<VV> VirtualVairs Digest, Vol 60, Issue 102

[djtcz at comcast.net]

----- Original Message ----- 

From: Les < corvair at mts.net > 
Subject: <VV> Engine building - more bearing clearances 

OK, as a result of all the good advice, I gave up trying to measure 
bearing bores with my crappy tools. I assembled and torqued the block 
and crank first with .001 US then with .002 US, and settled on .002 US 
as that gave me clearances of .0015-.0020 right across. 

Now to the rod bearings. Plastigauging with STD bearings I see about 
.002 clearance. Books say .001 best, .003 max. For a stock 140/4sp 
street engine that likely won't see more than 3000 miles a year, do you 
suppose it's worth $100 and a week out of my schedule .................. 
Thanks, 
Les 
=============================================== 
First I'd use my telescope gauges and mike to measure each of the rod bores in 6 locations, practicing 100 times to get readings consistently within a half thou, The a bearing ID installed in a rod. 
I'd use the "wring thru once " method with the telescope gauge lock lightly snug. 
http://bbs.homeshopmachinist.net/archive/index.php/t-27178.html 

Then for fun I'd "calibrate" that package of plastigage using 2 stout square steel bars with dressed faces, separated by feeler gauges and squeezed in a bench vise. 

Only then would I decide whether to buy other bearings. 

I would prefer a real 2 or 3 over 1 unless I KNEW the rod bores were gorgeously round and taper free. A little extra clearance is much more forgiving of housing/bearing distortion.