oil pump question

["More Boost"]

i have read if you enlarge #2 and #3 main oil passages in the block (to crank bearings) you must use a HV oil pump. is this true? i am rebuilding a 4.1 and figured since it is apart, i might as well. i have tried the search option here but can never seem to find what i'm looking for

 

[84BuickGNYorkPA]

If you increase the flow(#2 and #3 mains) you will need more volume, or you will have lower pressure.

Chuck

 

[boostingbuick]

But you also need to open up the oiling holes in the bearings as well. I have done this with a high volume pump on my 4.1. I have set the bearings at .0015, and hot my oil pressure is 20 psi at an idle. I purchased a new front cover with a high volume pump molded into it. Very simple and worth the money. Mike has them at Full Throttle.

 

[Turbo1dr]

How can it be possible that enlarging the holes makes a engine have low oil pressure? You don't create a leak anywhere by doing it. It just allows the oil to flow "quicker" through the ports until it gets to the bearings. If the bearings have the proper clearance it will not leak past them anymore than having a standard pump in it.

The only downside I see is it makes the block weaker. It also will take slightly more time to fill up the passages when the engine is started. This is where a HV pump will make a difference.

 

[84BuickGNYorkPA]

Here is a good place to start reading..Jack Merkel Performance Engines Inc.
Jack explains why he does what, he is a engine builder on the east coast. When GM High Tech had a write up about his procedures and followed a motor through his shop he mentioned in that interview about oil pressure and drilling out #2 and #3 mains. I can't find the link right now...

I'm not here to argue with anyone, just trying to help "More Boost" get some information on his subject.

Think of it this way, and this is streched to make a point. If I hook up my pump to a 1/4" piped, loop system(closed) and I "T" into it with a gage, let's just say that I have 20 psi. Then I hook up to a 1/2" piped, loop system my oil pressure will be lower with the increase in volume. Does that make sense?

Chuck

 

[Turbo1dr]

Think of it this way, and this is streched to make a point. If I hook up my pump to a 1/4" piped, loop system(closed) and I "T" into it with a gage, let's just say that I have 20 psi. Then I hook up to a 1/2" piped, loop system my oil pressure will be lower with the increase in volume. Does that make sense?

Chuck

It should still have the same pressure. This is kinda hard to explain in writing but take a look at this drawing. If the bearing is only thing that is "leaking" due to clearances, increasing the main oil holes will not cause more leaking through the bearing. All you done was increase the volume of the pipe holding the oil.

What's really happening is...

The oil pressure unit is placed at the beginning of the oiling system so it will "see" the highest pressures before entering the engine. If the block is restrictive and you drill out all the oil passages large enough then you will get lower oil pressure at the sender. This is where people "think" they have lower oil pressures due to drilling out the mains BUT in reality it was always low at the bearings. This is because the block was creating a restriction and making the sender unit read higher than actual (at the main bearing) oil pressure.

 

[ChrisCairns]

An example....

Take a garden hose....
Put a pressure gauge into it somewhere in the middle...
Run water through it without the nozzle on it....almost zero pressure in the gauge yet lots of volume (flow) running out the end.
Now put the nozzle on it and adjust the nozzle until the water squirts the longest distance. Read the gauge now....plenty of pressure in the hose yet the volume coming out of the nozzle is a lot less than when there wasn't a nozzle. Fill a bucket both ways and use a timer if you doubt this.

What was said originally is true....

More pressure = less volume. Less pressure = more volume.

 

[BlackBandit]

If you build the engine with more clearance or use a light oil then enlarging the hole will allow more flow and therefore cause lower pressure if the pump can't move enough volume. If you build a "tight" engine then the hole won't be the restriction and the mod wouldn't be needed and neither would the HV pump.

 

[chasmat2316]

be careful drillig the mains the casting is very thin, sometime you can break thru!

 

[BlackBandit]

When I did mine I just opened up the bearing to match the block. Kind of a happy medium and it is a street/strip engine.

 

["More Boost"]

thanks for all you guys input, i am no machinist and i dont have 8K to give to merkle. and i didnt realize how thin walled that area is. so maybe i will just massage the passage and open up the bearing hole. kinda like BlackBandit did.

 

[BlackBandit]

I doubt you'll regret that. My mains and rods are both a little over .020 and I've got great oil pressure. With 5w-30 I get 23-25 at hot (after driving) idle in gear. At light acceleration and cruising speed I have 60 psi (which is what the pressure is set at) and under hard acceleration it climbs about 60. I'm going to go with a 0w-20 oil and see what pressures I get next oil change. I'm expecting similar results. (which is good because there would be more flow at the same pressure)

All I did was use the TA Perf. duel groove duel feed cam bearings, I radiused all the corners in the front cover oil passages, cleaned up all the casting flash, and opened the bearings up in the center two mains to match the block. I didn't do the end to because they only feed one rod. I also made sure the front cover gasket didn't hang into the oil passages and I have a HV pump.

 

[84BuickGNYorkPA]

thanks for all you guys input, i am no machinist and i dont have 8K to give to merkle. and i didnt realize how thin walled that area is. so maybe i will just massage the passage and open up the bearing hole. kinda like BlackBandit did.

Sounds like the way to go.... I am a machinist but, I don't have 8k for Merkle myself I just used the article as a resource for information on a turbo build. The best of luck to you with your motor.

Chuck

 

[JDEstill]

I disagree with the larger main passages = high vol pump req'd statement. Turbo1dr has it right; the oil flow is controlled by the bearing clearances a lot more than it is by passage size, if you don't increase the bearing clearances you really shouldn't be changing the pressure much.

Chris, your example is a little too simplistic. A better test would be two hose setups with the same nozzle on the end, one with a 3/4" hose and the other with a 1/2" hose. If the nozzle is only 0.1", how much of a difference is your pressure gauge in the middle of the hose going to read between the two hose sizes? It will likely be some different, but not the radical difference your experiment would see.

Anywho, I had my #2 and #3 mains drilled out, but not as big as some propose, I want to say mine were done to 5/16" instead of 3/8". I have a standard size oil pump (though with lots of porting and other mods) and I have great pressure. I've done lots of things to ease oil flow through my system, and with the logic of "more flow = lower pressure" every mod I did should have hurt my pressure instead of help it.

I'll also mention that in the references that recommend the larger mains (Power Source, Free Spirit, and Ruggles books) none of them mention using a larger oil pump, even for all out race motors. I would have thought they would recommend this with all the other oil system mods they talk about if it was truly advantageous.

Finally, I know there are some out there that have little confidence in Merkel, FWIW, apparently due to some bad experiences. I know I have never seen the recommendation for a "high vol pump req'd with larger mains" anywhere except from him. Personally I trust the other sources more than him (for the record, I have had no personal experience with him).

In my mind, rather than seeing a lower pressure at the gauge as per Turbo1dr's sketch, I think of it more this way: The spring in the oil pump housing sets the pressure at the block entrance by the gauge measuring point. If you do passage porting, main enlarging, etc... you are raising the pressure at the bearing rather than reducing it at the block entrance.

If stock you keep 60 psig at the block entrance, and there is 40 psi drop between there and the bearing (no idea what the real number is, just using that as an example), then you have 20 psig at the bearing itself. Do a bunch of porting and drill out the mains and such, and now the 40 psi drop is down to 25 psi drop. The spring is still keeping 60 psi at the block entrance, so now you have 60-25=35 psig at the bearing. More pressure at the bearing = A Good Thing.

That's what I think anyway. My thoughts are worth every penny that you paid for them

John

 

[BlackBandit]

You're pretty much right on. I hope you weren't talking about me with the larger passages = need for higher volume pump thing because that's not what I said. I said "If you build the engine with more clearance or use a light oil then enlarging the hole will allow more flow and therefore cause lower pressure if the pump can't move enough volume."

As far as the more flow = lower pressure thing goes it's correct as long as everyone understands the concept. Take the garden hose deal. If you have a hosenozzle setup that will flow 60 gallons per minute at 60 psi and a pump with the same capabilities that is pressure regulated (all with 10w-30) then every thing is perfect. If you change one thing in the system that's when the more flow = lower pressure comes into play. Let's say you put a bigger hose/nozzle on it so the hose/nozzle setup is capable of flowing 80 gpm at 60 psi. All of a sudden the pump is only able to supply 40 psi but you have 80 gpm of flow. This is why it's generally bad to run a heavier oil if you have good operating pressure. If you do that then the liquid is harder to pump so the hose/nozzle flows less at the same pressure. That means less flow across the bearings. Of course, it gives the oil pressure gauge something to do at idle when there's no load on the bearing. This is also where HV oil pumps come in. If you build an engine with looser clearances and better flowing passages and a HV pump then you can run a lighter oil and maintain good pressure with a lot more flow for better bearing cooling. Basically, pressure/flow thing only works when changing one thing at a time.

Now, if you can get the oil pressure you want with a smaller pump then its a no brainer to use the smaller pump because no matter what pump is generating 60 psi the same amount of oil will flow.

Also, you're absolutely correct about the pressure at the bearing thing. Sorry for rambling. I'll go away now.

 

[Turbo1dr]

In my mind, rather than seeing a lower pressure at the gauge as per Turbo1dr's sketch, I think of it more this way: The spring in the oil pump housing sets the pressure at the block entrance by the gauge measuring point. If you do passage porting, main enlarging, etc... you are raising the pressure at the bearing rather than reducing it at the block entrance.

If stock you keep 60 psig at the block entrance, and there is 40 psi drop between there and the bearing (no idea what the real number is, just using that as an example), then you have 20 psig at the bearing itself. Do a bunch of porting and drill out the mains and such, and now the 40 psi drop is down to 25 psi drop. The spring is still keeping 60 psi at the block entrance, so now you have 60-25=35 psig at the bearing. More pressure at the bearing = A Good Thing.

John

That makes perfect sense...sorta like this:

I would think if the oil pump was pumping all it could (like at idle) then relieving the restriction would lower the pressure at the pump and increase the pressure at the bearing. This will make the gauge read lower. So my other sketch in my previous post should have been like this:

 

[gnxtc2]

More pressure at the bearing = A Good Thing.

John

Not really. More pressure at the bearing creates more heat. You increase pressure at the bearing, you can also cause the oil to cavitate (introducing tiny bubbles). Once the oil cavitates, your engine is done. You want volume with not alot pressure.

The factory oil pumps are not efficient. Efficient pumps cost alot of money to make. Most increase oil pressure to overcome the volume issue.

Johnson's High Tech Performance

Billy T.
gnxtc2@aol.com

 

[JDEstill]

BlackBandit, turbo1dr, I think we are on the same page. I'm in total agreement with what ya'll wrote.

Not really. More pressure at the bearing creates more heat. You increase pressure at the bearing, you can also cause the oil to cavitate (introducing tiny bubbles). Once the oil cavitates, your engine is done. You want volume with not alot pressure.

Billy, I'm not sure I understand some of your statements. I don't understand why more pressure at the bearing would be bad.

First off, cavitation. How can more pressure cause cavitation? The formation of vapor bubbles happens when you lower the pressure of a fluid. For example, if you increase the flow through the system but don't change anything on the suction side passages, the oil pressure when it gets to the pump will be lower than it was before at the lower flow. That lower pressure will be more prone to form vapor bubbles. But once it is compressed the vapor bubbles go back into solution, and the higher the pressure the more the vapor wants to go away. I don't see how you can have vapor bubbles at all (unless the pump is sucking in air from somewhere, since the air won't want to dissolve in the liquid) on the pressure side of the system.

I also don't understand how more pressure at the bearing results in more heat. I did read the link you posted, thanks for that, and I can see how there is an optimum oil flow across the bearing, and flows higher than that or lower is undesirable. No idea what that flow might be for us of course. And at the bearing, pressure is flow, no doubt about that. Only way to get more flow is to increase the pressure at the bearing, or to increase the bearing clearance at the same pressure. But back to the point, when you talk about heat, I would think that starting from zero flow, as you increase flow the bearing temperature would start falling. The theory says that at some point you would get to a minimum temperature as flow keeps going up, and then from that point as flow is increased the temperature would start going up, since "the fluid is moving too fast to take away the heat". I've heard that theory applied to radiators too, and while I'm willing to listen, I don't really believe it. In the industrial heat transfer applications I regularly deal with higher velocity *always* improves heat transfer. I tend to think that maybe the temperature does go up, but not for the reason stated, that there is something else going on (something that actually does make sense ). I certainly do think that there is nothing to be gained by having more than the optimal flow and pressure.

Anyway, enough of my rambling, explain please.

John

 

[gnxtc2]

What happens when you flow coolant fast through a radiator/engine block? There is no heat transfer. What happens when the air passes through an intercooler too fast? The intercooler can't cooler the air. Same applies to the bearings, increase the pressure, you will have more flow across/through the bearings. There will be no transfer of heat when the crank spins. And the bearing heat up.

http://www.nhra.com/dragster/1999/issue06/racing_technology.html

This stuff is getting too complex.

Billy T.
gnxtc2@aol.com

 

[Turbo1dr]

What happens when you flow coolant fast through a radiator/engine block? There is no heat transfer. What happens when the air passes through an intercooler too fast? The intercooler can't cooler the air. Same applies to the bearings, increase the pressure, you will have more flow across/through the bearings. There will be no transfer of heat when the crank spins. And the bearing heat up.

NHRA: National DRAGSTER (Racing Technology) (Issue 6, 1999)

This stuff is getting too complex.

Billy T.
gnxtc2@aol.com

True about the rad and the intercooler because you are cooling one thing "through" another. The outside air has to cool the radiator fins and then the radiator fins has to cool the water inside of it. So air cools the water but has to use the radiator to do it.

The same is true for the intercooler...air cools the outside of the intercooler which now has to cool the air inside the intercooler. So air cools the air but has to use the intercooler to do it.

But for the bearings...the oil is in direct contact with the bearing and the crank so the bearing & crank should cool better with more oil flow. There is nothing "between" them that has to be cooled first.

Yes...getting too complicated for my simple mind.:redface: