Need advice from experienced Windsor builder
 

Just replaced my harmonic damper because the old one had gotten antifreeze dripped on it during life with the P.O., and was impossible to read the markings.
I decided to check to see that TDC on the damper (zero degrees) lined up correctly with the timing tab when the number one piston was at TDC.
Put a piston stop in #1, and ran it around both directions. Yes, checked to make sure I was on compression stroke, just because.
I found that when I hit the stop when going in normal crank rotation direction, it stopped at 4 degrees before the zero degree mark. (4 degrees BTDC)
Spun it the other way, and it stopped at 12 degrees before the zero mark. (12 degrees ATDC)
16 degrees total difference between the two marks.
To me, this tells me that I would turn the crank in its normal rotation direction for 8 more degrees, and I'd be at true TDC. (I know there's some slop, but I'm not going to pull the head to check it the "right way."

If I do that, the timing tab is going to be sitting at a point 4 degrees on the ATDC side of zero.

Here's where I'm confusing myself:
In a perfect world, I'd move the timing tab so that after I rotated that extra 8 degrees, it lined up on the zero mark.
I think that means I'd move the tab 4 degrees clockwise, viewed from the front of the motor.
Can anyone confirm that I'm on the right track? (or not)

But...even if I am right, the timing tab can't be adjusted. It's bolted firmly to the block with no provision to change its location.

So...how do I deal with that?

Do I just do the mental math when I put a timing light on it and make an allowance for the "missing" 4 degrees?

Sorry for the length of this, but it's driving me buggy and I hope someone out there can clear this up for me.

The way you found TDC is correct. I would mark the balancer with the correct 0 or maybe use the stick on timing tape from Summit Racing to mark it.

John

I'm not a big fan of the tape, as it's a temporary solution. You'll have to go through this process every time you adjust timing.

Use a quality paint pen, and mark 0*, 10* and 15*.

Or, you can buy and adjustable timing pointers from summit racing.

https://www.summitracing.com/search/...-block-windsor

I'm not a big fan of the tape, as it's a temporary solution. You'll have to go through this process every time you adjust timing.

Use a quality paint pen, and mark 0*, 10* and 15*.

Or, you can buy and adjustable timing pointers from summit racing.

https://www.summitracing.com/search/...-block-windsor

Apparently, I have a stutter. So I got that going for me. ;)

Another thing to consider on timing:
Comp cams and others grind their cams 4 or 5* advanced so when decreeing in a cam it might make a difference if you want to run the cam straight up and adjust it at TDC.
Perry:MECOOL:

HPD, I understand about cams being ground as you describe, but all I did was pull a balancer off and put a new one on. I would have thought that if the timing mark lined up with zero on the old balancer, it would be the same on the new one. I'm not sure how the cam grind would affect that, but if I'm missing something, please give me a bit more explanation.

Here is the important piece of the puzzle. The new balancer is clearly wrong.
The original combo showed all the possibilities of any error did not exist.

And we all know that this not related to cam timing.

But just for your info, your first pass at kissing the piston stop is at 4 BTDC on the compression stroke.
Now when turn the engine backwards to strike the stop again, you are chasing the inlet valve opening point, and around 10 ATDC is the closest point for piston to valve clearance, coincidence?
I would find another stop that kisses earlier in the stroke, and repeat your tests. For example, if you get 46 BTDC ad 54 ATDC instead of 50 in both directions, then your balancer is still incorrect.

Gaz64,
Did as suggested.
Got 16*BTDC, 24*ATDC
Still places pointer, when crank is turned 20* past the piston stop point, at 4*ATDC.
I've ordered an adjustable pointer that has 4* of adjustment, so I should be good to go.

Why is the degree scale on the balancer off?
Don't know, and I've concluded I don't care.
If the adjustable pointer lets me set the pointer to the zero mark when I know the piston is at TDC, I think I've got it covered.

Thanks to all for the suggestions and input.