92b said

You need to use the crane or fast distributor with it.

Right or wrong here is how I do it with a locked distributor. I'm assuming if it's a locked distributor it is a race car or a race car that gets driven on the street.
I start by watching the timing curve as I rev the motor through the expected rpm range. I note if or how much and where it retards in the rpm range. I start on conservative side of the expected timing and set it at the middle of the working rpm range. Example: 602 crate motor in a circle track application is 4000 to 6200 rpm. I will set timing at 5000 rpm.
I will start conservative and make the pull starting below the expected rpm range. Next I will go down 2 degrees.
It is safer to find where it looses power by going down in timing first.
Next I lay the power curves over each other and see where the power differs across the rpm range.
When laying the cuves over each other your going to see places where changing the timing a couple degrees doesn't effect it at all. Some combinations are more sensitive to timing and some are less sensitive.
Anyway, If it gains power on both ends that's easy go down 2 more degrees and pull it again. Look at the curves and compare. eventually it will loose power somewhere usually on the upper end first when going down but not always. Sometimes it will loose at both ends at once.
This is usually with a locked distributor that doesn't retard much and a motor / carb that works well. But let's say it starts loosing power on the top end and stays the same on the bottom.
Next I would drop 2 more degrees and see if the if the bottom drops. Let's say it does now I know what the bottom of my curve is.
Next if the power dropped on the high end on the first timing change. I will go up 2 from initial and see if the high end goes up. Let's say it stays the same. Now I know where the upper limit is.
I usually shoot for the least amount of timing that doesn't loose significant horsepower to keep a little cushion depending on the application and customer. Not quite enough timing might lose a little power A little too much timing might break something. If you are going to correct for all the varibles that can affect your tune then you can trim your cushion to whatever you can afford. Next I'm going to look at my power curves and see if there is a significant gain to be had that is going to justify the expense and extra maintenance of having a curve put in a distributor. If you are doing this with a computer that will probably be easier for some to do and you should have all the info you need For a starting baseline curve.
Most of my customers don't have that option. Rules don't allow. Building a timing curve that gives you what little timing advance you will need at the rpm you will need it is not as easy as it sounds and unless you are going to do it yourself you are going to have to pay someone to do it.
At some levels of competition you might have to do it to get that last little bit. If the option is to keep it locked then I might have to compromise because you can’t give it what it wants on both ends so you compromise and make it safe. I know you claim there is a lot of horsepower to be gained by unlocking every motor but my experience is different.
For example on a 602 crate you might get 4 hp. Still, not bad but for some poeple the juice isn't going to be worth the squeeze. On a 350 spec motor with a good carb and a FAST ignition system you probably wont get anything. I don't usually see the kind of power gains you talk about. Maybe we are just seeing different extremes of applications. That's a possibility.
For some of my customers simplicity and cost reign over having that last bit of power. And they are quite successful doing it that way. For others it's no holds barred.
In the end I just try to do what is going to be best for my customer considering the circumstances.

Click to expand...

92b said

You need to use the crane or fast distributor with it.

Right or wrong here is how I do it with a locked distributor. I'm assuming if it's a locked distributor it is a race car or a race car that gets driven on the street.
I start by watching the timing curve as I rev the motor through the expected rpm range. I note if or how much and where it retards in the rpm range. I start on conservative side of the expected timing and set it at the middle of the working rpm range. Example: 602 crate motor in a circle track application is 4000 to 6200 rpm. I will set timing at 5000 rpm.
I will start conservative and make the pull starting below the expected rpm range. Next I will go down 2 degrees.
It is safer to find where it looses power by going down in timing first.
Next I lay the power curves over each other and see where the power differs across the rpm range.
When laying the cuves over each other your going to see places where changing the timing a couple degrees doesn't effect it at all. Some combinations are more sensitive to timing and some are less sensitive.
Anyway, If it gains power on both ends that's easy go down 2 more degrees and pull it again. Look at the curves and compare. eventually it will loose power somewhere usually on the upper end first when going down but not always. Sometimes it will loose at both ends at once.
This is usually with a locked distributor that doesn't retard much and a motor / carb that works well. But let's say it starts loosing power on the top end and stays the same on the bottom.
Next I would drop 2 more degrees and see if the if the bottom drops. Let's say it does now I know what the bottom of my curve is.
Next if the power dropped on the high end on the first timing change. I will go up 2 from initial and see if the high end goes up. Let's say it stays the same. Now I know where the upper limit is.
I usually shoot for the least amount of timing that doesn't loose significant horsepower to keep a little cushion depending on the application and customer. Not quite enough timing might lose a little power A little too much timing might break something. If you are going to correct for all the varibles that can affect your tune then you can trim your cushion to whatever you can afford. Next I'm going to look at my power curves and see if there is a significant gain to be had that is going to justify the expense and extra maintenance of having a curve put in a distributor. If you are doing this with a computer that will probably be easier for some to do and you should have all the info you need For a starting baseline curve.
Most of my customers don't have that option. Rules don't allow. Building a timing curve that gives you what little timing advance you will need at the rpm you will need it is not as easy as it sounds and unless you are going to do it yourself you are going to have to pay someone to do it.
At some levels of competition you might have to do it to get that last little bit. If the option is to keep it locked then I might have to compromise because you can’t give it what it wants on both ends so you compromise and make it safe. I know you claim there is a lot of horsepower to be gained by unlocking every motor but my experience is different.
For example on a 602 crate you might get 4 hp. Still, not bad but for some poeple the juice isn't going to be worth the squeeze. On a 350 spec motor with a good carb and a FAST ignition system you probably wont get anything. I don't usually see the kind of power gains you talk about. Maybe we are just seeing different extremes of applications. That's a possibility.
For some of my customers simplicity and cost reign over having that last bit of power. And they are quite successful doing it that way. For others it's no holds barred.
In the end I just try to do what is going to be best for my customer considering the circumstances.

Click to expand...