JOHN HAMILTON wrote:
>
> I'm stumped and so are all my friends. Have Volvo, B18 (1800cc) full
> race engine, Oberg filter, Accusump, baffled pan and big oil cooler,new
> high pressure pump. I'm on the third engine this year (one per race).
> Runs fine initially then eats both main and rod bearings.Engine is
> properly clearanced including endplay by a professional builder who is
> also at his wit's end. We have checked crank for straightness, line
> bored the mains, balanced and rebalanced the crank and entire
> reciprocating assembly and we still get bearing meltdown after, say an
> hour or so of racing. Assembly and reassembly are done under almost
> "clean room" conditions.Holds 80 lbs. of pressure at idle when new then
> drops when bearings start to go. Ran well at Mosport this past weekend
> and held pressure until last race when warning light went on and
> pressure was at 30 lbs. and going South. Oil temperature has been high
> at 240 - outside temperature was over 100. Oberg is full of bearing
> remains. We have also checked all passages for restrictions.There are
> approximately 7 quarts in the system. I run the engine above 7200 rpm's
> but have been doing that for twenty-five years without this kind of
> problem. Anybody have any ideas short of demonic possesion? I keep going
> back to the Oberg - cooler - Accusump circuit eventhough this setup has
> been on the car for five years without problems until this year. No
> notion is too wild. Winning idea gets team T-shirt and a percentage of
> saved psychiatric bills. Thanks in advance,
> John Hamilton
Ouch!!
I'm assuming that you have the conventional oil pump circuit -- that is,
it is in the sump and driven from the camshaft. Here are some
thought-provokers for your problem solving:
1. Forgive me in advance for saying this, since you probably check this
carefully, but do you plastigage the each crank / bearing journal as a
double check of clearances? I've seen two mysterious lube ailments
solved with this -- one, where one main journal on a crank was .010
smaller than the other ones due to a mistake at the machine shop -- the
engine would carry reasonable oil pressure for awhile, believe it or
not. The second is where a crank was mistakenly thought to be .010 under
and it really was .020, resulting in .010 clearances, and again the
engine carried oil pressure, but not enough.
2. If you want to take some components out of your lubrication circuit,
maybe one at a time, to see if it solves the problem, remember that
modern synthetic lubricants will operate satisfactorily at temperatures
in excess of 300 F -- right on up to 320 - 340 F -- so you could for
example plumb around your oil cooler to isolate that as a possible
cause.
3. Are all external lines under pressure rather than suction? Is it
remotely possible that with your plumbing circuit, some line could be
hooked up wrong and you're pulling rather than pushing oil through some
external line, allowing a leaky fitting to aereate the oil?
4. Finally, did the problem start after the installation of the high
pressure pump? Is it possible that aeration is occurring at a joint in
the pump or its attachments? Would going back to the original pump be a
consideration?
-- good luck!!
--
uncle jack
TR4 racer -- yeehaa
TR6 streeter -- hummahumma
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