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Discussion Starter #1
I just had the bottom end of my olds redone (twice), I am pretty sure the machinest didnt allow for "looser" clearances, and I spun a bearing 5 minutes into the test run. The pressure never dropped (40-75)until I idled it down to do a basic check for leaks ect. (up to this point I was jazzed !!!!, all the vitals were perfect and it ran GREAT! ) when I shut it down, I smelled burnt oil and the pressure dropped to almost zero. I towed it in and tore it down, all but a few of the rods and mains were toast
So i didn't go back to the same builder, The shop I went to this time has alot of experience with the marine olds motors, lucky for me I shut it down before any damage was seriously done, he ended up mic'ing it/polished the crank, straightlined it, and re-size the rods, I took It out sunday and it ran and did great, but when I shut it down the oil pressure at idle dropped from 40 psi (cold) to 20 (warmed up) at idle, and would jump right back up to 50-60 psi when I accelerated.
I have a standard oil pump in it, and now rather than see what happens I am going to change it out. Mellings has two different pumps one is high "volume", the other high "pressure". Summits description of the "pressure" pump mentions for looser tollerences, but the "volume" pump, would have been my logical choice. I have already installed 2 drainback lines one each side for the oil return from the heads to the pan (hardlined),enlarged and matched the oil drainback passages from the heads into the block, polished the valley, de-burred any obstructions so hopefully the oil can get back to the pan quick enough.
So my question is ......wich pump should I go with, the high pressure or high volume ?
Thanks,
John
 
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I just had the bottom end of my olds redone (twice), I am pretty sure the machinest didnt allow for "looser" clearances, and I spun a bearing 5 minutes into the test run. The pressure never dropped (40-75)until I idled it down to do a basic check for leaks ect. (up to this point I was jazzed !!!!, all the vitals were perfect and it ran GREAT! ) when I shut it down, I smelled burnt oil and the pressure dropped to almost zero. I towed it in and tore it down, all but a few of the rods and mains were toast
So i didn't go back to the same builder, The shop I went to this time has alot of experience with the marine olds motors, lucky for me I shut it down before any damage was seriously done, he ended up mic'ing it/polished the crank, straightlined it, and re-size the rods, I took It out sunday and it ran and did great, but when I shut it down the oil pressure at idle dropped from 40 psi (cold) to 20 (warmed up) at idle, and would jump right back up to 50-60 psi when I accelerated.
I have a standard oil pump in it, and now rather than see what happens I am going to change it out. Mellings has two different pumps one is high "volume", the other high "pressure". Summits description of the "pressure" pump mentions for looser tollerences, but the "volume" pump, would have been my logical choice. I have already installed 2 drainback lines one each side for the oil return from the heads to the pan (hardlined),enlarged and matched the oil drainback passages from the heads into the block, polished the valley, de-burred any obstructions so hopefully the oil can get back to the pan quick enough.
So my question is ......wich pump should I go with, the high pressure or high volume ?
Thanks,
John
Never never never never go with a high volume pump in an Olds for a marine application. The deal with Olds is they pump all the oil to the top end too quickly and run out of oil in the pan and it runs out of pressure. There are a few mods you can do to an Olds that are almost necessary to make them work right in a boat. The drainback lines are a good first step. Do a search, I’m sure someone will post a link soon.
 

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mo balls than $cents$
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mondello(sp?) restricted pushrods would be a smart upgrade bout now;) pull the pump back off the motor and shim the bypass spring till you have a oil pressure you're comfortable with :)bulb
 

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I'm No Expert
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3,139 Posts
Unless you where standing on it and drained the pan in that 5 minute test you where going to have problems regardless if it was in a boat or car.

Hi vol pumps i always read were for motors setup with larger clearances, with the extra clearance the motors flows more oil, the hi vol pump keeps the system full/pressurized.

Hi Pres pumps i dont really know anything about, i would like to learn more about them though. In my head right now i'm thinking maybe hi pres pumps are really for motors cranking out serious amounts of hp to help keep the rod and crank from tagging the bearings? This is my THEORY

How big is your pan btw?
 

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B.A.M aka "Black Azz Mike
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High pressure is needed BUT high volume is NOT needed in an olds application. Get a set of restricted pushrods or just install pipe cleaners(chep fix) in your old ones.
 

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www.highflowdynamics.com
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Every Olds 455 engine that comes through the shop with a rod kicked out of the pan has at least one thing in common: half-grooved main bearings. Every time.

Every Olds 455 engine that leaves the shop as a fresh rebuild has at least one thing in common: fully-grooved main bearings. We have zero Olds 455 come backs and we contribute this to the the fully-grooved main bearings.

LO
 

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Discussion Starter #8
I will give yo a quick rundown on what I have done to date, first I detailed the valley and opened up the drainback holes in the heads and if you look right under the top right head bolt hole, a section af the block is ground back (follow the head gasket line, where the hump is, that actually used to be just a hole for the oil drainback)

Here is how it normally looks

Then the return lines


I also had the guys drill smaller holes in the cam bearings prior to installation as my oil restrictors (sorry didnt get a chance to get pics of them.
I am not sure what other mods I can do but I thank you all for the input, I am going to pickup a new high pressure pump, and take it from there.
Thanks again for the tips.
 

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I am not sure what other mods I can do but I thank you all for the input, I am going to pickup a new high pressure pump, and take it from there.
Thanks again for the tips.
Just to give you a hard time bud...:)bulb... YOU CAN BUY A CHEVY MOTOR!
Sure does look pretty on the stand. I'll have my old cell phone back tomorrow night...I'll call you.
 

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E-7 Sheepdog (ret)
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Never never never never go with a high volume pump in an Olds for a marine application.
Smart advice.

There is nothing wrong with 20PSI hot idle oil pressure and 50-60PSI revved oil pressure.
Stock oil pump here too.

My 454 runs that going on 4 years now.
 

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I took It out sunday and it ran and did great, but when I shut it down the oil pressure at idle dropped from 40 psi (cold) to 20 (warmed up) at idle, and would jump right back up to 50-60 psi when I accelerated.

So my question is ......wich pump should I go with, the high pressure or high volume ?
Thanks,
John
First of all, the pressures you quote sound pretty normal, the warm oil will flow better than the cold and therefore the lower pressure at idle. I believe the rule of thumb is 10 psi for every thousand RPM.

If you put in a high pressure pump and run the same type oil, you will likely see the same pressure at idle, and a higher pressure at speed. Basically a high pressure pump has a stiffer regulator spring so the pressure bypass in the pump won't open until the higher pressure. At idle, the pressure bypass in the pump is closed and you pressure is a result of wt and type of oil, the bearing clearances and engine speed.

If you want to boost the idle oil pressure, try different wt oil, try synthetic oil, etc.

Just my $.o2

Doug
 

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Retired Air Force
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940 Posts
I just bought a Melling oil pump (M-77) and I believe it to be a standard pressure and volume pump. It did come with a spring that you could use to increase pressure if you desire. I stayed with the stock spring. I believe less is more when it comes to oil pumps. Why have the extra strain on the cam gear when it is not necessary?
 

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Sit N' Spin
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hil:)hil:)hil:)hil:)hil:)

Reality Band Aid!! ;)
Since when is running a much better designed part in place of a poorly designed one considered a band aid?
 

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John (dozzer) bummer re the Olds,sounds and looks like you did most every thing you could or was recommended to you . We use a "reworked" standard volume pump ,large capacity pan (10 qts or better) ,restrict the push rods (roll pins) ,stock brg clearances , improve oil return flow, 15 40 rotella and hi quality filter ,hot OP will usually maintain around 50 psi ,25 to 30 at idle Tom
 

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Highaboosta
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I assembled the short block for my bro-in-laws Olds 455 W30 a couple years ago and found that the rod side clearance was only .002
I had the side of the rods ground to give the clearance that the Mondello book specified.
I believe that the tight side clearance caused a bottleneck in the oil flow even though the oil pressure read plenty high on the gauge.
It had spun the rod bearings in the car and that was what lead to the rebuild.
With any Olds I would check that as a possible common oil flow problem area.
 

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Since when is running a much better designed part in place of a poorly designed one considered a band aid?
Fully grooved main bearings are just a cover up for a problem somewere else in the oiling system that should/could be fixed....that's all. ;)
But that's just my opinion.:)sphss

Your saying a fully grooved main bearing is a good design and a partial groove is a poor one?????hil:)hil:)hil:)
 

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I agree with Warp Speed.I've run partial grooved bearings in my olds for years with no problems.I set the motor up a little loose,spent a lot of time on oil drain back. restricted push rods,stock rods that were machined according to mondello's book, 8qt. pan and balanced the motor.I take it to 5000 at least once every time it gets wet.55 psi oil pres at 3000, 35 at idle. I think alot of the problems with olds are incorrect machine work and assembly.
 

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NW Spectraholic
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If you don't like that hot idle pressure you're gonna need the hi-volume pump. I run them in all my Oldsmobiles with no worries. I also hog out the upper bearing shell in a mill to match the large oil hole in the block. No other restrictors, cut the side slots on the rods and the drainbacks in the heads are drilled out. And all this with only an 8 qt pan! ;)
 

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Discussion Starter #20
Thanks for all the input, good stuff :D
I am going to restrict the pushrod tubes, and I picked up a mellings high volume pump, with the high pressure spring, I also got a Mobile filter, and I (as always) am using Valvoline racing 40 wt. oil. The oil thats in it now still looks like new and I have only ran it enough to figure out I am not comfortable with this pressure. I took it out again last friday and "babied" it until it warmed up and it was right at 10 pounds at idle, but 40 at 3,000 rpm. I personally just think the "loose" rods and mains are letting the oil escape before it gets to the top end and a little more volume will fix it right up. I am pulling the motor tonight and installing the new pump.
again thanks for the input, I'll keep you posted with the results.
John
 
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