Date:         Wed, 26 Jun 1996 10:12:00 -0700 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         "Maher, Steve (SD-MS)" <SMAHER@gi.com>
Subject:      RE: Request for .009 timing measurments


>Does someone have the measurements [inches or cm] from 0
>on a stock-sized crank pulley for 7.5 and 30 BTDC? I seem
>to remember 7.5" being about 3/8" to the left of 0.


Yes, that's *about* right.  <--- (big help, huh?)

But consider that the pulley has 360 degrees.

Measure its diameter, from the point where one of the timing marks is,
across to the opposite side where a timing mark would be if it had one
there.

* Multiply this diameter by 3.1416, to get the circumference (the distance
  all the way around the pulley at the rim).

* Divide the circumference by 360 to get the spacing for one degree.

* Or, divide it by 48 to get the spacing for 7.5 degrees-- this is the
  distance from the 0-degree mark to the 7.5-degree mark.

* Or, divide it by 12 to get the spacing for 30 degrees-- this is the
  distance from the 0-degree mark, to where you have to put a chalk mark
  for 30 degrees.



I don't know the exact diameter for a VW pulley, but here's an example.

* If the pulley is, say, 9 inches across, then the circumference is
  9 x 3.1416, or 28.27 inches. If you wrap a cloth tape measure around
  the pulley, it should show this-- 28-1/4 inches, or just a hair more.

* Divide the circumference by 360:  28.27/360 = 0.079 inches, or about
  two and a half thirty-seconds of an inch-- about the thickness of a dime.
  This is the spacing for one degree.

* Divide the circumference by 48:  28.27/48 = 0.59 inches, or slightly
  more than half an inch. This is the spacing from the 0-degree mark to
  the 7.5 degree mark.

* Divide the circumference by 12:  28.27/12 = 2.36 inches, or a hair less
  than 2-3/8 inches. This is the distance from the 0-degree mark to where
  you have to put the chalk mark for 30 degrees.


Don't use these numbers quite yet-- first measure your pulley. Stick a
tape measure down into that little well that the bottom of the crank
pulley sits in, hook it on the bottom of the pulley, and hold it flat
as you can against the top edge of the pulley-- that's the diameter.
Multiply that distance by 3.1416 to get the circumference, and use that
number instead of 28.27 to get the three distances above.

Good luck!

Steve Maher   smaher@gi.com   75461.1717@compuserve.com