FWIW:
I recently purchased a booklet by J. W. Huffaker on "Competition
Preparation for the MGB."
Concerning the crankshaft it says:
"The standard crankshaft is adequate in strength for competition use. It
is advisable, however, to make some modifications to insure good bearing
life and increased crankshaft life. When crankshaft speed above 6500 rpm
is required, it is advisable to cross drill and groove the crankshaft to
give full oil feed to the number two and three rod journals, as
illustrated in figure I. On the standard crankshaft, the main bearings,
numbers 2 and 4, are not drilled. They are fed oil through the cylinder
block gallerys but do not, in turn, feed the intermediate rod bearings.
This is adequate for normal use for speeds up to 6500 rpm. To further
increase the strength of the crankshaft and give a harder and better
bearing surface, the crank should be first ground to .006" undersize
then nitrited by a COMPETENT heat treater and then reground to .010"
undersize. This will allow you to correct any error in index or size at
this time. A crank treated in this fashion will give excellent Service
and should last several seasons of racing if given reasonable care. The
finished grind on the crankshaft should give a rod bearing of to .0025"
and the main bearing clearance of to .()()3". The standard B.M.C.
bearings are made by Vandervell and arc cxccllent for competition usage.
The part numbers for these bearings arc listed in our parts list under
Item HAE 286-rod, and HAE 287-main. Reworked crank shaft is HAE 285."
That means reground MGB crankshafts are satisfactory.
Does it also imply that the twin cam crank could be reground if properly
prepared as above?
Blake
/// or try http://www.team.net/cgi-bin/majorcool
/// Archives at http://www.team.net/archive
|