Distributor Over-Advancing

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mchartier105

mchartier105

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Hey all, I'm having a bit of an issue, I have a 318 magnum carbed with a new distributor and FBO limiter plate with a stock light spring and a gold FBO light spring.

The issue I'm having is that no matter where I set the plate, I get way too much advance. I had it set to 16* at first with 14* initial for a total of 30*, but when checking it with a timing light I'm getting over 50* of advance! So I tried setting the plate to 10* and kept the initial at 14* and the least I can get is about 36* of timing, which is still too much.

My question is what could possibly be causing this? I'm using an aftermarket coil and 7 pin HEI module if that makes any difference, any help is appreciated, thanks :thumbsup:
 
Are you sure your timing light is accurate?

How did the car respond to the changes?
 
Its a dial back timing light, it seems accurate, the initial doesn't jump around and when I rev it up its very linear, it pings like mad and runs crappy in the upper rpms at 50, now being at 36 seems a ton better but still pings and runs funny, so I'm guessing that what I'm seeing is accurate.
 
Do you have heavier springs you can throw in there?

Not 100% familiar with your set up, but with my MSD Pro Billet, I had to run medium springs on mine as my motor was advancing too much as well. Used to ping like crazy at 2200-2600 rpms.

Switching springs fixed it, along with throwing it on a chassis dyno to tune.
 
Gamedog said:
Do you have heavier springs you can throw in there?

Not 100% familiar with your set up, but with my MSD Pro Billet, I had to run medium springs on mine as my motor was advancing too much as well. Used to ping like crazy at 2200-2600 rpms.

Switching springs fixed it, along with throwing it on a chassis dyno to tune.
Click to expand...

What does it matter with a limiter plate? The spring should only control how fast it happens!
 
I...........do..........not........like..........."dial up".........timing............lights.

I've seen about 3 now that were off and that is enough. Recommend you scare up an old school "regular" light and check it with timing tape, or else measure around the damper calculate the advance degrees vs inches around and put a temp mark where it should be

Also you might check with TrailBeast, as I'm not "rememering" what if anything you must do with the extra pins on the HEI...........which have a timing function in the OEM installation
 
1969383S said:
What does it matter with a limiter plate? The spring should only control how fast it happens!
Click to expand...

Guess I skipped over that part.

Even then, if the timing advances too fast, wouldn't it still cause the pinging issue even with the limiter?

At least I think it did in my case...
 
No issues at part throttle cruise as I cruise around 2000rpm with the overdrive, it doesn't start going over my limit until about 3000-3500 but it just keeps on going, I stopped at 4000rpm where 50 was recorded
 
Went to a friends house last night to try his timing light, different brand, a fancy Mac one and it does the same thing, balancer is fairly new, about 4 months old, and the vacuum can is definitely not engaging, I went so far as to take the whole pickup plate out of another lean burn distributor I had without provision for a vac can and put that in my new one and it still does the same thing. I'm starting to think somehow its the coil or module
 
Does your light have provision for 2-cycle versus 4-cycle?
Does the timing advance smoothly without missed strobes or erratic screwy readings?
At what rpm does the timing advance stop, and does it consistently stop at that same rpm?
Have you plotted a graph of timing against rpm say at every 400 rpm?
 
Yes, its very smooth and linear, and it doesn't really stop advancing, I hit the 30* I should be at by about 2500 and it just keeps going from there, I personally stopped at 4000 with 50* because that was as safe as I felt going with the stock cam, there's no doubt in my mind that if I kept going further, the timing would just keep going up
 
whoa :(

50* @4000 would spell the death of the engine at full-load WOT.
But in neutral and slowly reving, I don't think it's a big deal; I have run over 60* at 2250, while rolling down the hiway.

mchartier105 said:
Its a dial back timing light, it seems accurate, the initial doesn't jump around and when I rev it up its very linear, it pings like mad and runs crappy in the upper rpms at 50, now being at 36 seems a ton better but still pings and runs funny, so I'm guessing that what I'm seeing is accurate.
Click to expand...

Oh yeah I see where I missed it.
I agree with your assessment that the light is telling the truth from the "pings like mad".
At this point I have no idea, as I have never run the HEI stuff,
but I would agree with you that the mechanical system can't do that. And I can't see the coil doing it either.
And that just leaves the ECU
 
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I more meant that 4000 is as high as I want to spin this engine with the ultra weak stock springs and baby cam, but I agree, I replaced the distributor because I thought it might be a problem with the old one I was using, but this new one has the exact same issue now so I'm at a loss. Going to try replacing both coil and module and see what happens.
 
The distributor is a stock replacement from rockauto, when I started having this issue the other day the first thing I thought was that maybe the vac can was stuck, so I pulled it out but noticed the plate had movement in it when not connected to the can, so I took the whole top plate out of a lean burn distributor with no provision for a vac can so it couldn't move at all, and used that and still had the same issue
 
I really don't see it being anything other than the module, since you have tried all these things and described the symptoms really well.
I don't have much experience with the 7 pin modules, but one thing I do know is that they are capable of making timing changes.
Seriously doubt the coil has anything to do with it, as it only fires when the ECU tells it to do so.
 
Hang on a sec;
Per post #1; with the initial set to 14*,with the plate set to 16*, you expect 30* right, but get 50. Subtracting the 14 means the system is kicking in 50 less 14, = 36*...... right?

But still at 14 idle, and resetting the plate to 10* gets you 36*. Subtracting the 14 initial, gets you 22* in the system.

So the change is not linear; In the first test 16=36, and in the second test 10=22.... or is it?
Now get this ;36/16=2.25, and 22/10=2.20
So there is a multiplier in there that is about doubling your plate advance.
Therefore it follows that if you wanted say 32 with an initial of 14*, then you would want to set the plate to 32 less 14 divide by 2.2=8
But the thing is; where will your transfer slots be at 14*?
IMO 14* initial is a tad much for a stock 5.2. So if you dialed the initial back to say 10*, then you would want to set the plate to 32 less 10 divide by 2.2=10*
So
even tho the timing looks screwy....
and is screwy......
we have this work-around.
So because of this ~2/1 correlation,I'm going with the ECU doing it.
But; that doesn't do anything for the steady march of ever-increasing timing to past 4000; that can only happen electronically, in the ECU.
So, I agree with your plan to try a different ECU.
Best of luck to you.
 
I have a set of bunch of different springs and another FBO plate to try if the module doesn't correct my problem, this is the 2nd distributor I've had with this same issue, I just got this new one recently because I figured it was my old worn out one, although the old one was only 3 years old and had about 60,000km on it (I drive my car daily)
 
Jus saying;
My D is circa 1973, And has outlived three engines. If I had to guess, I'd say pushing half a million k's, probably/ maybe more.
_________________
On a different note; Put some decent valve springs on that 5.2 and you can rev her deep in the 5's. She may not be any faster, but she will sound like she is. I did that to my Smogger-teen and shifted at 5500 all the time. First gear with 4.30s winds up pretty fast! And second with the A999/A500 trans hits 60 at about 5000, puuuurfect.
I was told that the factory 5.2 Magnum cam is a 250/264/110 but factory installed at 119 for an Ica of 64* which prevents the 9.5 engine from making a lotta cylinder pressure , and kills the effective overlap which at 37* ain't much as it is. With the screwy install the effective overlap becomes like 12*.
But if you re-time it to a 106 install, the Ica becomes 51* and the pressure jumps way way up, and the effective overlap becomes 36*; now yur talking! Retimed to straight-up or so, the stock 5.2 cam, valve-timing-wise, is actually a pretty good cam.
I don't know if what I was told is accurate, but if it is;
then with the stock cam-timing, and at a Winnipeg elevation of ~930 ft, the pressure might be
147psi@ a weak 109VP..Retimed as above,to an Ica of 51*, the pressure is predicted to rise to
166@ a very stout VP of 136.( you can do this with this factory cam cuz the intake to exhaust duration ratio is so far split; namely 14*; kindof like a Thumpr). That cam might now power-peak at 4700 rpm and with an A904, might like to be 1-2 shifted at 600 to perhaps 800 rpm higher to drop into second at 59%; or 3100 to 3250, and without a timing-computer,she'll need premium gas at WOT.
Ya know 136VP is higher than a stock 5.9 Magnum right? With the same cam,compression ratio, and stock cam-timing, the 5.9 is predicted to be
148@119VP@930 ft ....................Read about VP here; V/P Index Calculation
 
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