Timing Jumping Drastically - Vintage Mustang Forums

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post #1 of 22 (permalink) Old 05-17-2017, 08:57 PM Thread Starter
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Confused Timing Jumping Drastically

Hi guys,

I have a 66 Coupe with a 1980 302 and 4 speed. Anyways, the car runs fairly well except that I have been chasing a problem with the timing for weeks now. Long story short, it turns out the PO had installed the MSD Ready to Run distributor without installing the advance limit bushing, thus the mechanical advance was adding about 36 degrees all in around 3000RPM. Not good. I have since rectified that situation with the 21 degree advance limiter bushing. So, I set my timing at 14 degrees initial, with one blue spring and a light silver one, hoping and expecting to have about 35 degrees total at 3300ish RPM. This is not the case. In reality, the timing rises with RPM as it should, until it nears 30 degrees btdc, which is when it very quickly, i.e faster than you can follow, jumps itself upwards of 40 degrees where it stays until i get disgusted and let it go back to idle. I took it out for a drive like this, and it runs like a scalded dog, better than it ever has. And so I come to you wonderful folks, has anyone ever seen anything like this before? The engine is an unknown, seems pretty stock though it does have a cam with the 351 firing order in it. I just tonight replaced the spark plug wires. The only thing that makes any sense to me is that there's something wonky with the timing chain? Though I wouldn't imagine stretch to be so abrupt and precisely at the same RPM each time, and I don't think it's slipping a tooth because it always returns right to where it belongs at idle.

Any help would be appreciated greatly,
Wylie
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post #2 of 22 (permalink) Old 05-17-2017, 10:06 PM
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Most of my stock small blocks have run 12-14 initial, with about 36 max in by 2500. I tune on a dyno so the initial can go 12+. Most peak at 32-36 total.

Grab your balancer and rotate it back and forth, simple way to check slop. * unhook the battery or disable the stater so you don't lose your limbs.
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post #3 of 22 (permalink) Old 05-17-2017, 10:12 PM
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Tongue timing

the timing chain isn't causing the issue you're having. Its in the dizzy. LSG
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post #4 of 22 (permalink) Old 05-17-2017, 10:16 PM Thread Starter
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Yeah, I am shooting for like 13-14 initial, 34-35 total. As for the balancer, its brand new and I installed it myself along with a new crank key, so I cant believe that'd be the issue, especially because its exactly the same jump each time.

Thanks,
Wylie
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post #5 of 22 (permalink) Old 05-17-2017, 10:21 PM Thread Starter
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the timing chain isn't causing the issue you're having. Its in the dizzy. LSG
I totally agree with you, but I am just wracking my brain for anything that can be causing the issue, as the distributor looks to be in perfect working order. I've checked that the weights actuate smoothly, though is it possible that there is something catching on the weights just slightly when the rotor is installed? It seems very clean to me, like new, but its a possibility that might cause this issue?
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post #6 of 22 (permalink) Old 05-17-2017, 10:29 PM
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Tongue timing

Wylie, have you considered swapping out the distributor for a DuraSpark ? MSD dizzies are made in China, and there are even fake MSD dizzies out there.....I'd get the Ford distributor if it were me. LSG
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post #7 of 22 (permalink) Old 05-17-2017, 10:36 PM
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Hi guys,
"........ I took it out for a drive like this, and it runs like a scalded dog, better than it ever has. .

Any help would be appreciated greatly,
Wylie
So the car runs great, yet you have a problem I'm not convinced the problem is in the car. It could be your timing light. Have you tried a different brand of timing light.


When the car quits running great, then you have a problem.


Z

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post #8 of 22 (permalink) Old 05-17-2017, 10:50 PM Thread Starter
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Haha Zray,

I'm the worry wart kind of a person, and with the ol' cherry bombs on full length headers its hard to tell if i'm getting and pinging. I'm planning on selling the car in the near future and would like to get everything buttoned up and ship shape for the next owner.

I have tried two different timing lights, one dial back one just an old standard one I had laying around and they both act exactly the same. I also tried hooking the inductive sensor onto a different plug wire just to see if there was any kind of cross talk with the #1 wire and it seemed to do the same thing, as there was an obvious jump.

Thanks for the help!
Wylie
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post #9 of 22 (permalink) Old 05-17-2017, 11:20 PM
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Originally Posted by WylieP View Post
In reality, the timing rises with RPM as it should, until it nears 30 degrees btdc, which is when it very quickly, i.e faster than you can follow, jumps itself upwards of 40 degrees where it stays until i get disgusted and let it go back to idle.
Does the advance "stick" at 40* and stay there until the rpm drops all the way back to idle? In other words as the rpm drops the advance doesn't also drop with the rpms? If this is true then something is hanging up in the advance mechanism inside the distributor. Are you using the vacuum advance?
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post #10 of 22 (permalink) Old 05-17-2017, 11:28 PM
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If the timing is indeed jumping up beyond the mechanical ability of the distributor, then the circuitry inside the ready to run might be at fault.

An odd problem, as a well known issue with MSD is the timing retarding at high rpm. The exact opposite of what you report.

Z

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post #11 of 22 (permalink) Old 05-17-2017, 11:38 PM Thread Starter
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Hi awhtx,

The timing does not stick at 40 until idle, sorry if my wording made it sound like that. Acutally, I can actuate the RPMs around where the 30 degree mark is and it will jump up and down from 40 to 30 and back depending on the thottle, never anything in between though.

Zra

You're right, it is a really weird problem as I have not been able to find anyone with the same issue no matter how hard I search! Haha. I have been wondering if anyone knows if you can install the advance weights upside down or backwards in some way? I checked when I was putting things back together and it seemed like there was only one way the weights fit onto the posts, but that would make some sense to me as to why something is getting stuck or the orientation of the weights could be wrong? Anyone who knows if there's more than one way the weights fit on?

Thanks again everyone,
Wylie
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post #12 of 22 (permalink) Old 05-17-2017, 11:44 PM
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Find somebody that has an old distributor machine and spin it up. Fortunately the weights are right at the top so remove the rotor and watch what happens as it spins up. If there is a mechanical problem it should be easy to see.
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post #13 of 22 (permalink) Old 05-18-2017, 12:03 AM
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Just for a test..........put some different springs in it and see if it still jumps up like that.
If it does its circuitry problems or dufus timing light(S) issues.
Let us know
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post #14 of 22 (permalink) Old 05-18-2017, 12:10 AM Thread Starter
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I'll be trying the advance weights in different orientations, if possible, and ill try stiffer springs, that's a good idea. Will report back tomorrow with results.

You guys are awesome,
Wylie
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post #15 of 22 (permalink) Old 05-18-2017, 12:14 AM
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I would send it out to be calibrated, if for nothing else, to have the data as a baseline.
Obviously, may be telling

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