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841 timing marks only visible when #4 fires - huh?

W

William Fissell

Member
Hi, All,

trying to time my 841. The dizzy seems a little
messed up, as there was brass dust all over the
inside of the cap, it has the wrong rotor, lacks
the distributor shaft clip.

Anyway, the thing runs but I was confused that the
timing marks only show up when the #4 plug fires.
I thought the flywheels were indexed to the crank
in such a way as this could not happen.

I'll get a new cap and rotor and clip; the rotor
is slapping around so much that the timing is
quite jittery now. Any reason to try to think
about remedying this, or just go ahead and time
off #4 and move along?

thanks!
 
The pistons in cylinders 1 and 4 are both at TDC at the same time. If #1 is on compression stroke #4 is on exhaust stroke and vice versa.
I assume you are shining a timing light though the "window" in the block onto the flywheel? And the flywheel marks are illuminated by the light only when the light is connected to the #4 plug wire? When you connect the light to #1 plug wire the light does not flash? If this is all true then you are not getting any "fire" through the #1 wire to trigger the light and your engine is running on 3 cylinders.
Regardless of what's happening you can indeed set the initial timing using the #4 cylinder and verify that the advance mechanism inside the distributor is working by revving up the engine and confirming that the timing does advance.
 
Number 1 and 4 are companion cylinders both will fire at the same tdc mark only 360 deg apart. Do you not get a light on number 1?
 
1. 1 & 4 fire a turn apart at the same point/timing mark on the flywheel, and 2 & 3 fire 180º from there, halfway around the flywheel. (1 & 4 crank throws are on the same plane, as are the throws for 2 & 3.)

2. Spark occurs when the breaker points OPEN and the statement "the rotor is slapping around so much that the timing isquite jittery now" is NOT valid. However, wear/looseness/slop in the distributor gears/shaft/advance mechanism CAN casue the timing mark to move around.
 
Hi, all,

Yep I get the light flashing on all spark plug wires, but when I peek through the hole at the timing marks, I only see them when the timing light is clipped to number 4, not at all when clipped to number one. Wires 1and 4 are diagonally opposite each other on the distributor cap and I verified tdc by feeling through the spark plug hole when the rotor was pointing at the #1 wire.

I see your point about points and it was maybe a dumb idea to blame the jitter on the rotor. But holy cats it"s jumping around.

Thanks for your help.

Bill
 

Distributor shaft bushings do wear out you should not be able to wiggle the top of the shaft it should be just loose enough to spin easily.
 
(quoted from post at 18:08:13 04/03/14) Once you get the correct rotor with the clip the jitter will probably be less.
Click to expand...
Probably" not, as Bob has already stated, " Spark occurs when the breaker points OPEN and the statement "the rotor is slapping around so much that the timing isquite jittery now" is NOT valid"
 

Isn't it the clip that keeps that rotor from twisting around?

I know in a fix you can use plumbers tape in place of the clip. That will get you enough time to finish the day and get a new part, but it won't last for too long. I figured something like that might be happening with William.
 
What I am most peeved about is that I ordered a
handful of clips last time I needed one.. and they
are all safely hidden away somewheres.
 
That would be me for sure. I'd find them as soon as I went to put the new ones away.

I've got a pie chart hanging in my shop about how I spend my time.
5% Cleaning
5% Designing
5% Creating
5% Finishing
80% Looking for the tool I just had in my hands

It's more true than I care to admit.
 
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