Need some help with my timing curve.

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75slant6

75slant6

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So after running an eBay Ready-to-Run Hei distributor for the past 5-6 years, I finally got around to putting a timing light on it and mapping out the advance curve. Come to find out, the curve was severely lacking! I ended up swapping out that distributor with a factory electronic distributor that I left the factory light spring in it and swapped out the heavy long looped spring with a black spring from the Fbo spring kit.
Here are the two curves laid over a graph that I saw @Mattax post on here a few times.
The R2R curve starts at 18 initial, overlaps the new distributors curve between 1500-1750, then goes to 20-21 at 2000rpm. The new curve is obviously much better but could still be improved. What step would y’all take next to optimize the curve some more?

Btw, this is on a bone stock 5.9 magnum running a China-gap intake and a 1405 carb and a manual transmission.

700510BD-00DC-4E32-90B2-A015566232E1.jpeg
 
75slant6 said:
What step would y’all take next to optimize the curve some more?
Click to expand...
Black spring you put in placing tension on the weight with the governer installed?
If so, put the stock spring back in.
Run it.
Then adjust the spring perches to control the initial tension and degrees out before the secondary spring adds tension.
 
I’ve found that bone stock 5.9s don’t need anywhere near 36 degrees of total. In fact if you watch Richard Holdeners 5.9 testing on you tube he says his made best power around 27 degrees. I think I settled around 30 for mine. +-1 deg. They make peak torque around 3200 so I’d delay the all in till about that point. I like your 16 degrees initial and I’d build a curve with two stages. Bring in like 8 degrees pretty quickly with a light spring and use a little heavier one to add 6 or so more after peak torque.
 
^^That's^^ more specific advice than I could give for a 5.9 not having messed with them.
The target range I posted in those other threads was specific to the person's application.
The shape of the MP small block advance is generally about right for a 4 bbl LA engine w/ a 4 bbl cam, or somwhat hotter aftermarket cam. etc.
A more efficient burn under load, for whatever reason, in any part of the rpm range would reduce the lead time needed at that rpm. That could be more efficient heads under high flow conditions (less timing at higher rpms), it could be more heat in the upper part of the cylinders and combustion chamber, etc etc.

Only thing I would add to TT5.9mag's guidance is that there is rarely a reason to hard stop the advance at 2800 or 3000 rpm as long as its advancing slow enough.
The various long looped heavy springs Chrysler distributors came with is the secret to the two stage advance that creates a curve like the one in the MP distributor I plotted out.
 
I completely agree with you @Mattax but in stock form (cam/springs and heads) the 5.9s are just about finished making any kind of power around 4800rpm so in my experience working much more on the curve is a wasted effort. Now add a cam and some springs and do a litttle head work and it’s a whole new ball game.
 
And as long as you delay the rate rate of advance around that peak tq number you’re correct. You can’t really ever hard stop the advance as long as the engine is accelerating but you do need to slow it down. And if you get it right it’ll run on junk 87 octane with no problem.
 
54064C7E-0426-49A0-B69D-B077531F4835.png

This is the mopar performance aftermarket ecu timing table. Just fyi
 
Mattax said:
Black spring you put in placing tension on the weight with the governer installed?
If so, put the stock spring back in.
Run it.
Then adjust the spring perches to control the initial tension and degrees out before the secondary spring adds tension.
Click to expand...
Yeah the black spring I put in puts tension on the weight when the t-handle thingy is installed. So basically, pull that black spring back out and put in the long loop spring and remap it and see where it’s at?
 
TT5.9mag said:
I’ve found that bone stock 5.9s don’t need anywhere near 36 degrees of total. In fact if you watch Richard Holdeners 5.9 testing on you tube he says his made best power around 27 degrees. I think I settled around 30 for mine. +-1 deg. They make peak torque around 3200 so I’d delay the all in till about that point. I like your 16 degrees initial and I’d build a curve with two stages. Bring in like 8 degrees pretty quickly with a light spring and use a little heavier one to add 6 or so more after peak torque.
Click to expand...
I did install an Fbo limiter plate as well, I currently have it set to 18, so 16+18=34. Would you recommend setting it to 12-14 instead for a total of 30-32?

Now, to throw a wrench in all of this… I do have speedmaster heads and a bigger cam that I’ll be installing hopefully this year sometime, but I can always recurve it again at that point
 
75slant6 said:
I did install an Fbo limiter plate as well, I currently have it set to 18, so 16+18=34. Would you recommend setting it to 12-14 instead for a total of 30-32?

Now, to throw a wrench in all of this… I do have speedmaster heads and a bigger cam that I’ll be installing hopefully this year sometime, but I can always recurve it again at that point
Click to expand...
I don’t think 34 will make any more power than 29-30 it will just make it more prone to detonation. But I also wouldn’t move too far away from 16 initial. So it’s hard to tell you what to do with the FBO plate if those are your only options. I make my timing what I want it to be. I don’t settle on what FBO or mopar or MSD or anyone else give me. If that involves welding and grinding on the plate then that’s what I do. If you’re changing the program up with heads/cam ect I would definitely tune that combo independently of this one. The heads will likely want a different curve and they definitely will want a different total amount from what I’ve read. I haven't used those heads.
 
75slant6 said:
Yeah the black spring I put in puts tension on the weight when the t-handle thingy is installed. So basically, pull that black spring back out and put in the long loop spring and remap it and see where it’s at?
Click to expand...
Yes.
75slant6 said:
I did install an Fbo limiter plate as well, I currently have it set to 18, so 16+18=34. Would you recommend setting it to 12-14 instead for a total of 30-32?
Click to expand...
I'd leave the plate out. (See TTI's posts 6 and 7 together. More on this next post.)

First see how many degrees out the heavy spring engages.
Note: You can actually eyeball that. Note the distributor degrees stamped on the governer plate. Double that for crank degrees.
With the long loop spring installed and the governal plate installed. Use a small pry bar (blunt brake adjuster, whatever is convenient) to move the weights. See how far it moves before that slong loop contacts and adds tension. Lets say it engages about 1/2 way up the slot and its 26* governer (stamped 13). In that case it will slow down the advance roughly 13* above initial.
You can tweak it a little by rotating the spring perches.
75slant6 said:
Now, to throw a wrench in all of this… I do have speedmaster heads and a bigger cam that I’ll be installing hopefully this year sometime, but I can always recurve it again at that point
Click to expand...
 
That timing table is great to see. I'll have to look later at Richard Holdener's vid that you reference.
At the drag strip, or even on a dyno, a little more timing can pick up some power because the engine isn't heat soaked like it gets on a long trip or road racing, etc.
I think with the distributor, unless using an ECU with some predictive ability, we can count on losing a degree or two every 1000 rpm increase. That's another reason I don't like the hard stop.
I completely agree that it may be that the advance limiter plate may be useful if the situation warrants. Testing with the plate installed we may not get to learn the characteristics of this long spring/advance slot combination.

In sum I think we are in complete agreement, just looking at it from different perspectives.
 
You've prob seen these but if not, I kindof spill the beans on shaping the curve here and with Rick as he works through and posts the effects of his changes here.
 
@Mattax, You provide a hell of a lot of valuable information here for everyone. Thank you. The two threads above should be made stickies. I hope guys listen when you talk.
 
Another photo that may prove useful. This is a superchips flash tune for 93 octane for a stock 5.9.
FFAD7E84-98EF-4490-A8BF-D923E0DE1D16.png
 
My governor is stamped 15L so would that make it add 30 degrees mechanical? So maybe I should run the Fbo plate (same as welding up the slots)?
 
Ok, so I left the Fbo plate in but I installed it to allow 14* degrees mechanical for a total of 30*. I removed the black spring that I had installed and reinstalled the long looped factory spring like mattax had suggested. Here’s my new curve. It jumped from 16* at 1000rpm to 22* at 1250, so I took a reading at 1100 and 1160 to get a more accurate graph of how the curve is going.

image.jpg

I drove the car to work this morning with yesterdays curve and it was easy to tell it wanted timing sooner, it would buck and surge at low rpm but once the timing came in around 1750-2000rpm it wanted to GO! I got a small taste of how the Honda boyz feel when the V-Tec kicks in!
:rofl:
I test drove the car this afternoon after changing the curve it what it currently is, and it’s definitely better down low. Still feels like it might want a touch more, so I might see about bumping the initial up to 17-18 and see what that does. The car definitely has more power than it’s ever had! I also hooked up the v-can and didn’t get any detonation pulling hills in 5th gear, hopefully I’ll also get better fuel mileage than ever before. I can now pull, recurve and reinstall my distributor in 30-40 minutes, so if y’all have any more tips/suggestions, I’m all ears!
 
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Map out what your vacuum advance is doing also if you can. There is mileage to gain. It might like 45 or so degrees at cruise. And you might try to bump one or two degrees in to the top as mattax suggested just to see if it likes it and differs from dyno to car. Oh and get a new set of plugs, rip it once, shut it off and pull em. Let’s see what the timing mark and fueling look like.
 
TT5.9mag said:
Map out what your vacuum advance is doing also if you can. There is mileage to gain. It might like 45 or so degrees at cruise. And you might try to bump one or two degrees in to the top as mattax suggested just to see if it likes it and differs from dyno to car. Oh and get a new set of plugs, rip it once, shut it off and pull em. Let’s see what the timing mark and fueling look like.
Click to expand...
I’ll have to research how to map the vacuum advance. I do have a new set of plugs to put in. By “rip it once” do you mean install, start the car, rev it up, shut it down? Or take it for a short rip on the street?
 
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