[Fot] Line-boring

[Fubog1 at aol.com]

In a message dated 4/18/2007 8:30:06 PM Eastern Daylight Time,  
yellow-green at sbcglobal.net writes:

Glen - I just got back from VIR - so missed this thread.  Is line  boring 
common and/or advisable for a race engine?  Other amici comments -  how many line 
bored blocks are out there??  What is actually modified to  make the rear 
seal center up after a line bore?

For an all out race engine it's SOP as part of squaring up the block but it  
shouldn't be done indiscriminately.
The housing bore has to be measured &, depending on size, it may  need to be 
honed or bored back to spec. Manufacturers usually have a range of  about 6/10 
tolerance, it's best to put it on the snug side for good bearing  shell grip. 
If it measures OK & the crank turns freely, it's most  likely OK.
The surface finish of the housing bore is critical also, it needs to be  
smooth so it makes good contact with the back of the shell. Pronounced black  
"streaks" or burnishing on the back of the old shells usually indicates a  problem 
with the housing bore.
You might have to remove a SLIGHT bit of material from the parting faces of  
the seal housing or turn down the OD of the seal housing SLIGHTLY, so it  
doesn't keep the main cap from seating properly, depending on finished size of  
seal housing register. 
If the housing bore is done properly, it won't change the crank center by  
more than a couple thou.
Glen



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