My Tiger had low oil pressure when hot for many years so I decided to
replace the crank bearings & oil pump. Because the engine was old I
figures that .001" undersize bearings would probably fit, so I got a set
of .001" under main & rod bearings & some plasticgage & a high volume
Melling oil pump & went to work. All the mains took the undersize
bearings & fit well, and after about 1/2 of the rods fit well I stopped
plasticgaging & put the last 4 or 5 bearings in & found that I had
locked up the engine. I found that the #8 rod bearing just was not going
to work, so I went out & got me a standard bearing for that position.
The next morning I crawled back under the car for what I expected to be
a quick finish to my project, only to find out that the standard bearing
also locked up the engine! I took the bearing out & looked in vain for
some burr or flaw in the crankshaft or connecting rod that would account
for this problem. I polished the crank, the rod & the standard bearing,
but to no avail, when I put the torque wrench to the #8 rod, the engine
locked up. I went through my old rod bearings & found that the bearings
that came out of the #8 rod were marked differently than the others. In
30 years of auto repair I've never heard of an oversize crankshaft
journal, but now I had one. I put the original bearings back into the
connecting rod & now had good oil clearance. In went the new oil pump &
everything is now happy, with my one antique bearing and a dozen new
ones. the oil pressure, that would drop to about 20 psi hot now stays up
around 80 psi with a thinner oil than I'd used before. & the old heap
sounds better. Still smokes at high rpm though. Probably needs an off
size piston to fit an undersize bore.
Doug Leithauser
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