Result is what I would expect - 70 cold should not a problem, but dont run it
at 4krpm till it warms a bit.
A coil spring exerts a pressure proportional to the compression. So by
compressing the spring more when seated, you require a higher pressure to move
it of the seat. You are simply moving its operationg point up the pressure
curve.
Ideal 3k rpm hot would be 55ish, 1k idle hot would be 35ish.
Robert N. Blair Yellow 65BJ8 RNBmail at yahoo.com
--- On Sat, 4/30/11, Bob Spidell <bspidell at comcast.net> wrote:
> From: Bob Spidell <bspidell at comcast.net>
> Subject: [Healeys] Pressure relief valve
> To: "healeylist" <healeys at autox.team.net>
> Date: Saturday, April 30, 2011, 7:16 PM
> Background: my BJ8 has run low oil
> pressure at idle for as long as I've had it. At startup I
> get 60psi, but after running on hot days I would register,
> for all intents and purposes, zero psi at idle. In spite of
> this, the engine has run and performed well for me for over
> 100K miles. I use 20W-50 dino oil.
>
> There has been a lot of discussion on the BCF about
> replacement relief valve springs being shorter than
> spec. It has been suggested that putting washers or
> other shims or a 1/4-inch bolt behind the spring could
> increase running pressure. I actually didn't believe
> it because AFAIK the valve is there to keep pressure from
> getting too high, and presumably would be fully closed at
> normal running pressure. But, I was curious ...
>
> So today I pulled the relief valve and measured the spring
> at 2 & 11/32"; quite a bit less than 'spec.' So I
> installed the 1/4-inch bolt and fired her up; 70psi on cold
> start/fast idle--not too surprising. What's surprising is
> even after the engine has warmed-up--when I would normally
> see 10-20psi, before a long run in hot weather--I am getting
> 40psi. And the max pressure is still at 70psi; so the effect
> is max pressure is up 10psi, but the hot idle pressure could
> be up 10-20psi!
>
> My questions to the forum are: is 70psi too high a max oil
> pressure? Any explanations for this phenomenon? Should I
> split the difference with some shims? Go back to the
> spring-only setup so I can sleep?
>
> Bob
>
> --
> *******************************************************************
> Bob Spidell
> San Jose, CA
> bspidell at comcast.net
>
> *******************************************************************
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