Timing Initial and Total

[boogerschnot]

So, Kalli's threads got me thinking about my timing and tuning. I want to get my motor up to par so Im wondering what my total timing should be and at what RPM. Ive read that between 35 and 43 total should be about right at 2500 RPM and it depends on the motor. Im at almost 11 now at idle (750-800rpm, no advance) and will probably drop that to about 9 and add a little advance with the vacuum pot for acceleration. I have noticed that I loose a little power at the top end, it used to ping barely and then i backed off timing, so im thinking that my total is still a little high, I havent checked it yet though. Also, how about the curve? Where should my timing really be kicking in at mechanically? I may need to change a spring. I get a very slight hesitation from a stop (i think its my accelerator linkage adjustment) and its strong up until Im WOT at about 80 mph where it starts to feel a little off. Its weird, it still pulls just not as hard. So does that sound about right? I found this great article on timing and it seems to be helping me out. http://www.fordmuscle.com/archives/2000/03/timing/ Thanks for help guys.

This ad is not displayed to registered or logged-in members. Register your free account today and become a member on Mustang Forums!

[kalli]

first of all you'll need a proper timing gun. one you can set from 0 to 40 or more degrees manually. there are some guns with a dial, but it's not very accurate. I have a digital one where I can set 17 or 5 or whatever I like.

I'm usually scared of too much timing especially at high rpm. So what I usually do now is to just set the gun to 36, disconnect and plug vacuum and then rev the engine to 3500. at 3500 i adjust the total (in turning the distributor) so it matches with my timing marks.
This way I have total set first. I then quickly rev past 3500 to make sure the mehanical advance is not advancing any further beyond this point.

With the total set I check on what my initial is. I try to get the initial to around 12 degrees with an alu head and 8 with iron heads. in case the car is stockish compression (9:1-10:1). Since I adjusted total, not idle I might need to change those tabs that change teh max advance.
if i want 12 initial and 34 max for example then my goal is to have a max advance of 22 degrees by the mechanical.

For the ignition curve i usually use the values that 2+2 posted. I can pull them out again if needed.
They are for a distributor dial machine, since I don't have that I multiply the advance by two as well as the rpm.
As distributor turns half the crankshaft speed. if his manual says at 1000 rpm you need 2 degrees advance that means to me at 2000 rpm at engine I need 4 degrees advance on crankshaft etc

I wonder why that FM article states: up to 42 degrees .. that sounds quite scary to me. don't really like trying that ...

I'd love to hear the other opinions, this is gonna be a good thread

PS: i'm delighted my constant stupid question posts got someone thinking :-) you'll have plenty of fun fiddling around I'm quite sure

Kalli

[boogerschnot]

Thanks Kalli,
Ive following along with your street avenger chronicles and its helping me out alot with knowing how that carb really works. Like I said It runs great but I think that with a little less total timing I could have her running like a champ. I still need to get in and see what my total is. I do have a timing gun, but its a cheapo with just a light. No special settings or anything. does the strip on my stock balancer even go up to 38 degrees? Never paid attention.


So is 3500 a better RPM for my total to be at. Or should I be at the total timing a little sooner? Im running a performer plus cam and performer intake.

What intake are you using? RPM to match the heads?

[boogerschnot]

So is the timing curve a linear curve or close to it, or does it really all depend on the motor?

Like you said, if every 2000 rpm you increase by 4 degrees? Wouldnt that leave me short of the desired total. at 2500 or 3500. Wouldnt it need to advance more?

I think im starting to nuke this one.

[eZ]

The dyno shop by my house sees almost all 302's 5.0's best at 36 total at 3,000

[67mustang302]

It completely depends on the engine setup. Chamber design, port design, plug location, VE, TE etc etc etc. Some engines with crappy chamber designs like attempts at making 5 valve heads, need 50* or more total timing because the plug is far fromt he piston, or the chamber burns poorly. Some engines make best power with only 28* total timing due to high efficiency and fast burning chambers. Some make best torque with 35 and best power with 28, so in computer apps the ECM will advance timing through peak torque, then pull timing as it approaches peak power.

[kalli]

eZ: that's good info :-)

booger: dynoshop is a great idea. i don't have one here :-)
and yes it very much depends on the motor. Compression ratio, which heads etc. Just like the FM article states: the easier it is to burn the whole load off the later the ignition has to be
This is the reason why FM state to retard ignition when low octane fuel is used, when the compression ratio goes up etc

I believe it's awlays a good place to start with 36 full at 3000. or 3000 in my case
the ignition curve does not have to be linear.

check this post: http://mustangforums.com/forum/class...ion-curve.html
2+2 has attached the stock values for the curve

for example it says for tge 12127-a:

==================================
distr rpm ---> advance in degrees
550 ---> 1.5-2.25
700 ---> 5.0-6.0
1000 ---> 6.75-7.75
1400 ---> 7.5 - 8.25
2000 ---> 8.5-10

Max advance limit 14 degrees
==================================



you can translate that to:

==================================
engine rpm ---> advance in degrees at crankshaft
1100 ---> 3.0-4.5
1400 ---> 10.0-11.0
2000 ---> 13.5-15.5
2800 ---> 15.0-16.5
4000 ---> 17.0-20.0

Max advance limit at crank 28 degrees
==================================

in the 2nd curve the recommended at 4000 is 20 degrees.
so If you have 36 total at 4000, and 20 for the advance the intial should be 16
I find that rather steep, but it says you can have up to 28 degrees

The chart for the BOSS 302 seems to work quite well, but I'm going to try as welll with 36 all in at 3000 instead of 3800-ish I have now ... who knows

In the end it's a lot of fiddling and you will need a proper timing gun so you can make sure you are not exceeding what you are planning

[my77stang]

i always here 10-12 @ idle and 36-38 total for a small block ford. seems like those are the numbers i'd be shooting for.

[boogerschnot]

Thanks guys. I can get my hands on a good gun and will try to get it going this weekend.