timming jumping around?

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SRT_DSTRHOLC

SRT_DSTRHOLC

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What would cause my timing to be jumping around? vac. leak?
 
74Burntorange said:
What would cause my timing to be jumping around? vac. leak?
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Timing chain loose, centrifugal advance sticking or springs missing, slop between the cam gear and dizzy drive gear, rotor loose on dizzy shaft, plate inside dizzy that vacuum advance pod operates is loose therefore moving reluctor around. I'm sure I missed something. BTW, the ignition timeing will move around normally 1 or 2 degrees cuzz of normal looseness, electronic crank referenced is dead nuts.

Terry
 
its a new motor and new chain so im thinking something with the dizzy and theres no vaccum on this dizzy
 
The first thing that comes to mind not mentioned above is excessive cam endplay. Weirdness in the distributor is more likely the culprit.
 
Ooh ooh let me try!! I just had this problem with my pretty fresh motor. I found out that the dizzy (dist.) cap was loose on the dizzy (dist. again) I screwed it down instead and it helped a lot. So there I am thinking I'm all good go for a ride that was cut short when my intermediate shaft bushing was sloppy and caused the gear to wear out. Beware of the shrapnel!!!!!!
 
I would pull the distributor and do a very thorough inspection,maybe a screw loosened out and could be bouncing around in there,doing more damage!:sign6:
 
i was messing with the rotor earlier before i set timming. I think i need to tighten them more, does it matter if the rotor moves left to right like 1/4 turn?
 
74Burntorange said:
i was messing with the rotor earlier before i set timming. I think i need to tighten them more, does it matter if the rotor moves left to right like 1/4 turn?
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When you turn the rotor 1/4 turn,does it have pressure?Does it spring back when released?If not your rotor is foobard!
 
74Burntorange said:
sloppy how?
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The oil pump/distributor drive shaft runs through and sits on a hat bushing that is pressed into the block. If that bushing is worn it will allow the distributor drive shaft gear too much room to move around and it will destroy the cam and drive gear....and who knows what else!
 
Are you using a MSD or similar control box? If you are, then the timing will jump some depending on which pulse your timing light picks up. The way to check it is to dial your timing light up to your total timing and then check your timing when the engine is revved up to the all in point or just a little above that rpm (maybe 3500 or so). If it is dead on then the timing light is picking up different pulses and all is fine.

Jack
 
If the engine doesn't idle properly the timming will jump around. Just one bad plug or plug wire and yes a vacuum leak can cause it.
 
74Burntorange said:
What would cause my timing to be jumping around? vac. leak?
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Does it have vacuum advance on the dist? What is that hooked up to? Does it jump around when you unplug the vacuum advance?

I had mine hooked to the wrong (manifold instead of metered) vaccum nipple on the carb, and it caused the same problem. A very simple fix, but took a while to figure it out.
 
Coyote Jack said:
Are you using a MSD or similar control box? If you are, then the timing will jump some depending on which pulse your timing light picks up. The way to check it is to dial your timing light up to your total timing and then check your timing when the engine is revved up to the all in point or just a little above that rpm (maybe 3500 or so). If it is dead on then the timing light is picking up different pulses and all is fine.

Jack
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Jack is right on about this. This phenomenon is due to the multiple spark under 3000 rpm and it's nothing to worry about. Even if you dial it up to your intial timing at idle it tends to go away.

Also, have you checked your reluctor to pick up gap?
 
mopar340dave said:
The oil pump/distributor drive shaft runs through and sits on a hat bushing that is pressed into the block. If that bushing is worn it will allow the distributor drive shaft gear too much room to move around and it will destroy the cam and drive gear....and who knows what else!
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I had the same problem on my 360 I rebuilt 3 yrs. ago and didn't replace this bushing Dave's referring too. Made it real hard to set the timing right on cause it jumped back and forth 2-3 degrees constantly. I had to take it back apart to replace a defective oil pump and replaced the bushing and now the timing is rock solid.
 
I'm not that familar with newer style distributors, but 25 years ago I know that worn bushings in the distributor would do this. I suppose they still have bushings in them, not quite sure. Just a thought.
 
im wondering if the shaft is worn, because I took the cap off and tightened the rotor as much as possible and it tunred off fine but when I did it again seems like when it warmed it did it again maybe running to lean? to rich? not sure
 
also when i turned the car off it was still running but wanted to die sort of, so i turned the key back on and then off and then it died. Maybe a big vaccum leak some were
 
Look under the cap.. the rotor goes clockwise... where are the burn marks on the cap's terminals from the spark jumping? They should be centered and not all the way accross. Post a clear pic if you can.
 
74Burntorange said:
also when i turned the car off it was still running but wanted to die sort of, so i turned the key back on and then off and then it died. Maybe a big vaccum leak some were
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If your running the MSD box,with old dizzy,maybe it,s time for someone to go over your dist. and set springs or re-build?When you turn the car off and it stays running(kinda)this is called run-on,your timing sounds off.Try setting again,maybe to far advanced?I have fresh motor with the MSD box and pro-billet MSD dist,with springs set.Or just get a new MSD dist.(expensive)But worth the piece of mind.My 2 cents.
 
Run on is simply idle set too high in most cases. Do you have a tach and a vacuum gauge ?
 
Do you have the stock balancer on it.I had a 340 once that did the same thing and found out the rubber is the balancer was shot causing poor timing.Put on a new balancer problem solved
 
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