Timing marks

[sraiken]

The more I read the more confused I get.
On my 1980 911SC the spec is 5 deg before top dead center, On the crankshaft pulley there is a mark Z1(TDC) and a 5 deg mark to the right side of Z1. Based on the rotation of the crankshaft the 5 deg mark is 5 deg after TDC. So I believe that I should adjust the timing for 5 deg an equal amount to the left of Z1. This conflicts with Waynes !01 book on page 72 which has the arrow pointing at the 5 deg and calling it 5 deg BTDC?
Thanks
Steve

[911mot]

Use the mark on the bottom of the fan housing as the reference point. As the crankshaft turns, the 5degree mark will pass the reference point before the Z1 does.
If using an adjustable timing light leave light at zero and line up the 5 deg notch with the housing notch (by turning dizzy) or set timing light to 5dgrees btdc and line up Z1 with notch in fan housing(again by turning dizzy).

[sraiken]

I know about the mark on the fan housing as a reference, but the Z1 mark passes it before the 5 deg mark. My timing light can be set for advance and retard so I quess I will just do it that way. Thanks for your reponse

[911mot]

On the crankshaft pulley there is a mark Z1(TDC) and a 5 deg mark to the right side of Z1

I'm confused, doesn't the crankshaft rotate clockwise?
Or is the 5 deg mark to the left of Z1

[jacko241]

The 5 degree mark is to the right of the Z mark. It is the reference point for 5 degrees BEFORE top dead center, which is what the Z mark is. The 5 degree mark is indicating 5 degrees of crankshaft rotation is still needed before reaching TDC. Ignition advance is just that, firing the spark just before the piston reaches the top.

[Wil Ferch]

Check this ! .....

I believe some SC's are timed ATDC...and some BTDC....both 5 degrees.

Wil

[sraiken]

OK guys, it seems like my confusion is well founded. My crankshaft rotates counterclockwise. I have done cam timing (and valve adjustment for that matter) and I know that Z1 is top dead center for cylinder one. DO Not burst my bubble on that one, please. The number 5 marks 5 degrees one way or the other. Mine is to the right of Z1. So maybe Wil is about some being timed ATDC and some being BTDC. 5 degrees on the pulley amounts to a distance (chord length) of 5 mm so it is easy to just mark 5 mm to the left of Z1 and reference mark 5 deg BTDC. I know mine wants to be timed 5 deg BTDC.
I also wanted to ask how one gets to be more than a junior member on this board. Have fun

[stlrj]

My crankshaft rotates counterclockwise

If that's so then your fan will be going counterclockwise too which sounds baaakwards to me.

Joe

[911mot]

Put it in 4th gear and watch the crank as you push it forward, just to be certain

[Jeff Higgins]

As far as I know every 911 crank rotates clockwise when viewed from behind the car. You don't get to be anything more than a junior member until your crank goes clockwise.

[blue82coupe]

sraiken. To become a senior member, I believe you have to have 100 posts. I'm fairly certain your engine rotates clockwise... as viewed from the rear of the car looking to the front.The distributor rotates counterclockwise. The 5deg timing mark is to the right on my 82 sc.pulley.Dan

[jacko241]

I have never seen ANY engine that rotates counterclockwise. I am not saying there aren't any, just that in my 30 yrs in the auto biz I haven't seen one.

[TerryH]

http://forums.rennlist.com/rennforums/showthread.php?t=128799

Here's a thread on how to set timing that I read yesterday.

[sraiken]

Yes, my crank rotates clockwise......not sure how I got that backwards, but I feel like an idiot. Maybe I need to lower the dosage of my medications. Sorry.

[sraiken]

I did read the thread you mentioned Terry, thanks. The 35 degree at full advance seems high since my book says 23-29 degrees for my 80 911SC but I notice that the spec of 35 for previous years.