The facelift on my MGA crankshaft is complete and looks fabulous. Like
magic, the rod journals are now standard size again and you couldn't tell it
from a new one. Got it all back together with new bearings and went racing
today. Drove it 135 miles from Naperville to Peoria, everything grand, and
the weather was absolutely superb. So much for the good news.
The race date lasted just 20 seconds into the first lap. Just got the engine
up to 6 or 7K rpm for a few seconds and the oil pressure dissappeared again.
Noticed the symptoms right away this time, power loss, huge drag-down
effect, got off the throttle right away. A glance at the gauge showed it
practically pegged at ZERO, then it recovered, right back up to the normal 62
psi. Race day over, I nursed it off the track and put the streeet tires back
on. No question about oil level this time, it was right on the full mark
before and after the incident.
End result is oil pressure at 800 rpm idle is now 20 instead of 50, and it
takes up to 2500 rpm to reach pressure relief at 62 psi rather than 1500 rpm.
Still runs quiet, drove it home 135 miles at 50-60 mph, no change in status,
figure the fresh crank is probably not damaged this time, just in need of a
new set of bearings.
Now the technical stuff. Fresh crankshaft, all journals reground, all sizes
perfect by the micrometer. All new bearings, correct sizes, checked by
plastigauge for correct clearance. Cleaned all inside of engine before
reassembly, checked all oil passages in block and in crankshaft. Proper oil
restrictors installed in rod journals of crankshaft. Had disassembled oil
pump for inspection, pickup tube and housing clear, screen clean, internals
of pump in good condition, cam gear OK, pump drive gear OK, pump drive tang
OK. Before starting engine, 30 seconds cranking on starter only with spark
plugs removed produced 50 psi oil pressure (yes, just at cranking speed).
So, come forth ye wisdom of the list -- puzzle of the week -- what happens to
my oil pressure at 6000 rpm?
Barney Gaylord -- 1958 MGA
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