View single post by Mark Rosenbaum
 Posted: 11-21-2006 04:31 am
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Mark Rosenbaum



Joined: 03-12-2005
Location: Kingman, Arizona USA
Posts: 532
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 Cam timing is discussed in section A52 of the shop manual as well as other locations in the factory documentation.  What they tried to say is:
  • 100 IN / 110 EX - North American engines only, #10480 up only (meaning T-prefix air pump engines).  JHs and GTs with this cam timing typically run poorly compared to earlier cars.
  • 110 IN / 110 EX - Engines #4040 to #10479, and #10480 up for other than North America.
  • 115 IN / 115 EX - Engines #4039 and below.
Your engine #7306 should be set to 110 IN / 110 EX.  Since your photo shows 115 IN and unknown EX, the cam timing is not correct.  It will run that way but performance may suffer.  You can get the correct timing without spending money on parts as the gears are reversible.  WARNING: considerable care must be used to avoid bending your valves.  This was a hot topic for a while on the old JHPS site, so a search there should be beneficial.  I think there's a decent cam timing procedure in there somewhere, too, but it's been years and I could be wrong.

I've attached an annotated photo of two identical cam gears with their different faces showing.  This should clarify how most gears are marked.  Some folks have trouble picturing how things should be arranged, however, so for them I suggest printing out the photo, cutting out the two gears and arranging their pictures for the proper timing, then making the car look like the arrangement.  Paper dolls, yes, but it works.

As for your crank pulley and its timing marks, possibly a PO added additional marks for some unknown reason.  I would try to determine whch of the marks actually was TDC before doing anything else, specifically including altering the cam timing.  This can be a bit tricky to determine, as the #1 piston moves only 0.026" from 10°BTDC to TDC, but with repeated attempts it should be possible to make an accurate determination.  Then just put a daub of paint on the correct notch in the pulley. 

If you have trouble with any of the above, contact me directly and I'll see what I can do to provide a bit of guidance.  Good luck

Attachment: cam gears annotated.jpg (Downloaded 78 times)