Please identify 1977 Carrera 3.0 timing marks

[Bill Jennings]

Hi,

Can anyone identify what these 4 marks are please.

I cannot see any identifying letters or marks on the face of the pulley.

Thanks

Bill

[T77911S]

clean off the front of the pulley and see if you can see a Z1 or any numbers. i just pulled my motor and finally saw that my timing mark was 35 degrees.
it can help to line the roto up to the timing mark on the dist if you can see Z1.

[Bill Verburg]

Originally Posted by Bill Jennings

Hi,

Can anyone identify what these 4 marks are please.

I cannot see any identifying letters or marks on the face of the pulley.

Thanks

Bill

From left to to right in the pic
the left most 2 notches are
5° ATDC 0(AKA Z1)

the right most 2 notches are
35°BTDC 30° BTDC

edited to correct for mis-remembered crank rotation

[Bill Jennings]

I've already tried to have a good look with a mirror but i'll try some carb cleaner on it.

[Bill Jennings]

Bill,

Many thanks I was reading them the other way round and that didn't make sense.

Any idea why the C3 timing is ATDC and most other 3 litre 911's are BTDC?

Thanks again

Bill

[Gib Bosworth]

What's interesting is that the 74/75 US Carrera spec book shows those marks as (left to right like Bill says) 5 deg ATDC, Z1 for the left pair, and 30 deg, 35 deg. BTDC for the right pair. The spec book for the Carrera 3.0 does not show the pully wheel diagram, and only lists 5 deg. ATDC for idle timing, and no timing number at 4000-6000 rpm. Why would there be timing marks for 30/35 ATDC?

[Bill Verburg]

Originally Posted by Bill Jennings

Bill,

Many thanks I was reading them the other way round and that didn't make sense.

Any idea why the C3 timing is ATDC and most other 3 litre 911's are BTDC?

Thanks again

Bill

for '976-77 C3,
Idle timing w/ distributor vacuum connected is 5° ATDC

[T77911S]

i was wondering the same thing. wouldnt the 30-35 degree marks be "BTDC"

[Bill Verburg]

Originally Posted by Gib Bosworth

What's interesting is that the 74/75 US Carrera spec book shows those marks as (left to right like Bill says) 5 deg ATDC, Z1 for the left pair, and 30 deg, 35 deg. BTDC for the right pair. The spec book for the Carrera 3.0 does not show the pully wheel diagram, and only lists 5 deg. ATDC for idle timing, and no timing number at 4000-6000 rpm. Why would there be timing marks for 30/35 ATDC?

to check timing at max advance

earlier models were speced to either 30° or 35° BTDC @6000 rpm

I may have gotten the left/right thing mixed up as I don't really remember which way the crank pulley rotates

if it is rotating clockwise in the pic then the right 2 are 30° 35° BTDC

and the left 2 are 5° ATDC and TDC(Z1)

[Bill Verburg]

I used to put a bit of phosphorescent chalk on the 5° ATDC mark, it would fluoresce under a timing light making it easier to see.

It appears that there is chalk on the left most mark, probably for the same reason

which means that if the pulley is rotating clockwise the far left mark is the 5° ATDC

[Gib Bosworth]

The engine rotates clockwise. Thanks for clearing up your previous comment, Bill, you comments are always on the mark, so I just was puzzled about that earlier comment.

[Bill Verburg]

Originally Posted by Gib Bosworth

The engine rotates clockwise. Thanks for clearing up your previous comment, Bill, you comments are always on the mark, so I just was puzzled about that earlier comment.

It's been a looong time since I swapped that engine out