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bleed shim vs bleed hole

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Simple math proves that a bleed shim gives much more mv bypass with reduction of shim surface area vs a bleed hole.

Alot of expert tuners and home tuners seem to group these two strategies together in their mental models.  They might seem similar in application but are totally different in results, yet many say they prefer one over the other, why?

I have experimented using both individually and together simultaneously.

 

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Bleed shim action will depend a lot of the piston ports area. With huge ports I don't see a way to do anything good with a bleed shim.

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A bleed hole acts differently, much more progressive. It's very small usually, 1-2 mm so trying to shove oil through it at high speed doesn't work well. The bleed shim sorta self adjusts as the stack is pushed open. 

Kinda hard to explain, but they are different.

edit; You can get purpose made bleed shims with little slots in them to control area if it's needed. Or you could simply grind a little notch(s) into a shim to do the same.

Edited by DEATH_INC.
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On 5/23/2020 at 2:08 PM, DEATH_INC. said:

A bleed hole acts differently, much more progressive. It's very small usually, 1-2 mm so trying to shove oil through it at high speed doesn't work well. The bleed shim sorta self adjusts as the stack is pushed open. 

Kinda hard to explain, but they are different.

edit; You can get purpose made bleed shims with little slots in them to control area if it's needed. Or you could simply grind a little notch(s) into a shim to do the same.

Shit,

The idea of grinding a little notch has never occurred to me.

 

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