A correctly working oil pump will provide huge amounts of pressure, working
out low pressure readings is a process of elimination. First of all I would
put all original stuff in place without any spin on conversions or oil
coolers and check the paper oil filter isn't collapsing. Check the pressure
at 2000 rpm, cold it should be at least 75PSI. Fit a washer or two to space
the oil pressure relief valve spring and check the pressure has gone up,
(I've seen 120PSI, it is OK for a short time). The car then needs to be
driven for at least ten miles to get the oil up to temperature and then the
pressure should be 40-60PSI at 2000 rpm. As long as the engine isn't revved
above say 2500 rpm then low oil pressure isn't an issue for testing purposes
and no damage will result (as long as there is some oil pressure). Things I
have come across resulting in low pressure are collapsed oil filters, oil
pump rotor too short, sticking pressure relief valve, incorrect size
bearings/crank (I've even seen a packaged set of bearings with different
sizes), loose main bearing cap bolts, scored main bearings with crud from an
engine rebuild
John Kipping
----- Original Message -----
From: "MARK J WEATHERS" <markjwea@email.msn.com>
To: <fot@autox.team.net>
Sent: Monday, December 30, 2002 1:36 AM
Subject: TR6 Oil Pressure Relief Valve
> Amigos,
>
> Here is a practical problem to divert us from the ongoing legal debate:
>
> I have an oil pressure problem in my fresh TR6 engine that is limiting the
> pressure to 50 psi max. I suspected the oil pump and in the process of
> replacing it decided to test the pressure relief valve that unseats and
dumps
> oil back to the suction side. I don't know if this is a common design but
it
> consists of a plunger under spring pressure that seals off the return
passage
> from the main gallery.
>
> The only way I could test it (engine in the car with oil pan and pump
removed)
> was to apply air pressure to the return port in the block, which is the
> reverse of the actual relief valve flow in operation. I did this and was
able
> to detect slight air leakage back into the main gallery through the bypass
> valve. If it leaks in this direction it will surely be as bad or worse
with
> actual pressure working to unseat the valve. I now think my oil pump was
okay
> after all (no threat of libel lawsuit, I worked on the pump myself).
>
> Some important background: When I built the engine I replaced the stock
> plunger with a part I made in our machine shop because the original was
worn
> on the shaft. I reamed the housing to the new shaft size and made the
'head'
> thicker to effectively shim the spring. I also bought the stronger spring
from
> Moss but did not use it. I suspect that I have screwed this up somehow
(not
> the first time but I can't resist trying to 'improve' things when I have
them
> apart). What I don't understand is that I lapped the new plunger into the
> block with coarse grinding compound and I do see a witness mark all the
way
> around. The lapping mark isn't as deep as I would like as it is hard to
rotate
> the plunger to lap it in, but I am sure the angle and concentricity of the
> sealing suface is good.
>
> My options that I can see:
> 1. lap it some more
> 2. put in a stock plunger and housing
> 3. Pull the motor and recut the seat $$$$
> 4. Plug the return port, pipe the return flow out of the side of the block
to
> an external relief valve and into the oil pan
> 5. Hope someone in FOT has seen this before and can help me before the
event
> next weekend!
>
> Anybody out there have any experience with this, Kas, anyone?
>
> Mark
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