Cam timing & wrist pin offset

[Thomas Tornblom <Thomas.Tornblom@Sun.COM>]

I degreed the cam last night, and I found that the cam was advanced by about 1 - 
2 degrees.

I have a new Crane hydraulic cam and a Manley true roller cam transmission.

I suspected that either the cam or the crank sprocket had a slight offset.

This morning, while driving to work, I remembered that the wrist pins on the TRW 
pistons have an offset from piston center. The effect of this is that the crank 
isn't at 0 degrees @ TDC of the piston.

1 degree offset @ 234mm (9.2") deck height equals 4.08mm in offset. I don't know 
what the wrist pin offset is, but it was easily visible, even though I didn't 
look specifically for it, so I guess it would be in that ballpark.

Is this the phenomenon I see? I can't remember which direction the pin offset 
is.

Has others seen this?

The cam transmission can be advanced or retarded by 4 degrees, and the only 
offset keys I've found has been for other engines.

Should I bother?

Thomas

Thomas Tornblom          Tel: +46 8 631 2100   E-mail: Thomas.Tornblom@Sun.COM
Sun Microsystems AB      Fax: +46 8 631 1102