak torque range. And if it's true that every ignition box loses a little timing at high rpm, then the idea would be setting the max advance on the higher side, but with stiffer advance springs. Does this sound right or is my mind just mush? LOL I'm not about to argue with anyone, I just want to learn.
I know I've struggled with a little detonation in the peak torque range as well as some excess pressure in the crankcase from time to time so I think I'd benefit from stiffer advance springs at the very least. When I dial the initial timing back to assure no detonation, then It doesn't want to idle as nice. I also have my advance slots welded up pretty short to limit the amount of advance so that my initial can be 20+ which it seems to like at low rpm (I don't remember all the exact numbers right now).
OK, go ahead and laugh at me. I can take it as long as I learn something more in the end. I wish the best parts of all those threads were combined into one without all the arguing that always happens. I just want my car to perform well and more importantly, to last as long as possible. It runs pretty great but I know it could benefit from ironing a few more things out. Mine is 98% street driven but I like to have fun with it.
I appreciate the sharing of knowledge on this forum!
I'm interested in making the curve on my 340/416 better and I think from what I've read in various threads, if I remember correctly, is that you don't want your timing all-in yet when your engine is in the peak torque range and want to leave a little room for more advance at higher rpm by using stiffer springs so that it can gradually add more timing once you've passed the peak torque range. And if it's true that every ignition box loses a little timing at high rpm, then the idea would be setting the max advance on the higher side, but with stiffer advance springs. Does this sound right or is my mind just mush? LOL I'm not about to argue with anyone, I just want to learn.
I know I've struggled with a little detonation in the peak torque range as well as some excess pressure in the crankcase from time to time so I think I'd benefit from stiffer advance springs at the very least. When I dial the initial timing back to assure no detonation, then It doesn't want to idle as nice. I also have my advance slots welded up pretty short to limit the amount of advance so that my initial can be 20+ which it seems to like at low rpm (I don't remember all the exact numbers right now).
OK, go ahead and laugh at me. I can take it as long as I learn something more in the end. I wish the best parts of all those threads were combined into one without all the arguing that always happens. I just want my car to perform well and more importantly, to last as long as possible. It runs pretty great but I know it could benefit from ironing a few more things out. Mine is 98% street driven but I like to have fun with it.
I appreciate the sharing of knowledge on this forum!
Jesus. I don’t know how to say it any different than this.
You can NOT load the engine on a ******* sweep test.
Set the engine to peak torque, where ever that is and load it down and then move the timing and see what it says.
It won’t be the number you are giving it on a sweep test.
I can’t grasp why you can’t grasp this simple concept. Go do some research on MBT and learn for yourself.
And TBO is Time Between Overhaul.
That’s the last time I will say you can NOT develop a timing curve with a ******* sweep test. If you could, you could use an inertia wheel dyno and set up a curve.
BTW, my friend took his back to the same chassis dyno it was on before I did his distributor and guess what? It made more power everywhere. Across the ******* board.
The dyno operator called bullshit so he pulled a distributor he had that was locked out and dropped it in.
And guess what? The power went right back down to what it was.
The curved distributor went back in and the power went back up. And the dyno guy is still confused about the results.
I’ve talked to him. I’ve told him you can’t sweep test for timing and his thick headed dumb *** can’t grasp it.
And he still locks out any distributor that crosses his shop because he can’t do a correct curve.
So he’s sending **** out the door and calling it good.
Every box I’ve ever tested retards with rpm.
Even the exact same box with the same part number and even same manufacturing series and the ALL retard differently. All of them.
You only know what your box does if you test it.
MobileCustoms
You can twist perceptions, reality won't budge
How wide is the range of variation that you've seen? I run an MSD 6AL. I know you've put it out there in the past but that info is pretty hard to track down.
That wouldn't be the case for me. If a curve was to be added in a situation where the motor could really benefit from it it would gain at the top end of the rpm range. With a locked distributor (If it's locked I'm making the assumption it's in a racecar or a race car driven on the street) I don't want to over time the bottom end to satisfy what the top wants for max power. If I had to run a locked distributor in that case I would compromise and lose a couple horse on the top end and not over time it on the bottom where you could hurt the motor from too much timing. Just to be safe. For me the disagree is that every motor will gain big power by having a curve in it. From what I have seen some will gain a decent amount but most will gain a little bit or none at all. Depending on alot of things.
Your not telling me why. You just keep saying you can't. Only louder each time. lol. You see the difference right?
If you want to know how much your timing is retarding, lock the distributor and measure it with a timing light.
TT5.9mag
Two atmospheres are better than one
What I was saying was basically a response to what @B3422w5 wrote in his reply which I quoted above from the other thread. To answer you directly, I think it’s likely too much timing down low which keeps heat out of the chamber and out of the plug. To which they compensate with the wrong heat range, and end up loading the plug up.
MobileCustoms
You can twist perceptions, reality won't budge
I believe he's saying that you can't create a custom curve that's tailored to your peak torque range and peak HP range without having a load on it, as in having it on a dyno, no?
A hotter or cooler plug?
No, I have it loaded on a dyno when I sweep it. Thank you for trying to help.
TT5.9mag
Two atmospheres are better than one
You have a load during a sweep of course. But you’d have to make a bunch of runs with different timing numbers plugged in at a bunch of different points in the run to develop the curve and compare those runs by overlaying the graphs. If you load it steady state at one rpm (peak torque and peak hp for example) and swing the timing around while watching the observed output you could develop the curve much more effectively or maybe efficiently is the correct word.
ValiantRacing
Well-Known Member
I am always open to new ways to make power, mine and the daughter car are both drag cars, i had to put in 10 degree bushings in the dist, when they fire if i don't have 30 plus degrees of timing they wont even think about idling. They run great now! Once i put those big duration cams in, it changed everything,
TT5.9mag
Two atmospheres are better than one
The concept of ignition timing (advance) is relatively simple and it has everything to do with time. At a given rpm there is an amount of time available (necessary) for the plug to light, and the burn to happen creating the pressure in the chamber, all at the correct time to put the optimal amount of force on the piston at the correct point of rotation. Which is somewhere around 10-15 degrees after TDC. If all we had to do was account for time the curve wouldn’t be as necessary. And the ignition timing could have a relatively simple and small curve to be optimal. But we have to account for efficiency (VE) and load which has everything to do with cylinder filling and how the burn travels through a dense mixture vs a less dense mixture. At peak torque the VE (volumetric efficiency) is at its highest which means the mixture in the chamber is the most dense and cylinder pressure is higher than any other point in the rpm range. A flame moves much faster through a dense mixture than it does through a less dense mixture necessitating a lower advance value. At peak hp the mixture is much less dense and the time available for complete combustion is small so lots of advance becomes necessary. The argument is that one fixed timing advance number can cover all areas of the rpm range depending on desired use and if there is benefit to tailoring the curve to the entire range for those uses.
This is a spec. 350 2bbl motor. Fast distributor and fast box. Timing loses less than 2 degrees through the rpm range. Timing set at 5000 rpm. locked. This shows what I typically see. Notice the difference in timing requirements isn't at the peaks but rather above and below the peaks. 30 degrees of locked timing hit the sweet spot on both ends. Not saying in some cases a curve can't help. Just not in every case and the amount it helps varies. Here is a picture of the data with graphs to follow.
Edit: added graph.
Edit: added graph.
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