1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Saabu,
What is happening is called "stacking tolerances". The polishing job probably removed half a thousandth off the crank. Both VV and FM are a little on the "loose" side. All this stacks up to two-thou clearance. Remember, these clearances are for newly done motors only. They'll actually run fine with five-thou clearance in a mega mile situation.
Two-thou on the SAAB big end bearings is perfectly acceptable. If you want it smaller, you're looking at having your rods resized. The machinist cuts a small amount off the mating surface between the rod and cap. Then they recut the hole in the big end to the proper size.
The cost for that procedure is quite a bit. You can run your two-thou on the crank no sweat. More important are piston-to-wall clearance as measured from the spot indicated in your Bentley manual (the piston skirts are slightly bell-shaped to accomodate expansion of the piston top. Also, ring end gaps (too big allows too much pressure leakage. Too small and the ends contact, thus breaking the ring and gouging your cylinder wall). Ring side-clearance in the grooves is important because too much side gap will create too much twist in your rings and kill them.
Regarding your low compression: Standard compression ratio for turbo motors is 8.75 to 1, except for pre-APC years which is 8.25 to 1. Overboring, head surfacing,and block decking (for a nice flat surface) will all add more compression. So your mechanical compression RATIO will be more like 9.0 to 1.
JD
posted by 24.205.44...
, Thu, 21 Apr 2005 07:29:56, Thu, 21 Apr 2005 14:19:15
, Thu, 21 Apr 2005 08:13:27, Thu, 21 Apr 2005 14:21:04
, Thu, 21 Apr 2005 14:35:29, Thu, 21 Apr 2005 21:41:35
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