[Verdoro 68]

Here’s a weird one…

I’m seeing my timing bounce 8-12 degrees retarded and back to the specified timing at idle with a dial back light. The RPMs on the timing light tach randomly toggles between 800 and 1400 - but the engine itself is not changing RPM. Idle is steady and smooth as is vacuum. It sounds healthy and runs great. The timing is steady once I put some RPMs into it.

My first thought was timing chain slop. It’s a new Rollmaster with under a thousand miles on it. I just put the engine back together a couple weeks ago and there wasn’t any slop that concerned me. The fact that the engine sounds and idles smooth while the timing light is freaking out makes me think it’s something else.

I tried 4 different timing lights all with the same results. I was seeing the timing bounce with all of them and RPMs toggle whether the light was on plug 1 or plug 3. Distributor was recently reworked by SunTuned so I know it's set up right. New BOP distributor gear that doesn’t show any abnormal wear. Checked for vacuum leaks and didn’t find any.

I’m wondering if this could be an ignition system issue. Rotor and cap are new. Pertronix Ignitor and coil are also new, but we know they don’t have the best reputation. Taylor plug wires are also new. I have an extra Pertronix I may try swapping in first. Any other ideas? The car runs strong otherwise!

[JLMounce]

What's the cam endplay? These things will typically still run pretty good even with a good amount of cam endplay, but the wider that is, the more movement (especially if it's a roller with non tapered lobes) you'll see. As the cam moves back and forth, the mesh of the distributor gear to the cam gear changes and will effect timing as it does so.

[mgarblik]

As much as I hate to admit it, that sounds like a Petronix glitch. I personally haven't had any issues with them, but many, many people on this forum have had multiple failures. Petronix is a Chinese, electronic product, so that is the first place I would go. If you just had jumping timing, I would look at weak dist springs, loose rotor tab, something like that. But the RPM indicated change indicates a signal problem to or out of the module.

[Verdoro 68]

Cam end play is .002 which is a little on the tight side. If I turn the engine by hand I there doesn't appear to be any lag in the distributor rotation either forward or backwards so that makes me think the timing chain is ok.

My hunch about the ignition system appears to have some legs. I swapped out the Pertronix module, cap and rotor but the issue persisted. Then I tried another old Taylor Spiro pro wire I had laying around on the #1 cylinder. The issue persisted. Out of curiosity, I swapped in a date coded reproduction 'Lectric Limited plug wire for #1 and the timing normalized!

Here's what I was seeing with the Taylor wire: https://www.youtube.com/shorts/rwXpzN0E-yk

And here's what it looks like with the Lectric Limited: https://www.youtube.com/watch?v=GyTZmqnqeMk

I wonder what it is about the Taylor wires that could be causing this?

[steve25]

Is the voltage output of your Alt steady below 2000 rpm?
Judge this by a hand held meter, not one you may have in the cars dash.

[Verdoro 68]

Great question - I haven't checked the alternator!

[Gator67]

So swapping out the Taylor #1 ignition wire solved the problem? If so, I wonder if that wire was causing an issue with your timing light?

[dataway]

I was recently adjusting my timing and noticed it would jump all over the place if the distributor hold down wasn't tight. I had it snug, just loose enough that I could nudge it by hand but by no means "loose". I was very surprised that the difference between snug and tight made that much of a difference in timing stability. I guess it also could have been the distributor loosing a proper ground through he hold down clamp.

Nevermind .... I see you found the issue.

Is the Spirowire an EMF shielding wire? A spiral winding might play heck with an inductive clamp.

[mgarblik]

Make sure you have 12Volts + to the ignition coil. Pertronix will not run correctly through a ballast resistor or the factory resistance wire in a points car. Glad you have it figured out.

[Verdoro 68]

Originally Posted by Gator67

So swapping out the Taylor #1 ignition wire solved the problem? If so, I wonder if that wire was causing an issue with your timing light?

Originally Posted by dataway

Is the Spirowire an EMF shielding wire? A spiral winding might play heck with an inductive clamp.

These are Taylor Spiro Pro which I've used for years, just a new set.

I think it's the Taylor wires in general. I did a direct comparison on multiple wires and the timing is steady with the Lectric wires and bounces with the Taylors which is weird because lots of folks use Taylor without issue (me included).

Originally Posted by mgarblik

Make sure you have 12Volts + to the ignition coil. Pertronix will not run correctly through a ballast resistor or the factory resistance wire in a points car. Glad you have it figured out.

Here's what I measured:

The alternator is putting out a very healthy 15.27v at the rear post.
The positive wire going into the coil reads a little over 14.2v.
Measuring across the coil's posts with the car on, but not running, reads 11.23v
With the car running at idle the coil reads 6.80v. It drops to 5v when I rev the car.

Since the voltage going into the coil isn't the same as going out, it seems like the coil might be the problem?

[West Coast GTO]

I recently rebuild my 455 and had the worst time getting it to idle and the timing to not jump from 12 to 15 to 18 and back to 12( a very long post here with many members opining on just what the problem was). I chased down every suggestion and, after removing the MSD dizzy, coil and 6AL control box and replacing with a Davis HEI, timing is now rock solid.
That worked for me, your results may vary.

[kyle_blake]

hey, i'm no expert but the video of your timing jumping around at idle, I honestly didn't see anything bad there. I noticed your RPM were 50-150 rpm lower than second video. It's my understanding that a healthy camshaft at idle can cause a bit of that movement you see. Obviously seasoned vet's here could say if I am wrong. I've learned that if you have "timing IDLE CREEP" that your springs in distributor are too weak and as such are swinging out at IDLE causing erratic timing. I've just never witnessed it. Your distributor was gone through and extremely unlikely that springs are weak.

I'm wondering if the taylor made was made with EMF shield core and the other set was not? I mean you would think you'd have to ask for special order spark plug wires that do not have that EMF protection? Maybe with EFI now you have to ?

I've ran 3 different distributors, hei, points etc and my idle timing has always been a bit jumpy.

A way to look at it is, your total timing is lets say 36 at 3000 rpm , and you know your distributor mechanical is 18 degrees. 36-18 mechanical is = 18 initial. the guy who sold you distributor may of included that info.

so as you rev engine up slowly from 830 rpm watch timing and it should jump up around 1000 rpm or so...that is when mechanical starts.

hope this all helps.

[Cliff R]

Rollmaster timing sets do that, but typically most of the "bounce" is at high RPM when you follow them on the dyno with a timing light.

It doesn't seem to effect power but a product of the design. Unlike the factory timing sets there is not constant tooth contact and while the chain is being pulled deep into the gears.

I use the stock 3/4" wide Morse timing sets here and they run much smoother when you watch them with a timing light.....FWIW......

[Kenth]

Originally Posted by Verdoro 68

Here's what I measured:

The alternator is putting out a very healthy 15.27v at the rear post.
The positive wire going into the coil reads a little over 14.2v.
Measuring across the coil's posts with the car on, but not running, reads 11.23v
With the car running at idle the coil reads 6.80v. It drops to 5v when I rev the car.

Since the voltage going into the coil isn't the same as going out, it seems like the coil might be the problem?

Sounds like you´re using the points ignition resitor cable to power the coil for the Pertronix?
I would use a single 30 A relay. Remove wire(s) from + on coil and use this to control the relay at post 86 on relay, post 85 to chassis ground, 30 to battery and 87 to + on coil.

HTH

["QUICK-SILVER"]

Which Ignitor and what coil are you using?

Ignitors need battery volts.

Coil volts depends on the coil being used. That's wheather or not it needs a resistance wire.

Ignitor III is multi spark and can show up on a timing light as two flashes. First flash being initial timing and the second being the ratarded extra spark.

Timing light picking up two sparks is what messes with the tach reading.

Clay

[mgarblik]

Originally Posted by Cliff R

Rollmaster timing sets do that, but typically most of the "bounce" is at high RPM when you follow them on the dyno with a timing light.

It doesn't seem to effect power but a product of the design. Unlike the factory timing sets there is not constant tooth contact and while the chain is being pulled deep into the gears.

I use the stock 3/4" wide Morse timing sets here and they run much smoother when you watch them with a timing light.....FWIW......

The flat link chains with the plastic cam sprocket is the smoothest of them all. May be some of the reason the OE's went that direction back in the day. Some Stock and Super Stock NHRA guys seek out these sets with the plastic sprocket for the rock steady timing. Obviously, we all know the durability issues on poorly maintained engines. But with modern oils, and the low miles most hobby engines see, that might be an option. Personally, I have had no issues with Cloyes top shelf double roller offerings. Their chains are far superior to the Rollmaster sets, even though they use the same chain manufacturer. They are made to different specs. JWIS chains from Cloyes are the superior chains. Rolon, (made in India), is used by Comp, Edelbrock and many others. Lower quality chains.

[BILL BOWMAN1]

I fought this issue many years ago. I believe it was from the MSD. I switched to a self battery powered timing light and it solved it.

[Cliff R]

"The flat link chains with the plastic cam sprocket is the smoothest of them all. May be some of the reason the OE's went that direction back in the day. Some Stock and Super Stock NHRA guys seek out these sets with the plastic sprocket for the rock steady timing. Obviously, we all know the durability issues on poorly maintained engines"

Correct, nothing out there faster than a 3/4" wide factory timing set with a nylon top gear. They'll run forever in a race engine but as wel know after 100,000 miles and not enough oil changes plus a couple of overheating sessions they start to flake off some teeth! I've never been comforable using them when they were available but love the factory type sets with the heat treated metal gears and would use the variety with the cast iron sprockets WAY before I'd put any type of "double roller" into one of these engines......FWIW....

[Verdoro 68]

The Taylor wires aren't anything special. Just off the shelf cut to fit 8MM Spiro Pros.

Originally Posted by "QUICK-SILVER"

Which Ignitor and what coil are you using?

Ignitors need battery volts.

Coil volts depends on the coil being used. That's wheather or not it needs a resistance wire.

Ignitor III is multi spark and can show up on a timing light as two flashes. First flash being initial timing and the second being the ratarded extra spark.

Timing light picking up two sparks is what messes with the tach reading.

Clay

I've tried an older Ignitor I and a new Ignitor II in the distributor. The coil is an Ignitor II. I don't believe those are multi-spark units. I've been running a Pertronix for years and haven't seen this issue before.

Originally Posted by Kenth

Sounds like you´re using the points ignition resitor cable to power the coil for the Pertronix?

The wire going into the positive post on the coil from the wiring harness is 14.2v. The Pertronix positive lead is run off the positive coil post so it should be getting the power it needs.

I'm pretty confident it's not the timing chain since a plug wire swap fixed the issue - or at least band aided it. Also, the RPMs were toggling intermittently at the timing light which wouldn't be a timing chain thing.

This is pretty much the same ignition setup I've been running for years, it's just all new parts, so I'm not sure what the culprit is. Maybe something changed in the way the parts are manufactured that's causing the issue.

[HWYSTR455]

Put an ohm meter on the 'bad' wire, and move the wire around. Bet you will see the conductor or cover is broken and is causing the issue.

Bad wire or arcing it what this sounds like to me.

The MSD super conductor 8.8 wires are my go-to, and I make my own lengths. It's hard to find a good wire these days.


.