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Weird timing issue.

I think this is weird, or maybe its normal. I don't know.
Anyways, when I go to check my timing my numbers seem weird to me.
I have 14 degrees of advance built into my distributor. When I set the digital timing light at 0 and point it at the pulley. The notch is way to the left of the fan housing mark, ATDC. It is a clockwise rotating distributor.

If I set about 14/16 degrees of advance into the timing light, it brings the notch up to center. But it brings it up from ATDC. Is that right?

Now if I set 26 degrees of advance into the timing light, the notch is on the right side of the pulley, BTDC. Then when I rev it the notch moves to the left and settles on the center line.
Is this normal?

I would think that the 14 degrees built in would be on the BTDC side. It is very puzzling.
So basically when I set timing at 26 degrees BTDC it settles down to 14 ATDC.
Im confused.

I keep thinking that with the light zeroed out i should see the timing somewhere around 12 BTDC not ATDC. That way my 14 built in advance and my 12 initial would add up to 26.
my head hurts.

What do you guys think?
thanks.

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Old 05-18-2012, 08:48 PM
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hi,
Depending on the timing light your using, if you preset the timing degree's into the light then you should see the TDC marks lining up, if they dont then you move the disi to correct it, i am sure this is correct for most lights but hopefully others will coment further when we know the light your using etc.
Anthony.
Old 05-19-2012, 02:16 AM
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I am pretty sure my timing light is ok. I do have a MSD light too and I will check with that also, but it doesn't have an advance dial on it.
But it is harder to use because I have a serpentine belt system and a pulley with no 26 degree notch on it. The only notch is TDC.

I just keep thinking I should see 14 degrees of advance, not retard. When I check initial.
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Old 05-19-2012, 07:32 AM
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If the marks line up at 14 btdc, then that is what your timing advance setting is.
Old 05-19-2012, 10:48 AM
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Quote:
Originally Posted by rusnak View Post
If the marks line up at 14 btdc, then that is what your timing advance setting is.
Maybe I am explaining this wrong. I have 14 degrees of total advance in my distributor, I didn't make that clear earlier when I said built in, I meant total. That was my mistake, sorry.

So if I have 14 degrees of total advance in my distributor. Why is my initial spot ATDC and not about 12 BTDC when I set my dynamic at BTDC 26?

Could my distributor be off a tooth? Or maybe my pulley wasn't installed at exactly TDC?
I have checked the timing on both upper and lower #1. It is the same with both.

It runs O.K. I'm just wondering if something is not right.
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Old 05-19-2012, 12:49 PM
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Do you have a remote starter button? If you don't trust the pulley, then check tdc by sticking a piece of rubber hose into the sparkplug hole for cyl#1. Crank the starter until a puff of air comes out. I use a safety ear plug jammed into the hose. You could be either looking at the wrong mark, or have the timing light set to the wrong # of cylinders, etc. This will baseline the mark for you
Old 05-19-2012, 01:27 PM
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Timing light set to wrong # of cylinders? Never knew you could do that.
If the light just reads a pulse off the wire, why does it care how many other wires there are? That's interesting.
There is a little 4 in a circle of arrows on my light, but it is not changeable.

Maybe I'll pull that plug and stick a straw in there or a hose and see if I really am at TDC.
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Old 05-19-2012, 01:37 PM
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I'm pretty sure the '4' on your light is just for indicating a 4-stroke engine. 2-cycle or rotary
would be very different.

Also, if you have 14 degrees advance on your distributor, but the distributor turns at
half the crank speed, that means you would see 28 degrees total on the crank. You said
your total measurement is 26BTDC when initially (idle?) at 0ATDC. 26-28= -2 (+2ATDC)
which is close to 0.
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Old 05-19-2012, 03:06 PM
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Gotcha. But I am not at 0ATDC at idle. I am at 14/16 ATDC. It is really strange.

I am setting timing at 26 BTDC at 4000 rpm and i would think that with only 14 degrees of advance in the distributor. My initial would settle about 12 BTDC.
It is not. It is ATDC.

I can not seem to figure out what would cause this.
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Old 05-19-2012, 04:06 PM
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So I guess I don't understand what your term 'initial' means.

Again though, you cannot use 14 degrees advance in the distributor
in the calculations for what is happening at the crankshaft. You must
use 28 because the distributor shaft is at half the speed. So if you are
at 26BTDC and at full advance, then taking all the advance away
leaves 2ATDC.

For a sample, look at the chart below which is for early E,S cars.
These are timed at 30BTDC at 6000 RPM. Note the numbers for the
distributor shaft are half and its RPM is half.
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Old 05-19-2012, 06:24 PM
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You have a few missunderstandings. When you set the timing light to zero, the TDC notch on the pulley is to the left of the center mark on the alternator housing. This is BTDC not ATDC. The pulley turns clockwise. When you set 14 degrees on your timing light it delays the flash by 14 degrees so you see the mark when it reaches TDC. I would be helpful to you to leave the light at zero and run the engine up and down to see what is actually happening. You should see the timing at 14 BTDC (TDC mark to the left), as you rev the engine you should see both marks move furthur to the left and if you have a 26 degree mark it should center up on the alternator housing at high RPM.

-Andy
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Old 05-20-2012, 06:17 AM
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Humm, So maybe I'm not crazy and this is normal. I'm going to look at it again today, with what you guys said in mind.
I wish I had better access to the pulley, I would love to put a 26 degree mark on it and ditch the digital timing light.
Any suggestions. Here is a picture of it. As you can see measuring diameter/ circumference or ? would be challenging.
There is no way to remove or get access to the pulley without dropping the engine and that is not going to happen today.



This one is just gratuitous.
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Old 05-20-2012, 08:26 AM
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Two ideas. What engine do you have. Does it have a vacuum line at the distributor? If it does, that should be disconnected before checking the timing. Also when I put my MSD in the multipole discharge at low RPMs caused my timing light to go bonkers. MSD recommends their light because of this. I got the MSD light that corrects for the multiple discharge and all is good. Hope this helps.
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Old 05-20-2012, 09:01 AM
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Thanks guys, I think everything is cleared up now. It all makes sense now.
What I did was take a very skinny tape measure and measure the diameter of the pulley. I think it was 4.75. Then I multiplied that by Pi to get the circumference. Then I divided the circumference by 360 and multiplied that by 26.
I ended up with 1 1/8" for 26 degrees.
Then cut a thin piece of masking tape 1 1/8" and stuck the edge on the notch and checked the timing at the leading edge.
26! approximately.

I guess nothing was wrong after all, but thanks for walking me through everything. I can be such an idiot sometimes.
Thanks again.

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Old 05-20-2012, 12:42 PM
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