Warning: coolant temp. and cracking in Rover blocks

[James Jewell <m1garand@speakeasy.net>]

All,
   Veloce just sent me a copy of their latest book for review: Power 
Tuning the Rover V8 by Des Hammil.  It's a fantastic book, and should be 
on the shelves soon.  However, it brings up some frightening points 
about the big-bore (3.9,4.0, 4.2, 4.6L) blocks.  Many of us know that 
when Rover upped the size of the bore, that the thickness of the 
aluminum surrounding the sleeves actually got thinner, which led to a 
cracking problem, with commensurate water loss into the cylinder, and 
sleeve drop.  What I didn't realize was how bad the problem was:  Fully 
25% of the big-bore blocks will develop a crack.  But it gets worse:  
For a few models, Rover installed a higher temp. thermometer in the 
engines (opening at around 185 DegF).  On those models, the cracking 
rate goes over 50%.  So the book recommends that all Rover engines run 
with the lowest temp Thermometer one can find.  The problem is that, 
with the small radiators that fit into our beloved MGBs, it's hard to 
keep the engine that cool regardless of the thermometer setting.
   Anyhow, lets do a survey:
Who is running a big-bore Rover, what is your thermometer setting, and 
are you mysteriously losing coolant?
Thanks,
JJJ

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