Interesting. I have a 3A and have the same issues. Did exactly the same as
you described. My center main was worn a little more than I would like but
the journals are ready for a regrind so I did not change the mains. The odd
thing is, that at operating temperature the knock goes away and only returns
upon 1. cold start, or 2. after being shut down for a half hour or so, and
then very briefly. My oil pressure has declined a little but at 185 degrees I
have 25 at idle and 50 - 70 at speed. This is marginal at idle, but I am
told by other 3A or 4 guys that it is not unusual.
I am assuming that you cleaned the bottom of the sump before replacing?
That your oil gets dirty after 250 miles is odd.
Did you change oils? I was using Castrol 20-50 and changed to Shell Rotella
Diesel 15-40. My symptoms came immediately so I never ran the car other
than for diagnosis with this oil in it. I then replaced the rod bearings and
went to Rotella 40 Diesel. After a few hundred miles I am going to go back to
Castrol 20-50 and see what happens.
The motor runs great and cranks up to 4000 rpm and idles relatively
noislessly at temp.
This is not particularly bothersome to me other than I do not want to find
out what the issue was by looking through a hole in the block. I have used a
stethoscope to try to isolate the problem but cannot seem to locate it.
Fuel in the oil is a concern so I would give it the sniff test. The villian
here is the fuel pump diaphragm. If you have not rebuilt your fuel pump do
so right away.
You say that you replaced the rod bearings to spec. If the bearings removed
were .010 and you replaced with standard, that is your problem. Did you
check the bearing stamping on the back to be sure you were putting in exactly
what came out?
David Lylis
69 TR6 CC26160L
60 TR3A TS74461LO
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