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I found this strange bit

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jlaird

jlaird

Great Pumpkin
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There is a bolt/cap cover that goes on the out side of the over oil pressure spring at the rear right side of the engine.

I have one that has had a hole drilled in it and taped. There is a screw through it with a lock nut, on the inside is welded a plunger that would allow you to compress the spring thus increasing the oil pressure pop off protection.

Any clues guys, I have never seen anything like this before, have you? /ubbthreads/images/graemlins/hammer.gif
 
Jack, a typical racers trick to make an adjustable oil pressure relief valve. You can actually buy them, but most of us made our own. David Vizard mentions them in his "A Series" book.
Jeff
 
Knew what it was for, had never seen one. Now I need a raceing engine I guess.

Beep beep, Bugeye comming through.
 
From aptfast.com

oprv-adj.jpg
 
I do this to all the engines I build. Note, the ones that are made with the big knobs won't clear the gear reduction starters.
 
Do you supose they use a special spring, and if so how do you identify that.

Mine seems to be home made, but nice and has an allen head bolt.
 
The standard ones are colour-coded. No clue of how/what the racing ones are ID'd but: I'd guess they use the "stock" springs too.
 
I just got a new spring and installed it, don't remember it being any particular color. I must have at least 3 others all seem to be different lengths, intresting. And that is why I got a new one.
 
The Mini crowd uses the Cooper-S spring with about 3-coils cut off its free length and instead of the standard plunger/valve, we use a CV joint ball bearing (9/16" I believe).

The adjustable relief valves are nice and let you dial in the pressure but keep in mind they won't correct low idle speed oil pressure. That's only addressable during an engine rebuild.
 
Yes, understand that you could only kick the run oil pressure up or down a bit and that bearings, mostly cam effect the idle pressure.
 
Doug just jogged a synapse with that ball-bearing comment. Must be thirty years since I'd seen/heard of that!

Weird.
 
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