Paul Baker wrote:
>
>....the oil pump was replaced for a new D. Welch h/c pump (due to excessive
>wear in the gears of the std BJ8 pump) and the cam, valve springs, seals and
>bucket followers were replaced (valve guides were fine). Overall the engine
>was in very good condition.
>
>
>The problem is that the oil pressure since the rebuild and is now 3 bar (45
>psi) on cold tick over and 1.8 bar (26 psi) when hot. I can't see that this
>is going to improve greatly when I replace the 10-40 with the 10-60. My
>engine rebuilder is somewhat baffled by this outcome. We plan to check the
>oil pressure relief valve but this was not touched during the rebuild but what
>else could be causing this problem?
>
>As always, any suggestions greatly appreciated.
>
>Paul
>
>
Paul,
Could it be that the D. Welch h/c (high capacity?) pump has excessive
internal clearance or is a different type pump. Gear pumps are capable
of generating higher pressures than say a rotary vane pump.
Also, in a great article written by Tim Studdard and J.K.Jackson
published in the January 2005 Issue of Classic Motorsports, the authors
state "every 0.001 inch clearance between the inner and outer rotor will
cost 10 psi of oil pressure".
You may need to open the pump to check clearances.
Alan
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