Yep, It's 6.25.  For any others who may want to do this, I just cut a piece of poster board about 1/2" wide and approximately 4.909" (1/4 of the circumference) long.  Start at the zero mark on the damper and use the poster board to mark 270, 180, and 90.  I used a dab of white rustoleum primer.  That stuff seems to hold up well on an engine.  I had previously marked the damper up to 40 degrees with the same primer.  It's still easy to read after 10k+ miles.  I marked mine to simplify valve adjustment checks.  The marks aren't dead on but they're very close, close enough to check valves.


Lawrenceville, GA

Thank you, guys.  I think it's a car damper.  The engine came out of a '59 Fairlane.  I'll work with the 6.25 diameter.  If that's not right I guess I'll have to stop being lazy and measure it.


Lawrenceville, GA

Charlie,

         Based on the 6 1/4 inch diameter the circumference would be pi times 6.25 or 19.64 inches. Divide that by 36 = .545" for ten degrees. Even if the diameter is different, use that number and the same formula. 

Frank/Rebop

Bristol, In ( by Elkhart) 

Charlie:

The passenger car damper measures 6.250 diameter.  I don't know if your truck has a different size damper or not.  At any rate, your damper should have some degree marks on it, maybe a total of 10 degrees, some have more.  Anyway, you can use a pair of dividers, or even a grade schooler's compass, set it to match the degree marks on your damper and step off your desired marks.

John in Selma, IN

John - "The Hoosier Hurricane"

Anyone know the diameter of the mass behind the pulley? I want to mark 90, 180, and 270 degrees. It looks like the lower left in the picture in this thread: http://www.y-blocksforever.com/forums/Topic9246-3-1.aspx?Highlight=damper


Lawrenceville, GA