Odd Timing Issue

[MikeStang 247]

Okay so here is an odd one that I would like some opinions on.

My best friend's 69 Mach died on him the other day at his house, he went through the basic diagnostic procedure and figured out it wasn't firing, so he tested his MSD box, swapped to a known good coil and still had no fire, so he brought his MSD Dist. to the house for me to swap out with mine.

Tossed his dizzy in my car and it fired right up...hummm must be another problem.

So he loads car up and brings it to the house.

 

Motor is a 408 with Alum heads Etc... Ignition consists of MSD 6AL, MSD Pro Billet Dizzy with correct gear for roller cam and no vac advance as well as an MSD Blaster 2 Coil.

I reinstalled his distributor last night and the car fired right up, set the timing to 14 degrees after warm up and all seemed perfectly fine...let it run about 15 min and shot timing again and all of a sudden it started moving clockwise until the scale was no longer visable...So I thought Okay maybe bad balancer but decided to be sure it wasn't my timing light, so went to my car and hooked up light and it was rock steady.

Hooked light back to his car and timing was dead on and un-moving, then a few minutes later the scale went away again WTF.... Killed the car, pulled #1 plug and rotated to TDC and the mark on balancer was dead on zero.... Also the balancer is only a few months old and shows no signs of slippage, rechecked it again with light and now its rock steady and holding at 14 degrees and I couldn't make it start screwing up again....

So lets hear the thoughts?

I am going to mark the balancer on the inner and outer hub and run it and see if there is any separation of the marks, and if not balancer is good.

I also didn't notice any slack in the timing chain as I had him rotate the engine backward while watching the rotor and it moved almost instantly so no sign of timing chain stretch... Could the box be going out or possibly the New Distributor ?

[1969_Mach1 333]

Did the engine RPM change as the timing moved on its own?  If the timing is actually moving I would expect a change in engine RPM.  Is there something on your friends car causing electrical interference with your timing light.  Something different in the ignition systems between the two cars, plug wires, etc.?  Are you using a digital timing light?  MSD cautions the use of digital timing lights with their ignition systems.  Many digital timing lights do not work correctly with multiple spark ignition systems.  I would try a non digital timing light before going any further.  I use an old school Snap-On non digital timing light with a simple dial to adjust the advance.

 

MSD has a very simple no spark test procedure on their website.  With that test and an ohm meter you can quickly isolate the problem to the either the magnetic pick up, ignition coil, or MSD ignigion box.

[ray1970 88]

Not shore why there was no spark to start with there are to many possibility's

As far as the timing thing it sounds like its cross firing.. Be it a plug wire or distributor phasing its hard to tell from here. 

[Mach1 Driver 560]

Is the pin holding the dizzy gear snapped?

[SWPruett 83]

Check the locating roll pin in the reluctor wheel.  I have had these disintegrate and allow the reluctor to spin freely on the shaft causing all manner or mayhem.  When you pull everything apart, it all looks just dandy.  Worth a look.

[MikeStang 247]

Thanks Guys.

Rechecked the timing with my light and it was dead nutz on. don't remember the maker of my timing light, but its just got an on and off button, nothing special and its a few yrs old and works fine on my car, which has ALL of the same components as my biddies car does.

His Dizzy and coil are new and his 6AL box is several years old.

They did check the 6AL box before he brought it to me and it was fine.

 

So last night we marked the balancer and took it for a ride and it ran like a top with no problems and balancer marks appear to be in same location as they were when I marked them.

Distributor gear pin was not sheared off and looks just fine as well...This thing is Odd.

So we will be driving it for 5 plus hours to Cruising the Coast next week but we will have a Spare MSD box, spare known good Parts distributor and spare Coil Just in case HaHa

[ray1970 88]

I dont see anything ODD about the timing after having done hundreds of timing sets.. Plug wire bleed over is very common

and can make it a pain....I have seen a MSD ing spark jump 6in.... on a damp day it can be almost impossible

You most likely and without knowing fixed the spark problem while removing and replacing ing. parts.   

 

This is most likely it but not the only possibility..  

[MikeStang 247]

Yeah we ran it last night for an hour or so and seemed to have no problems what so ever.

On a side note we also replaced the 6k pill in the 6AL with a 7k Pill and talk about make her run Wow..amazing what a little more RPM will do HaHa