Distributor / Timing issues

[alstaz]

What would cause my timing not to "hold"? Each time I get into the truck and start it, it runs a bit differently. I check the timing and it has changed. The hold down clamp is tight so the distributor isn't moving.

So far, while working on tuning my 69 Fj40 and I have replaced the points, (gapping them to .018") cap, rotor, wires and plugs. I have a Holley carb on the rig and have set the idle, float level and mixture. I get it running just "right" and then when I come back to the truck later the timing has changed. Do I have gremlins playing a trick on me or what?

Can the distributor itself go bad?

Any help would be great.

 

[Coolerman]

Check the top end of the dizzy shaft for side to side play. Remove the rotor button, turn the dizzy so that the points are open, now grab the shaft and try to wiggle it side to side. If you have side to side play you can actually see the point gap opening and closing. If it's bad enough it will affect the dwell.

 

[Coolerman]

Oh and don't forget sticking advance weights, broken springs, or sticking breaker plate. Are you running a OEM 1969 dizzy or have you replaced it with a vacuum advance model? Delco -Remy?

 

[alstaz]

Hmm good question. I am assuming that it is a stock distributor, but it does have a vac advance on it. The points I put in it are for the stock one as well as the cap and rotor.

The cruiser is a 9/69 model so it could have some 70 stuff on it.

I did notice that the hold down on the dist is a kind of a small handle. You turn it (without tools) to loosen it and tighten it. As I am setting the timing, when I tighten the dist the timing changes a bit, so I usually have to rotate it so it is more advanced and as I tighten it down it backs off a bit to my timing mark. is this normal?

 

[CruisinMT]

I did notice that the hold down on the dist is a kind of a small handle. You turn it (without tools) to loosen it and tighten it. As I am setting the timing, when I tighten the dist the timing changes a bit, so I usually have to rotate it so it is more advanced and as I tighten it down it backs off a bit to my timing mark. is this normal?

Thats exactly what mine does as well. I think it's fairly common.

 

[JohnnyC]

I have one of those handle dizzy claps also....i dont recall mine changing when i clamp it down...but...i do keep it a bit on the snug side when i adjust and use a screwdriver thru the handle to clamp it down tight....

are you noticing that its coming loose?...try to tighten with a screwdriver?

 

[CruisinMT]

make sure you are tightening it down enough. worst case scenario which actually happened to me. My timing gear on my cam slipped and took out the c-clip and put it through both my timing gears up front. but my rig ran like total s*** and it took me a while to figure it out while dinking around with it in my shop. make sure you are clamping it down tigh enough then make sure your dizzy is working properly etc. make a checklist of what you think it may be and go through each item making sure everything is in spec.

 

[alstaz]

I have one of those handle dizzy claps also....i dont recall mine changing when i clamp it down...but...i do keep it a bit on the snug side when i adjust and use a screwdriver thru the handle to clamp it down tight....

are you noticing that its coming loose?...try to tighten with a screwdriver?

No it really doesn't seem like it is lose at all after I crank it down. I give it a quick check and see if I can turn it before I loosen it back up.

I have a feeling that the dist shaft is loose enough to throw things out of wack. Maybe I'll try one of the non usa distributors I have on my other rigs and see it it continues.

 

[Pin_Head]

Worn distributor bushings tend to make the timing jump around a bit when idling, but it won't change the average timing. If the centrifugal weights stick, this might make the timing look different depending on where they stick and when.

 

[fireflyr]

I was having the same problem when I got my engine back in. I had also rebuilt the carb (Weber) and put a DUI distributor in. In the process of rejetting the carb I read that if you have the idle screw too far in it changes the vacuum dynamics and can mess up the timing. Is your vacuum coming off the base of the carb or the intake manifold? If you have exhausted all of the electronics variables, you may want to look at carb set up and vacuum. Just my .02. This was in the Weber info:

DO NOT hookup the distributor vacuum advance to the intake Manifold. That does not work and is a common mistake we see. If you do that you will pull full advance at idle then as soon as you open the throttle it loose vacuum and the timing will retard quickly causing a big stumble or flat spot and very bad throttle response. [FONT=Arial, Helvetica, sans-serif]
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[ducktapeguy]

How much does the timing move, and does it always move in the same direction (advance or retard)?Could it be that your distributor gear is loose on the shaft?

 

[fj404life]

My 69 dizzy was all gummed up. After cleaning and a light grease on moving bits its purrrrring. I had the same symptoms as you as well as a hard hot start as the timing was so advanced by the PO trying to make it run right. They are pretty simple to tear apart. My shaft was a lil sloppy also but seems to work fine after cleaning up the weights etc.

 

[vk7ybi]

Burning points will cause an advance in timing.. As the points burn away, the gap increases, when the gap increases the open duration increases, as the open duration increases the points must open earlier and close later, if the points open earlier, the timing has advanced. This symptom shouldnt be noticable from one start the next, however..

 

[alstaz]

Well I found the problem

After checking the distributor shaft for play I found that there was significant wobble. I pulled it out and swapped in a non USA dist to compare and after resetting the points gap it and clocking it correctly it fired right up.

It now runs soooooo much smoother and holds the timing I set. I found that the change in timing that was occurring, when I would tighten the dist down, is all but gone. I suppose that with that much play in the shaft, it makes sense that it was unpredictable.

It was a stock toyota distributor that was on there with a vac advance. I may clean it up and keep it as a trail spare. I wonder if I can fix the wobble issue...hmmm.

For now I'll drive it for a while and see if all is good. Thanks everyone for your suggestions and help.

 

[ken_79-fj40]

Good to hear you got it resolved. I had a similar problem on mine which has a mallory full mechanical advace dizzy with a pertronix installed. My truck would sometimes be very difficult to start, sometimes it would run great, other times it would ping like crazy, and every time I checked the timing it seemed to be off a bit. Well when I was tearing my 2F down for a rebuild last fall I discovered the roll pin that holds the gear on the distributor had broken at some point, and only a tiny piece of it was rattling around in the hole. So the gear could move quite a bit in either direction, but the shaft was always still turning.