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Oil Pump Shims?

Old 12-15-2014, 04:41 PM
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Default Oil Pump Shims?

Alright guys, my motor is already built and running but looking back at things I'm wondering if I made a mistake with this. I got a Street/Strip High Performance Oil Pump Stock Pressure (~60PSI) from Boundary Engineering.

I have the following
.002 rods and mains
5W-40 oil
kept my squirters
added an oil cooler

Should I have added a shim to my oil pump? If so, what's the easiest way to do this? I don't have excess noise that I can tell, but BPs are pretty loud anyway. I've converted my dummy OP gauge to a real one, so I know pressure is steady, but it doesn't give me an actual number.
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Old 12-15-2014, 05:32 PM
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I've been wondering a little on the value of increasing the bleed pressure. I got a shim added in my build but as I have rationalized, the shim only increase the max pressure of the cold thick oil to make sure to replenish oil film everywhere with a thicker oil and tighter tolerances.
I.e. higher max pressure (usually seen when cold).

When up to some heat the shimming should not have any role to play at all (pressure below the bleeding pressure), or have I misunderstood the oil pump function?
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Old 12-15-2014, 07:14 PM
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Stock b series massively overpressurise as is.
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Old 12-16-2014, 12:18 AM
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Originally Posted by Mazdaspeeder View Post
Should I have added a shim to my oil pump? If so, what's the easiest way to do this? I don't have excess noise that I can tell, but BPs are pretty loud anyway. I've converted my dummy OP gauge to a real one, so I know pressure is steady, but it doesn't give me an actual number.
It's probably fine. Pick up a cheap oil pressure gauge and stick it in temporarily to check?


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Old 01-26-2015, 09:50 PM
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I'm pulling my oil squirters and while I'm in there I'd like to shim the oil pump as well. I'm on street/strip pump too. My oil pressure is a tad over 65 when cold or over 2k rpm when warmed up. I'd like to be closer to 80 for the old rule of thumb 10psi for every 1k rpm. I contacted BE and they emailed back .1" = about 6 psi. I'm going to add about .200" worth of shims to get me to my desired pressure. I just don't want to go too far and cause a problem with the relief not being able to bleed off enough.

I've read a few other places where BE has added 2 shims or recomended it. Can anyone verify if those 2 shims are each .100"? Or does anyone know what thickness they are? I forgot to ask.

FYI their exact quote was:
"The shimming is easy enough to procure for yourself. Its roughly .1in per 6 PSI. The bore of the relief valve is 16mm, so any washer that is just a big smaller then 16mm will work. Take the pin out, (careful the spring is pre-loaded), put the shims on the carter (or retainer if equipped), and then reinstall the carter pin. Should be all that needs to be done."
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Old 01-27-2015, 06:13 PM
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I'm curious why you might think 65psi hot isn't enough. Pressure is volume in versus clearances letting oil out. Just like boost pressure, oil pressure is a measure of volume versus resistance of flow. Increased pressure above what is needed to lubricate the engine will create a little additional heat, wear on the pump, and wear on the crankshaft flats that drive the pump, nothing major, but it will rob horsepower. Volume is more important than peak pressure.
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Old 01-27-2015, 06:46 PM
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FWIW, I thought about doing this, and I may, but I don't think it will make much difference. I did some searching online and found some youtube videos of some seriously powerful race engines on a dyno, and they were running oil pressure in the 60's at full tilt, which granted was around 6K but these were nelson-racing engines..... 4 digit HP BB twin turbo engines.

That said, in theory if the car has 100 PSI oil pressure when cold at 1,500 and say 20-30 at 1,500 when warmed up, why? If the bypass opens at say 60, then it should bypass at 60 and never go over, but they do go over. This makes me think the bypass can't bypass enough oil when cold to get the pressure down.

This may be a problem, or a feature. Too much oil pressure could be bad at startup I guess, but since pressure is a measure of restriction, maybe since cold oil doesn't want to flow, the engineers designed the relief valve to only bypass so much, so even when it's fully opened, only so much oil can bypass when cold.

I don't know, haven't looked at a miata oil pump, but I will before I assemble mine. I guess I'll post back with better info when I do, but for now, this is something to think about.
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