[DeTomaso] Rocker geometry problem solved

[doug351c]

Jack,

To make the larger pushrod relief, I clamped the rocker's axle in a
machinst's vise, clamped the vise to the Bridgeport's table and then used
the rocker's own pivot axis to control the cut.  I did this by bringing the
7/16" dia milling bit in so it was making a cut and then rolling the rocker
body by hand against the fixed position rotating bit.  The end result is
that the relief follows the curvature of the rocker body.  A side view
picture of the rocker would show this but, sorry, I don't have a pic.
Scorpion just suggested using a die-grinder by hand, which would certainly
work, but I had access to the mill so why not use it?

Doug
  -----Original Message-----
  From: JDeRyke at aol.com [mailto:JDeRyke at aol.com]
  Sent: Thursday, December 30, 2010 11:16 AM
  To: doug351c at gmail.com; detomaso at realbig.com
  Subject: Re: [DeTomaso] Rocker geometry problem solved


  Good diagnostic job, Doug, and some neat machining! To all- because the
direction of the pushrod relative to the rocker changes during the valve
cycle, more clearance should be cut at the bottom of the rocker than at the
top. Now, paint the clearance slot you cut with Dykem-blue or some brittle
lacquer and run the engine hard, then check a couple of rockers to see if
you cut enough clearance everywhere. Rub-marks will show where you need a
little more hand-contouring. This will be a worse problem on most aluminum
roller rockers if you run 3/8" or larger pushrods- which are recommended for
high rpm use. The cut area on most rockers is only significant if you run
locomotive-strength valve springs and/or over 7000 rpms. Then, stronger
cast-stainless-steel roller rockers are indicated.

  A second thing that sometimes bites guys is, the roller rocker's pivot
shaft must be dropped onto the rocker stud with the round side down. This
puts the machined flat spot on the pivot shaft upward where the rocker nut
can bear solidly against it. Roller rockers can be adjusted to work either
way but the lock nut won't have enough surface to bear against if the round
side is up, and your valve clearances will constantly change- sometimes in
only 50 miles! Cheers- J Deryke