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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: Challenger 1]
#1236815
05/23/12 12:48 AM
05/23/12 12:48 AM
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Joined: Apr 2003
Posts: 959
Cincinnati,Ohio
jcastle1
super stock
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super stock
Joined: Apr 2003
Posts: 959
Cincinnati,Ohio
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Since then I have built 3-340s 2 440s, a couple of diesel engines, and some motorcycle engines. Not to mention many BAE hemis.
Does that help any?
I drove my latest 340 at Bonneville at near wide open throttle for over 5 miles at a time with a standard oil pump and it held up fine in 95 degree weather, twice that day with no oil pressure problems. That's a serious workout at wide open throttle for miles at a time.
So,am I killing my combo by running a high volume pump(Melling)on my 383 with a 9 quart pan?
Nearly 90 at startup,and 60 when fully hot.
I have oil restrictors in the heads.
If so,I will order a stock pump tomorrow.
When I put this combo together I had a choice between stock,hi-pressure,or hi volume.
I chose hi-volume based on the info I had at the time,and knowing I had a deep pan.Keep in mind,my car is a street car that i tnt sometimes.However,I always drive it like it's a racecar.
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: jcastle1]
#1236816
05/23/12 01:23 AM
05/23/12 01:23 AM
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Joined: May 2003
Posts: 6,562
Downtown Roebuck Ont
Twostick
Still wishing...
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Still wishing...
Joined: May 2003
Posts: 6,562
Downtown Roebuck Ont
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I think some folks need to brush up on basic hydraulic theory  . How old is this 440? You said the oil was black. If this is an original untouched engine I will bet that the pickup is full of nylon timing gear teeth and petrified valve seals. Just as an after thought, check the hex drive shaft to make sure it isn't stripped at one end or the other and slipping under the added rpm load. Kevin
Last edited by Twostick; 05/23/12 01:25 AM.
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: CUDA8U]
#1236818
05/23/12 02:28 AM
05/23/12 02:28 AM
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Joined: Aug 2003
Posts: 43,190
Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,190
Bend,OR USA
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Quote:
it's a rebuild from about 5 yrs ago, low mileage,i bought the car from a second owner who knew very little about it,he had a few bills laying around from the previous owner.
as i posted before, why would the oil pressure drop so rapidly from 3300rpm to 3500 and beyond?It will hold at 70psi all day until i get up around 3500 then it drops.What's triggering a rapid drop within a couple hundred rpm...i would think the oil pressure should gradualy drop with rpm increase.Wouldn't the pan be be gradually sucked dry instead of as described?
I would pull the oil pump drive gear and look at the tip, if it is rounded that is probally the problem. I'm assuming the oil pressure rises with the revs until it starts dropping oil pressure, is this correct? If so maybe the drive is toast now   Eliminate one thing at a time  The other thing is the bypass spring opening early and staying open above the threshold opening pressure  BTW, what about the oil pan ? Is it a 402 or some other stock oil pan or is it a after market deep pan? Prying minds want to know   
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: jcastle1]
#1236820
05/23/12 08:07 AM
05/23/12 08:07 AM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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Quote:
Since then I have built 3-340s 2 440s, a couple of diesel engines, and some motorcycle engines. Not to mention many BAE hemis.
Does that help any?
I drove my latest 340 at Bonneville at near wide open throttle for over 5 miles at a time with a standard oil pump and it held up fine in 95 degree weather, twice that day with no oil pressure problems. That's a serious workout at wide open throttle for miles at a time.
So,am I killing my combo by running a high volume pump(Melling)on my 383 with a 9 quart pan?
Nearly 90 at startup,and 60 when fully hot.
I have oil restrictors in the heads.
If so,I will order a stock pump tomorrow.
When I put this combo together I had a choice between stock,hi-pressure,or hi volume.
I chose hi-volume based on the info I had at the time,and knowing I had a deep pan.Keep in mind,my car is a street car that i tnt sometimes.However,I always drive it like it's a racecar.
NO! I wouldn't do anything at this point,don't worry! HV pump is fine just as long as it's not losing oil pressure and your only going to have that possibilty at hi RPMs. It'll be fine I'm betting.
Like Dogdays said, I think the OP should pull his oil pan and inspect his bottem end expecially his pickup and the distant from the bottem of the pan.
My
I do think also like somone said, HV pumps are a gimmick and I have not used them for many years and I have not lost any motors due to oiling problems. The less power it takes to turn the oil pump the better because for one thing the distributer is affected by the drive flexing under load.
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: 70Cuda383]
#1236822
05/23/12 08:22 AM
05/23/12 08:22 AM
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Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
Challenger 1
Too Many Posts
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Too Many Posts
Joined: Feb 2005
Posts: 28,312
Cincinnati, Ohio
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1 litre is approximately 1 US quart . . .
yup 1.05668821 quart
I know that. but my point was that at 5 liters, or 5.28 US quarts, he's got enough oil in the pan.
I disagree...
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: Cab_Burge]
#1236827
05/23/12 03:01 PM
05/23/12 03:01 PM
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Joined: Jun 2003
Posts: 21,434
It's a dry heat
gtx6970
Too Many Posts
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Too Many Posts
Joined: Jun 2003
Posts: 21,434
It's a dry heat
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my bets on the pickup is to close to the bottom of the pan.
What makes you think that? I run the stock pickups on the bottom of the pan like the Mopar FSM recommends, no problems ever  Car runs low tens, high nines shifting at or above 7000 RPM on every run with the stock 3/8 pickup and 6 quart Mopar OEM pan for the 1970-71 Hemi/440 6 pak motors, 5W 20WT Valvoline non synthetic Take a hard look at the stock pickups and go from there
pickups tubes are adjustable, and if they are to close to the bottom of the pan it will cause exactly what the op described.
makes no difference what kind of pan or pickup,it needs clearence to pull lube in under it
to high in the pan will do the same thing , as it'll start sucking air
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: jamesc]
#1236828
05/24/12 04:43 PM
05/24/12 04:43 PM
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Joined: Jan 2012
Posts: 489
NE
bigtail
mopar
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mopar
Joined: Jan 2012
Posts: 489
NE
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Quote:
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I think some folks need to brush up on basic hydraulic theory
talk about an understatement
some people seem to think a HV pump has the power of a black hole 
What I seem to remember, is that a 1/2" line will only flow 20 gpm, no matter what. You cannot physically force more fluid through a 1/2" line. That being said, wouldn't a HV pump strain more and actually cause Horse Power losses, because it is trying harder to force that 1/2" line? Up and until it breaks at the weak link, the pump driveshaft? School me if I am wrong, as I have been known to be before. Many times. Or does the pressure relief spring come into play and just bypass everything? (even the bypass has a size, though) Even still, it seems you are trying to drive a square peg into a round hole, and it will cause increased friction, heat and mechanical wear.
This page is made up completely of recycled electrons.
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: bigtail]
#1236829
05/24/12 07:42 PM
05/24/12 07:42 PM
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Joined: Jan 2003
Posts: 5,875
communist bloc of new jersey
jamesc
master
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master
Joined: Jan 2003
Posts: 5,875
communist bloc of new jersey
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Quote:
Or does the pressure relief spring come into play and just bypass everything?
yes that is the case. if i get time i'm going to lay out a number of different pumps, take pictures and give explanations of how the system works. i'm not sure of the maximum flow through a 1/2" line but i was once discussing this with a very intelligent engineer while we were discharging electrolytic hydrogen into a unit at (iirc) about 3000 PSI through a 1/2" line. as he explained i believe there is a certain "wall" that has to do with velocity in that regardless of how much pressure is applied it won't flow any more but i'm not certain.
in reality none of that applies with regards to a oil system because we're not talking large flow rates or pressures.
pressure is the driver of flow, in a given system the greater the pressure applied the greater the flow regardless of the pumps volume capacity. a stock pump set at 80# will flow more oil through then engine than a HV pump set at 60# as long as the stock pump achieves the 80#.
a high volume pump will take more power to drive because it's doing more work.
what so many people don't seem to grasp is that regardless of what pump is being used from a stock pump up to a titan or dry sump if the pressure observed in the engine is the same than the flow is the same.
anything not being used is internally circulated through the pumps bypass.
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: CUDA8U]
#1236830
05/24/12 08:18 PM
05/24/12 08:18 PM
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Joined: Dec 2008
Posts: 2,782
USA
JoesMopar
master
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master
Joined: Dec 2008
Posts: 2,782
USA
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surely someone has had a stock pan and hv pump with this problem before,
Yeah.....that was me... 
383, stock 4 quart pan, windage tray, HV pump, 440 Source Heads. The drainback sucked.
so what solved the problem for you?
Getting rid of the HV pump. The only thing that would be different is the 440 source heads, which do not drain back nearly as fast as the stock heads. The point is all I had to do was swap the pump.
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Re: OIL PRESSURE DROPPING AT HIGHER RPM
[Re: JoesMopar]
#1236833
05/24/12 09:19 PM
05/24/12 09:19 PM
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Joined: Jan 2003
Posts: 5,875
communist bloc of new jersey
jamesc
master
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master
Joined: Jan 2003
Posts: 5,875
communist bloc of new jersey
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Quote:
The volume going through the 1/2" pickup is not the "limiting factor"...it's the flow rate. The HV pump moves more oil through the system....think of it as a vaccum. The increased capacity of the pump creates a stronger pull on the pickup. That's why you're getting more pressure from the HV pump, the flow rate is higher...but, the stock pump isn't going to run at a higher psi than an HV pump unless you have something wrong with your system or the relief spring is partially open.
please don't be offended but this is wrong. the HV pump will only move more oil through the system if it's output pressure is higher and depending on other factors it may not have any higher pressure than the stock pump. unless the engine is so loose the stock pump cannot supply enough oil as long as the relief valves are set at the same pressure the flow through the engine will be the same.
again if the stock pumps relief is set a 80# (and the pump is achieving 80#) and the HV pump is set at 60# than the stock pump is pumping more oil through the system than the HV pump.
the increased capacity of the HV pump ONLY pulls harder on the suction if it's discharge pressure is above the stock pump, otherwise the oil is internally recirculating from the pumps discharge back into the suction through the relief cavity.
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