304 timing mystery

my plug wires have always seemed to be 180 degrees off so I went to verify TDC on the compression stroke for cylinder 1 and found that the rotor was pointing at the opposite side. so I moved the plug wires around so that everything lined up and the wires were right and of course, it wouldn't run. I put everything back the way it started and it runs fine. What's going on?

 

The last time some one replaced the distributor they aligned the marks on the harmonic balancer to TDC but didn't make sure that it was on the compression stroke, they had a 50-50 chance.
Your motor doesn't care about the orientation, it will run the same.

If it really bothers you, that's a differant topic.

 

That's correct - the orientation of the distributor in the engine is arbitrary. All that is required is that the rotor points to the #1 wire at #1 TDC, and the wires are in the proper order after that.

If it bothers you, remove the distributor, turn the rotor 180 degrees, and put the wires back in the "correct" locations.

 

Here's the mysterious part with pictures to better illustrate my question. With Cylinder 1 at 10 degrees BTDC on the compression stroke (determined by spark plug loose and I hear 'pssssss" as I turn by hand ) I would expect to see the rotor pointing at the #1 plug wire terminal. instead I see this -

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That's the timing mark, not the rotor. Looks fine to me.

EDIT - ok, that's the rotor. So you are worried that it's somewhere other than the location in the book? We understand what you are referring to, and the answer does not change. As mentioned above, it's arbitrary. Does not affect performance. If it bothers you, remove the distributor and rotate it 180 degrees and rearrange the plug wires. Or don't... not a problem. I would leave it alone.

 

The terminal with the boot off is the one that the cylinder 1 wire is normally attached to so how is it firing with the rotor pointing the opposite direction?

 

The plug wire going to #1 cylinder is located in the cap, above the end of the rotor.
You seem to be more concerned about the fact that your distributor wiring isn't the same as a picture in a book.
The last time the dist. was installed, it was turned 180 deg from where it was placed at the factory.
All of the wires were rotated 180 deg so they are in the correct place relative to the rotor.
It will run fine the way it is as long as you have enough space to set the timing.
If it bothers you that much, you change it like Tim said so the rotor is set back to where it was from the factory, then rotate the wires back to match your picture.

I just re read my post, sorry, it's a bit um, rude.
I can't think of a way to describe to you why the distributor still works the way it is.
Nor should you just believe what we say without figureing it out yourself.
If you can find a mechanic who will let you watch over his shoulder while he changes it back to origional, he may be able to explain it better.

 

Thanks for your patience guys. I agree with and follow what is being said and I'm not concerned about where the number 1 plug wire is on the cap relative to a picture in the haynes manual! Sometimes I do get up in the middle of the night and go down to the garage just to make sure all the valve stems are clocked the same but I'll save that for another post Anyway, obviously I'm not thinking this through - I'll look at it again tomorrow. Thanks again

 

Dave,

As I see it, the cap without the wire at the ~10 oclock position in the picture is #1 cylinder. The next pic without cap shows the rotor at ~5 oclock and is in the position you believe to be at BTDC 10* on #1 and so *should* be pointing to #1.

I would suggest that, because your Jeep does run, that when you turned the engine by hand and thought you were at BTDC 10* on #1, you are actually on the exhaust stroke and therefore 180* off from where you thought.

 

That's what it was Norm - which of course is what it had to be. What presented itself an elusive timing mystery i.e. "how can it run when it 180 degrees out?", was in fact a perception trick. While laying underneath the jeep and turning the engine by hand from below, I could plainly hear air escaping through the partially unscrewed spark plug in cylinder 1 that would indicate the compression stroke. In fact, what I must have been hearing was air on the exhaust stroke being forced through the exhaust manifold which was closer to my ear from down there. (I couldn't hear the compression stroke plainly until I tried the next morning when it was nice and quiet in the garage and then it dawned on me what was happening. )

Anyway, all is well. My apologies to the forum for the drama but hopefully someone will at least get a good laugh!

 

The whoosh method works ... if you crank it with the starter motor. Take the distributor cap off, #1 spark plug out, and watch the rotor as you crank the engine. You will get a loud whoosh on the compression stroke as the rotor passes the post for the #1 wire.

 

I know from experience...I did the same thing while trying to set timing for mine the first time around...it's an easy thing to do.