Oil Pump And Windage Trays

[Todd L.]

I have two questions:
1.) What is the difference between a standard volume, a high volume, and a high performance oil pump? What is the benefits/ drawbacks to one over the others?

2.) What is the difference between a windage tray and a stock baffle? Again what are the benefits/ drawbacks to one over the other?

My 74' L-4 is currently bored .030 over it may have to go .060 I have not been to the shop yet, but I would like to work the heads and cam it, while keeping the exterior stock looking. I believe the stock intake will be a major limiting factor, only being able to reach power to about 5500 rpm.

Thanks

Todd

[Joe R.]

Re: Oil Pump And Windage Trays

I have two questions:
1.) What is the difference between a standard volume, a high volume, and a high performance oil pump? What is the benefits/ drawbacks to one over the others?

2.) What is the difference between a windage tray and a stock baffle? Again what are the benefits/ drawbacks to one over the other?

My 74' L-4 is currently bored .030 over it may have to go .060 I have not been to the shop yet, but I would like to work the heads and cam it, while keeping the exterior stock looking. I believe the stock intake will be a major limiting factor, only being able to reach power to about 5500 rpm.

Thanks

Todd

Hi Todd,

I did the research on here related to oil pumps for my L72. I came to the conclusion the standard volume, standard pressure pump is the way to go for me. I will only be running on the street. The high volume / pressure comes at a cost, wasted horsepower! Why does your engine need more pressure than stock? It will judge better with a standard pressure pump, too.

The windage tray is a relatively flat piece of metal that sits over the middle of the oil pan. A baffle would be a divider built into the oil pan that helps control oil sloshing around during hard acceleration, etc.

You're on the right track with the head work. That's where the "free" power is! Head work may get you a few extra RPM's, too. I would recommend against a cam change, unless you're going racing. GM really knew what they were doing when they designed these engines for the street. A cam change will likely affect judging too. Get the Federal Mogul (Speed Pro) camshaft from your local NAPA dealer. Plus it will be Parkerized and may not need the break in procedure required by Comp Cams and probably others.

You may already know this, but don't let the machine shop deck the block. That will wipe out the numbers and broach marks on the pad.

I would also recommend managing your compression ratio. Take the needed measurements before any machine work is done to the block. Does it detonate now? One way to manage the compression ratio is by choosing the head gasket thickness.

Joe

[Todd L.]

Re: Oil Pump And Windage Trays

Joe,
Thanks for the help. One of the reasons I was asking about the pump was, when i got the car the motor was supposedly rebuilt within the last 500 miles. What I found was three of the valves were stuck, the pushrods were bent and broken, I found pieces in the lifter valley and one piece actually made it into the oil pan. So the whole motor is being taken apart and looked at. I would like more hp than the 270 stock. I don't know if oil was a problem or the builder did something wrong. I was thinking of going with larger valves and a port and polish of the heads since, I am sure things are hosed up.

Todd

[William C.]

Re: Oil Pump And Windage Trays

In my experience with '74 cars, a huge improvement in performance is to be found in the distributor just by returning the curve to a mid-60's configuration. Carb jetting is an issue also. Chevrolet did all kinds of tricks to meet emissions regs (which changed every year) in those days at the lowest cost possible. That resulted in "hiding" a lot of horsepower to meet the federal tests. Do the easy things first after your rebuild and you may be surprised at how it perks up.

[Robert K.]

Re: Oil Pump And Windage Trays

Bill,
Emissions were measured based on volumn of gas consumed. So, if you burned more fuel you could pollute more. Talk about wrong headed, leave it to politicians to screw it up.
Bob

[Terry M.]

Re: Oil Pump And Windage Trays

Bill,
Emissions were measured based on volumn of gas consumed. So, if you burned more fuel you could pollute more. Talk about wrong headed, leave it to politicians to screw it up.
Bob

Just like alcohol in today's gas.

[Tom P.]

Re: Oil Pump And Windage Trays

For MANY years there has been debate back and forth about stock vs hi-vol oil pumps in engines. Which is the best choice? I DO NOT have the answer to which engine should or should not get which pump.
BUT, what I DO KNOW is that during a rebuild, EVERY engine of mine gets a hi-vol pump---------------even the grandma grocery getter type engines. PERIOD.
In 40+yrs of building and running engines with hi-vol pumps I've had ZERO problems.
Back in the late 70s when I built the healthy 350 for the 56, I wanted a hi-vol pump but also wanted to retain the stock 56 oil press gauge. I discussed this with several people and even considered having the 56 oil gauge modified for a higher pressure indication. Well, I crossed my fingers and gave it a try. Ran that engine up through the 80s with the stock gauge and hi-vol pump. Once the oil was heated up and normalized, the gauge stayed between 55 and pegged.
In the late 90s I built the SB400 that's in the 56 now. It has a hi-vol pump. The gauge still sits between 55 and pegged. Still NO problems--------------------with either the engine or the stock 56 oil pressure gauge.
So, that's my position on hi-vol pumps-----------I'm sticking with it.

[Domenic T.]

Re: Oil Pump And Windage Trays

With normal clearances on the crankshaft I have found the stock pump to be all that was needed. I do use tha larger pump in place of the stock at times but find that if you want more preasure you can put another bypass spring in the pump or simpply shim the spring as we did in the 50's & 60's with a washer.
We wanted more preasure/volume to make sure that # 1 & 2 journal on the crankshaft did not starve for oil at high RPM's.
If your not going to have the revs high for long periods of time the stock pump with good oil is just fine.

DOM

[William C.]

Re: Oil Pump And Windage Trays

Only issue I have seen is that high pressure high volume pumps have the capability of emptying the sump in a 5 quart pan if the oil level get's about 1/2 quart low. Fortunately learned that at no cost.

[Duke W.]

Re: Oil Pump And Windage Trays

Oil pumps are positive displacement type pumps, but once the pressure relief valve opens, excess volume is just shorted back to the inlet, but the excess volume takes power, which means fuel, and it heats up the oil. They offer no advantages on a reasonable road engine - just disadvantages.

If you have a loose-clearanced vintage SB built for racing that needs 80-100 psi at 9000 revs, a high volume, high pressure pump is the way to go, but current NASCAR engines run as little pressure as possible to make the engine live - only 30-40 psi in order to minimize oil pump parasitic power.

The normal vintage SB OE pump with a 40-45 psi relief valve is perfectly adequate for any normal road engine configuration, but GM did increase the pressure relief spring to 55-60 psi (using the same standard volume pump as other 327s) on late '63 mechanical lifter engines, and this carried through '65. These cars have 80 psi oil pressure gages.

The SB oiling system is well proven and very reliable. All bearing problems I have seen can likely be attributed to running the oil pan dry, usually due to a combination of low oil level and high dynamic loading, such as autocross or road racing. Severe oil starvation can seize a bearing, which will usually result in the rod bending/breaking about one-third to one-half the way up from the big end.

High revving mechanical lifter cam engines were equipped with the larger oil pans to stave off oil starvation because the higher the revs, the tougher it is for the oil to get back to the pan, and the windage tray helped prevent the rotating assembly from frothing up the oil.

On and engine that does not rev beyond about 6000 the smaller pan is fine, but the oil should be kept at or even a little above the full level if you autocross, road race, or run canyons at nine-tenths.

Back in the sixties I ran my mid production 327/340 SWC that had the same oil pump as 327/250 HP (standard volume, 40-45 psi relief spring) several hundred miles on road racing tracks and had no problems, but I did run the oil level a quart over, which was a "trick" that road racers used back then to prevent oil starvation before SCCA allowed dry sumps in the seventies.

I also watched the oil pressure gage as much as possible. Fluctuations in oil pressure can mean the pump is sucking air.

Duke

[Todd L.]

Re: Oil Pump And Windage Trays

So a high volume oil pump increases the pressure of the oil? What is the relief valves for?

Thanks for all the information.

Todd

[Domenic T.]

Re: Oil Pump And Windage Trays

The preasure reliefe valve determines the amount of oil preasure. It is adjusted by spring tension on the valve.


DOM

[Chuck S.]

Re: Oil Pump And Windage Trays

So a high volume oil pump increases the pressure of the oil? What is the relief valves for?...

Gear pumps put up NO pressure unless they have a resistance to pump against; they will pump as much flow as possible at the maximum rpm of the driver.

Once resistance has been provided, a gear pump will provide as much pressure as possible against that resistance...if the pump is blocked in (infinite resistance), it will simply burst the containing vessel or piping, twist off the drive shaft, or bog down and stop the driver. The relief valve insures that some minimum flow is maintained to eliminate mechanical failure.

The relief valve spring is sized to relieve at a set pressure, which also equates to a design minimum flow with established resistance on the pump discharge and design pump speed. In this case, the established resistance to the discharge flow is set by the bearing clearances. Other factors including oil temperature and viscosity also affect the discharge pressure...if your oil is too viscous when cold to flow through the bearing clearances without overloading the pump, the relief valve maintains constant discharge pressure by bypassing oil back to the pan. More flow equal more cooling, but consumes excessive horsepower (reduced performance and fuel economy).

Duke is telling you that GM engineers did a good job figuring out how to get adequate cooling and lubrication on a street engine without consuming excess horsepower.

[Duke W.]

Re: Oil Pump And Windage Trays

What Chuck said...

Also, OE replacement pumps, which are all "standard volume" are available with both 40-45 psi relief springs, and 55-60 psi relief springs for the later mechanical lifter 327s that used them.

"High volume" pumps are strictly aftermaket. They were never used for any OE SB engine, and AFAIK all these aftermarket high volume pumps have relief springs in the 60 psi range or higher range.

If you don't understand how the oil pump works - as Chuck explained - do some archive searching as it has all been explained in great detail.

It's important to understand the concept of a "constant volume" pump which is what the oil pump is and how the pressure relief spring works to limit mechanical stress on the pump while still providing sufficient oil volume to the engine.

Up to the point the pressure relieve valve opens, full output volume is delivered to the main oil gallery. Once the valve opens, flow to the main gallery is controlled by the input pressure, which essentially means that oil delivery volume is constant with increasing RPM, and excess oil from the pump, which increases approximately linearly with pump speed is bypassed by the relief valve back into the pump inlet.

A high volume pump will achieve full pressure before a standard volume pump does, but beyond this point, the HV pump is just using extra HP to churn and heat up the oil. Some HV pumps deliver full pressure at idle speed, which is totally unnecessary.

An OE pump with a 40-45 psi relief spring should idle at about 20-30 psi with fully warmed up oil depending on idle speed and oil viscosity and achieve the 40-45 psi by about 2000 RPM.

The high pressure OE pumps will idle at about the same pressure - actually on the high end on high-idle speed mechanical lifter engine and achieve the 55-60 psi by about 2500.

Duke

[Joe R.]

Re: Oil Pump And Windage Trays

Todd,

Back to your question about the windage tray, this thread has some good pictures of one:

https://www.forums.ncrs.org/showthre...=2667&uid=6292

Joe