oil type and pressure
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
oil type and pressure
Hey guys--
I have a '78 hp 300. During the break in I used valvoline 10-30 racing oil, because the cam company recommended it, due to zinc content. However, I find the oil pressure drops to an uncomfortable level when I come to stop right off the freeway. How low of pressure is TOO low?
I was wondering what type of oil you guys with older 300's use, and the viscosity.
I am thinking about 15-40 with an additive.
I have a '78 hp 300. During the break in I used valvoline 10-30 racing oil, because the cam company recommended it, due to zinc content. However, I find the oil pressure drops to an uncomfortable level when I come to stop right off the freeway. How low of pressure is TOO low?
I was wondering what type of oil you guys with older 300's use, and the viscosity.
I am thinking about 15-40 with an additive.
Elder User
Joined: Sep 2008
Posts: 563
Likes: 0
From: DeKalb, Ill.
I run Shell Rotella, 15w40. With my tired engine, the lowest I ever see
is 20 psi. That's at idle. Going down the road, I see between 40 and 50
psi. I would be concerned seeing something lower than 20 psi at a good
hot idle.
Recap- w/ engine hot,
20 psi @ idle.
40 to 60 psi @ 2000 rpm (stated in the '75 Ford shop manual).
How do your numbers compare to this?
Murph.
is 20 psi. That's at idle. Going down the road, I see between 40 and 50
psi. I would be concerned seeing something lower than 20 psi at a good
hot idle.
Recap- w/ engine hot,
20 psi @ idle.
40 to 60 psi @ 2000 rpm (stated in the '75 Ford shop manual).
How do your numbers compare to this?
Murph.
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Lead Driver
Joined: Mar 2008
Posts: 7,196
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From: Near Los Angeles
I am running 10-30. When I start the truck and it is fairly cold, been sitting for 90 minutes, I get 40 psi at idle. As it gets hot I watch the psi slowly drop and eventually get to 15 at idle, maybe 13 when coming off the freeway or just hot.
I will switch to a thicker oil like the 15-40, and see where that gets me. For a new engine to have such low psi alarms me. I know a new engine takes some dialing in, and that is what I'm doing with the oil too.
Since you have an older engine, do you run an additive in the oil?
Thanks.
I will switch to a thicker oil like the 15-40, and see where that gets me. For a new engine to have such low psi alarms me. I know a new engine takes some dialing in, and that is what I'm doing with the oil too.
Since you have an older engine, do you run an additive in the oil?
Thanks.
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
Depends on what "additive" you are inquiring about. There is EOS lube, but unsure if they still make it. There is another lube on Summit, that is recommend for engine break-in and every other oil changed thereafter. It's 11$ a quart or pint, or 98$ for a case, must be the quart then if I remember. There is also STP, blue bottle, but it doesn't have near the additive package as the original STP, red bottle. but the blue one raises the VOA of the oil.
Check on BOTOG site*Bob Is The Oil Guy*, and look at the posting there. Many, and same here will advise to stear clear of any additives unless you already have an engine that is near the end of life or are breaking-in a new engine. You could also substitute 1 qt. of Valvoline Racing 10-30(which is probably high in Zinc and maybe Calcium) in place of your 10-30 wt. package now.
BOTOG is extremely useful. I keep up to date on oil news there, since most generally all motor oil now for automobiles has reduced Zinc and Calcium, for extending the Catatlytic converter on newer vehicles. i picked up @ my local parts stores and farm stores all that was left of Power Service oil extender. It was high in Zinc and Calcium. they no longer make it now.
Anyway, best of luck
Matthew
Check on BOTOG site*Bob Is The Oil Guy*, and look at the posting there. Many, and same here will advise to stear clear of any additives unless you already have an engine that is near the end of life or are breaking-in a new engine. You could also substitute 1 qt. of Valvoline Racing 10-30(which is probably high in Zinc and maybe Calcium) in place of your 10-30 wt. package now.
BOTOG is extremely useful. I keep up to date on oil news there, since most generally all motor oil now for automobiles has reduced Zinc and Calcium, for extending the Catatlytic converter on newer vehicles. i picked up @ my local parts stores and farm stores all that was left of Power Service oil extender. It was high in Zinc and Calcium. they no longer make it now.
Anyway, best of luck
Matthew
Elder User
Joined: Sep 2008
Posts: 563
Likes: 0
From: DeKalb, Ill.
I don't know that the thicker oil would be the right solution.
I personally think that the Shell oil is better, but not because it is thicker.
Look into the info timbersteel suggested. You'll probably find much better
info there than I can offer. Something else you might want to look into;
try to get in touch with a company that sells longblocks, like Jasper. See if
they will offer any tips for engine break in oil.
Your pressure does seem a bit low when it's hot. Thicker oil might bump the
pressure up a bit, but I think it will only be masking a possible problem.
By the way, hows that thing running so far?
Murph.
I personally think that the Shell oil is better, but not because it is thicker.
Look into the info timbersteel suggested. You'll probably find much better
info there than I can offer. Something else you might want to look into;
try to get in touch with a company that sells longblocks, like Jasper. See if
they will offer any tips for engine break in oil.
Your pressure does seem a bit low when it's hot. Thicker oil might bump the
pressure up a bit, but I think it will only be masking a possible problem.
By the way, hows that thing running so far?
Murph.
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
This should have been edit, but woke up this morning realizing I mis-typed the abbreviated version for Bob Is The Oil Guy.
Should be BITOG. Just wanted to clear that up.
Should be BITOG. Just wanted to clear that up.
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Lead Driver
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From: Near Los Angeles
high volume oil pumps
I was looking into the cause and cure of my low oil pressure, and found a good write up regarding high volume over high pressure oil pumps.
In the case of engine oil pumps pressure and volume are related.
The engine is a controlled oil leak, the pump cannot develop any pressure until the volume it's putting out exceeds the volume that can leak thru the clearances. To get more pressure, it has to deliver more volume. Ultimately pressure is controlled by the volume leak past clearances and the a "relief valve". The relief valve adds to the leakage past the clearances thus maintaining a certain pressure.
Pressure is variable to the viscosity (weight) of oil used, the temperature of the oil, and the speed of the pump. Starting backwards, at idle the pump is turning slowly and pressure will be less, so much so, that when the engine is hot the relief valve is probably closed and pressure is simply established by the leakage thru the clearances. Conversely, at high speed the pressure increases because the pump is pushing more oil (volume) into the engine. At some point the volume/pressure will exceed the relief valve's spring and it will be pushed open reducing system volume and pressure. This is also affected by the thickness of the oil. Cold oil of any given "weight" has more viscosity or thickness than when hot. The thickness of the oil determines how fast both the pump can pick it out of the pan and how fast it leaks past the clearances. Thick oil results in abnormally high pressure at the pump which causes the relief valve to open. As the oil heats, it becomes thinner which is easier for the pump to pick out of the pan and it leaks faster thru the clearances. This reduces pressure and it's highly likely that the pressure relief valve will close. The same thing happens for the weight of oil in regard to leakage past the clearances and the setting of the pressure relief valve. All these variables occur at the same time.
Note that the relationship of pressure and volume is different in an engine than in a closed hydraulic system, because an engine constantly leaks oil, a hydraulic system doesn't or at least isn't supposed to leak.
A high volume pump given say a relief valve setting of 60 psi, will provide a higher hot idle pressure because of the excess volume it moves at any given speed. This is important for a competition or other hard working engine as normal idle oil pressures tend to be low and don't provide enough protection when a high load is suddenly dumped on the engine till enough RPM is built high enough to supply relief valve pressure on the system. This is a case of being able to momentarily overrun the oil supply at the bearings. The down side of a high volume pump is at high speed where there is so much excess flow from the pump the relief valve is always open to vent off the excess volume and pressure. This uses a lot engine power for no useful purpose and heats the oil unnecessarily.
A high pressure pump assumes that the volume it can deliver is far above the engines clearance leakage rate, a stiffer spring is used in the relief valve. This may prove to be an ultimate pressure that can't be achieved till the engine, thus the pump, is spinning quite fast. Again there are several variables occurring at one. Not only is the oil's thickness a concern in the ultimate pump output but so is the pumps capacity which is variable by it's operating speed and its size. Faster delivers more oil than slower. Bigger delivers more oil than smaller.
In the end pressure comes down to how much more oil the pump can deliver into the oil galleys against how fast it leaks past the clearances. Given everything above this paragraph, larger clearances leak more oil than tight clearances. This and pump wear is why a high mileage car will have lower oil pressure than when it was new. This is why or at least one reason why, a competition engine with wide clearances needs a larger volume pump to maintain sufficient pressure against the greater leakage. The other reason for a competition engine is that pressure gap between idle or dropped throttle oil pressure and the sudden need under hard acceleration, this gets into gear selection among other things. Take a road racer that comes of the corner in to high a gear, the engine has too few revs and is suddenly exposed to a fully open throttle. It's very possible that the high lugging load will blow the oil out of the rods and that the pump will not yet be supplying enough volume to make up the loss. Next thing you know it spun a bearing or worse.
For me, I build engines with excess oil pump capacity and my customers live with the slight power loss and an oil cooler. I have found over the years that this results in a lot fewer crankshaft bearing failures. I like to see about 40-45 psi at a hot idle rather than the factory's 15 to 20. For a street engine I usually pop off the relief at 60-70. Beyond that subscription to 10-15 psi per 1000 RPM above 6000 is OK. I run blower and nitrous engines about 10 psi higher in all cases since these devices can really put a lot of load on the rods and mains very quickly.
In the case of engine oil pumps pressure and volume are related.
The engine is a controlled oil leak, the pump cannot develop any pressure until the volume it's putting out exceeds the volume that can leak thru the clearances. To get more pressure, it has to deliver more volume. Ultimately pressure is controlled by the volume leak past clearances and the a "relief valve". The relief valve adds to the leakage past the clearances thus maintaining a certain pressure.
Pressure is variable to the viscosity (weight) of oil used, the temperature of the oil, and the speed of the pump. Starting backwards, at idle the pump is turning slowly and pressure will be less, so much so, that when the engine is hot the relief valve is probably closed and pressure is simply established by the leakage thru the clearances. Conversely, at high speed the pressure increases because the pump is pushing more oil (volume) into the engine. At some point the volume/pressure will exceed the relief valve's spring and it will be pushed open reducing system volume and pressure. This is also affected by the thickness of the oil. Cold oil of any given "weight" has more viscosity or thickness than when hot. The thickness of the oil determines how fast both the pump can pick it out of the pan and how fast it leaks past the clearances. Thick oil results in abnormally high pressure at the pump which causes the relief valve to open. As the oil heats, it becomes thinner which is easier for the pump to pick out of the pan and it leaks faster thru the clearances. This reduces pressure and it's highly likely that the pressure relief valve will close. The same thing happens for the weight of oil in regard to leakage past the clearances and the setting of the pressure relief valve. All these variables occur at the same time.
Note that the relationship of pressure and volume is different in an engine than in a closed hydraulic system, because an engine constantly leaks oil, a hydraulic system doesn't or at least isn't supposed to leak.
A high volume pump given say a relief valve setting of 60 psi, will provide a higher hot idle pressure because of the excess volume it moves at any given speed. This is important for a competition or other hard working engine as normal idle oil pressures tend to be low and don't provide enough protection when a high load is suddenly dumped on the engine till enough RPM is built high enough to supply relief valve pressure on the system. This is a case of being able to momentarily overrun the oil supply at the bearings. The down side of a high volume pump is at high speed where there is so much excess flow from the pump the relief valve is always open to vent off the excess volume and pressure. This uses a lot engine power for no useful purpose and heats the oil unnecessarily.
A high pressure pump assumes that the volume it can deliver is far above the engines clearance leakage rate, a stiffer spring is used in the relief valve. This may prove to be an ultimate pressure that can't be achieved till the engine, thus the pump, is spinning quite fast. Again there are several variables occurring at one. Not only is the oil's thickness a concern in the ultimate pump output but so is the pumps capacity which is variable by it's operating speed and its size. Faster delivers more oil than slower. Bigger delivers more oil than smaller.
In the end pressure comes down to how much more oil the pump can deliver into the oil galleys against how fast it leaks past the clearances. Given everything above this paragraph, larger clearances leak more oil than tight clearances. This and pump wear is why a high mileage car will have lower oil pressure than when it was new. This is why or at least one reason why, a competition engine with wide clearances needs a larger volume pump to maintain sufficient pressure against the greater leakage. The other reason for a competition engine is that pressure gap between idle or dropped throttle oil pressure and the sudden need under hard acceleration, this gets into gear selection among other things. Take a road racer that comes of the corner in to high a gear, the engine has too few revs and is suddenly exposed to a fully open throttle. It's very possible that the high lugging load will blow the oil out of the rods and that the pump will not yet be supplying enough volume to make up the loss. Next thing you know it spun a bearing or worse.
For me, I build engines with excess oil pump capacity and my customers live with the slight power loss and an oil cooler. I have found over the years that this results in a lot fewer crankshaft bearing failures. I like to see about 40-45 psi at a hot idle rather than the factory's 15 to 20. For a street engine I usually pop off the relief at 60-70. Beyond that subscription to 10-15 psi per 1000 RPM above 6000 is OK. I run blower and nitrous engines about 10 psi higher in all cases since these devices can really put a lot of load on the rods and mains very quickly.
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From: Spokane, WA
Unless you are masking an excessive wear problem, I would not use the heavier oil. 10w-30 is fine. Mine was broke in with it but after the 2nd change I went to 5w-30. Generally speaking, the lighter oil you can get away with the better...easier starts, less drag on the pump, etc.
The idiot gauge does not give one a definitive reading...you might consider going with a mechanical gauge.
The idiot gauge does not give one a definitive reading...you might consider going with a mechanical gauge.
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Lead Driver
Joined: Mar 2008
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From: Near Los Angeles
Unless you are masking an excessive wear problem, I would not use the heavier oil. 10w-30 is fine. Mine was broke in with it but after the 2nd change I went to 5w-30. Generally speaking, the lighter oil you can get away with the better...easier starts, less drag on the pump, etc.
The idiot gauge does not give one a definitive reading...you might consider going with a mechanical gauge.
The idiot gauge does not give one a definitive reading...you might consider going with a mechanical gauge.
But you know, when I had the 390 rebuilt, I had the exact same problem, and that mechanic said to go with 15-40. I did and it never idled under 20psi after that.
I suppose I'll change the Sunpro gauge to a Stewart-Warner, and see if that makes a difference.
Senior User
Joined: Jun 2009
Posts: 480
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From: Hudson,Michigan
Beware of additives that have Teflon in them.A long time ago when they first come out with teflon additives,I put it in an Opel (great little car) and right away lost 5# off my oil pressure and never got it back.It coated the bearing surfaces and made it easier for the oil to escape.I don't even know if anything like that is out there anymore.I have never seen much good come from additives and a fresh engine should not need them.I have also heard of lifter problems stemming from certain additives.Todays oils are pretty high quality and I think the biggest thing is getting the oil there to do the job and that is usually mechanical.
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