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Discussion Starter · #1 ·
Background:

I recently rebuilt my ZZ502 after a distributor gear broke and destroyed some bearings.

When I did the rebuild, I replaced the oil pump with a new one of the same model that was previously installed. The pump was okay when I pulled it, I only replaced as maintenance since I was in there already. The pump is a Melling M77HV, which is their High Volume pump.

In doing my install I also added some gauges, including electronic oil pressure, so I could better monitor my new build and the like.

I did a 500 mile break-in and everything is running really well. I also installed a Holley Sniper EFI, which is also running very well, but that is another story...

I mentioned my oil pressure in passing to somebody that has much more knowledge than I do and the response was, "that seems high and you might want to look into that".

So here I am.

I have read that 10psi per 1k is pretty acceptable for the BBC and my number are high. I have also read people say this is fine. I have reached out to Melling and gotten some responses (very quickly I might add), but I am also curious as the general consensus here as well!

Details:

I am running Royal Purple 5w-20, I broke in with the RP break-in oil, which I believe was 10w-30. My pressures were basically the same between both oils as I think should be expected. I use a Mobil 1 Filter.
  • At hot idle, my pressure ranges from 38-43 or so.
  • Driving around I see in the 55-60's
  • When I get on the throttle, I see max around 70.

A few questions:

  1. Is this something I need to be worried about?
  2. Could this have been what put too much stress on my distributor gear that broke it after ~8-10k miles before?
  3. If the pressure is too high, do I have any other options that don't require me to pull the engine to replace the pump?
 

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1968 Malibu sport coupe, 489 ci. 590 hp 600 tq, RV T-400 Freakshow 3200 stall, 3.73 12 bolt posi
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That's about the same pressures my 454 had, I installed that same pump when the motor had 22,4xx miles on it and I had also replaced the RV cam for another hft cam, and NO problems, kind of wishing I used that pump on my roller 489 instead of the M77 with dark spring...but it's fine, so's yours IMHO
 

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I have almost 7K mi on my Engine that was built Jan of last year and still going strong. My pressures are almost identical to yours. I'm running Maxima 10W-30. Have run RP 5W-30 as well with same results.

Mike
 

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I just thought you were tripling down that he was good. HAHA.

Mike
 
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Ya that's the ticket.
 

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That oil pressure looks fine to me, too. What does your water temperature get up to? Does your engine run cold (160* thermostat?) Remember that your oil needs to get over ~212F to boil off moisture that invariably gets into the oil.
 

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My peanut port engine had a High Volume pump in it a couple of years ago and that engine would have 80psi cold and 40 warm but at WOT it was 80psi again. When I decided to replace the rings and bearing again I had oil in every cyl more than it should be. This time I used the std. pump now is 50 psi idle and 60 WOT. When when it comes to oil pressure more is not always better.
 

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Had my BBC Rebuilt in late 2017 // went Roller Cam/Rockers/stock Oil Pump // did the 500 Mile Breakin in early 2018
// went Racing in 2018,2019,2020 plus as much Cruzin as the Weather permits for 6 months a year here //
Valvoline Synthetic 15W40 & NAPA - NGF 1060 Filter

Just back from a little Cruz and the the Oil Preessure at Idle = 30 - 35 psi and 40 - 50 psi at higher Rpms
do not know what she does at the Track as to busy Racing and trying to beat the other guy !!
 

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All good, run it and put some miles on it.
 
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MY BBC with the same pump will hit 85PSI at 6700 RPM... and yet has around 30 at idle.
 
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Discussion Starter · #17 ·
Thanks for the input/confirmations to all that responded! It helps put my mind at easy as I drive the heck out of this beautiful machine!
 

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If you are just utilizing the electric oil pressure sensor and not a hard gauge just change the oil pressure sensor and you will get a slightly different pressure indication.
Car Vehicle Wheel Tire Hood
in my opinion a hard gauge is the only way to go with a new rebuilt engine. Even my 1965 Malibu SS came stock with a hard oil presure gauge runs 35- 60 psi all day.
 
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