How to set timing
03-27-2008, 12:38 AM
#1
Registered User
Thread Starter
Join Date: Mar 2008
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
How to set timing Hey everyone! I'm new here, and I'm a relative noob compared to all you guys. I've been trying to read up on setting timing, but I've tried searches and I can't get an exact answer. I went on MSD's website and I saw the timing advance curves with the different spring and advance bushings. What I'm wondering is, how do you literally bump the timing up or down? The springs make it set to certain degrees, but I see you guys saying "try 36 degrees total then try 38 etc.) What I'm asking is how do you physically adjust the total timing? All I see people say is "use a light and set the timing to 36" (just an example) I don't know how to literally "set" it. I probably sound really childish so I'm sorry for that. Thanks in advance though!
03-27-2008, 03:17 AM
#2
6 & 8 Second Club
Join Date: Aug 2006
Location: Illinois, RT 66 dragway area
Posts: 2,284
Likes: 0
Received 0 Likes
on
0 Posts
.
My 2 cents. It is very very easy, & usually one of the 1st things guys learn. If you don't know how.
Get a buddy to walk you through it, or at a minimum, get a manual. You can do some major damage working on an engine if you are that clueless. Especially with only 1 post, guys might think this is a joke.
Good luck, & if you're serious, write me direct with your set up. I can give a tip or 2.
.
My 2 cents. It is very very easy, & usually one of the 1st things guys learn. If you don't know how.
Get a buddy to walk you through it, or at a minimum, get a manual. You can do some major damage working on an engine if you are that clueless. Especially with only 1 post, guys might think this is a joke.
Good luck, & if you're serious, write me direct with your set up. I can give a tip or 2.
.
03-27-2008, 12:53 PM
#3
your asking about what i think of as traditional ignition timing, you have a distributor with a rotor under the cap and no computer (or at most a little electronic module under the cap) and the mechanism by which timing is advanced is mechanical (as opposed to electronic). This is accomplished by a set of weights and springs in the distributor, if you take the cap off and the rotor off you'll see a flat metal plate preventing you from seeing down into the distributor body and shaft. Under this plate is where a pair of iron or steel weights connected by springs to the shaft sits, and these weights rotate with the shaft of the distributor along with the rotor. Hopefully you immediately recognize the fact that the faster you spin something that has a given weight (or mass) the more force it exerts outward. this is where the correct set of springs holding the weights determines what the timing advance curve (really a line) will be if you plot timing on a graph with x axis as engine rpm and y axis as amount of advance. As the engine spins faster, the weights fly outward more (depending on spring tension) but they only push out so far. This setup is physically linked to the inside shaft which the rotor sits on. And it only allows for a forward rotation of the rotor 24 degrees typically - this is 24 degrees of mechanical advance provided by the distributor. as the engine spins faster, the weights fly outward more and rotate the rotor forward in the direction it is spinning, so the rotor gets to the terminal of the distributor cap sooner, the spark reaches the spark plug sooner, and thus you have advance.
So far for what i've explained, all you can do is change the timing curve by changed out springs that hold the weights. Lighter springs will let the weights fly out sooner, or further for a given rpm so you'll have more advance. And heavier springs prevent advance till a higher rpm; lighter springs will steepen the ignition curve and heavier springs will make it less steep. But still the most advance that will be provided is 24 degrees, plus or minus depending on what the distributor was designed to provide. the typical chevy/ford v-8 distr. mechanical advance is 24 degrees.
when you set the timing, call this base timing, you disable any kind of advance mechanism whether it be mechanical or electronic. for mechanical advance, all you do is keep the rpms as low as possible which ensures the weights aren't spinning fast enough to provide any advance. This also assumes you have the correct springs and not broken springs. Typical base timing is 8 or 10 degrees BTDC. So, at rpm when the mechanical advance kicks in and provides full ignition timing advance which was 24 degrees: 10 + 24 = 34 degrees BTDC of ignition timing. So the spark plug fires at 10 dBTDC at idle and at whatever rpm and higher the distributor provides full advance the spark plug fires at 34 dBTDC.
when people talk about bumping timing to give you 36, 38, or 40 degrees of timing,
the only way you can do that with a mechanical advance distributor- because all it can [mechanically] provide is 24 degrees of advance and that cannot be changed (not even by changing springs) you have to advance your base timing setting. So if you want an extra 2 degrees of advance to give 36 dBTDC at wide open throttle, then you would have to advance the base timing setting 2 degrees to 12 dBTDC. Then when the distr. provides 24 degrees of mechanical advance, 12 + 24 = 36.
because everything is computerized these days, this info is not that common. You can just program the computer to give whatever timing you want and not even deal with a base number and an advance number, all it is is actual ignition timing.
But even for electronic ignition, where you might have a module under the cap like a pertronix, that still uses the mechanical advance mechanism built into the distributor so everything works like i described. But you can have electronic ignition modules which is basically a computer (like the MSD i believe, not that familiar with them ) which can be programmed to provide various amounts of advance at a given rpm; this still works off a base timing setting but you have the opportunity to change that 24 degree number of mechanical advance, so you could set base timing at 8-10 degrees which is where you want it at idle but can have 26 or 28 degrees of advance to get that extra 2 or 4 degrees of advance at wide open for 36 and 38 degrees of total or actual ignition timing.
So far for what i've explained, all you can do is change the timing curve by changed out springs that hold the weights. Lighter springs will let the weights fly out sooner, or further for a given rpm so you'll have more advance. And heavier springs prevent advance till a higher rpm; lighter springs will steepen the ignition curve and heavier springs will make it less steep. But still the most advance that will be provided is 24 degrees, plus or minus depending on what the distributor was designed to provide. the typical chevy/ford v-8 distr. mechanical advance is 24 degrees.
when you set the timing, call this base timing, you disable any kind of advance mechanism whether it be mechanical or electronic. for mechanical advance, all you do is keep the rpms as low as possible which ensures the weights aren't spinning fast enough to provide any advance. This also assumes you have the correct springs and not broken springs. Typical base timing is 8 or 10 degrees BTDC. So, at rpm when the mechanical advance kicks in and provides full ignition timing advance which was 24 degrees: 10 + 24 = 34 degrees BTDC of ignition timing. So the spark plug fires at 10 dBTDC at idle and at whatever rpm and higher the distributor provides full advance the spark plug fires at 34 dBTDC.
when people talk about bumping timing to give you 36, 38, or 40 degrees of timing,
the only way you can do that with a mechanical advance distributor- because all it can [mechanically] provide is 24 degrees of advance and that cannot be changed (not even by changing springs) you have to advance your base timing setting. So if you want an extra 2 degrees of advance to give 36 dBTDC at wide open throttle, then you would have to advance the base timing setting 2 degrees to 12 dBTDC. Then when the distr. provides 24 degrees of mechanical advance, 12 + 24 = 36.
because everything is computerized these days, this info is not that common. You can just program the computer to give whatever timing you want and not even deal with a base number and an advance number, all it is is actual ignition timing.
But even for electronic ignition, where you might have a module under the cap like a pertronix, that still uses the mechanical advance mechanism built into the distributor so everything works like i described. But you can have electronic ignition modules which is basically a computer (like the MSD i believe, not that familiar with them ) which can be programmed to provide various amounts of advance at a given rpm; this still works off a base timing setting but you have the opportunity to change that 24 degree number of mechanical advance, so you could set base timing at 8-10 degrees which is where you want it at idle but can have 26 or 28 degrees of advance to get that extra 2 or 4 degrees of advance at wide open for 36 and 38 degrees of total or actual ignition timing.
Last edited by 1 FMF; 03-27-2008 at 01:02 PM.
