engine breathing

[356mal]

this is my first go at a dry sumped motor and I have a couple of questions re relieving the pressure from the top and bottom end of the motor .
I have searched the pictures and info on this forum and cannot find a definitive answer.
the hole in the block near the fuel pump .
should there be a hose from this hole to relieve
the bottom end pressure ?
if so what size ID hose and where does it go to ?
into the catch tank or the dry sump oil reservoir ?
or should it be blocked off ?
the same question for the hose from the valve cover
what size ID?
where does it go to ?
and the overflow spout from the dry sump oil reservoir
does it go straight into the catch tank ?

1600 cc kent formula ford motor

thanks

mal

[Purple Frog]

Many dry sump systems use the oil pump to create a vacumn in the crankcase. In that case you don't want any openings into the crankcase other than the oil scavage lines running to the pump.
The tube running from the valve cover to the catch tank is usually restricted inside with a plug that is drilled out with a small hole (~1/8").
The drysump tank is vented to an oil catch tank.

[kea]

PM sent.

[t walgamuth]

I don't know if this is a contensious point or not. I see Keith has responded by PM.

On my car the hole next to the fuel pump was connected to the valve cover but neither was vented to the atmosphere. This pressurized my crankcase and forced oil out my front pan seal. When I noticed that I vented the valve cover to the oil resorvour and plugged the hole next to the fuel pump.

Since the oil is a closed system I don't see how You can take in more than you put out, so I don't understand how you can create a vacuum there nor why it would be desirable.

[alangbaker]

I don't know if this is a contensious point or not. I see Keith has responded by PM.

On my car the hole next to the fuel pump was connected to the valve cover but neither was vented to the atmosphere. This pressurized my crankcase and forced oil out my front pan seal. When I noticed that I vented the valve cover to the oil resorvour and plugged the hole next to the fuel pump.

Since the oil is a closed system I don't see how You can take in more than you put out, so I don't understand how you can create a vacuum there nor why it would be desirable.

The reason it's desirable is simple: lower air pressure means lower air resistance.

Even though it's not a big loss, if there is air in the crankcase, then the rotating parts of the engine expend some power overcoming drag. Lower the air pressure and you reduce the loss and get more power to the rear wheels.

[DaveW]

...Since the oil is a closed system I don't see how You can take in more than you put out, so I don't understand how you can create a vacuum there nor why it would be desirable.

In addition to the previous post, there is a consensus that lower crankcase pressure enhances ring sealing and also reduces oil getting into the combustion chamber, both of which improve HP.

Also, it is done quite often. A larger than necessary scavenge pump creates the low pressure, and excess gasses are vented from the dry sump to the atmosphere through the breather.

[Roux]

The scavenge rotor should be larger than the pressure rotor and both are turning at the same RPM so the scavenge must pump some gas as well as all of the oil that the other guy delivered. So you get to make some vacuum if you have a restrictor between the head and the crankcase and the crankcase is sealed off properly. The vent to the tank should therefor only be routed from the rocker cover. Both pumps are positive displacement devices so the math works. All of this assumes typical side mounted pump.

[Bob Posner]

My Titan was vented from the hole at the mechanical fuel pump when I bought it. First weekend it put a pint of oil into the catch tank each 20 minutes. Jay came by and plugged the hole and said to never vent there as the fuel pump lever arm throws the oil out. Next session the catch tank had a couple ounces, via the valve cover vent. I assume an electric pump would reduce the output if in fact the lever is the culprit?

[Roux]

Bob,

Once you go to venting only the top of the engine I doubt the ounces of overflow are related to the fuel pump. I Could be wrong. Perhaps you just had a few ounces more oil in the system than ideal? A few ounces in the overflow per session is just assuring you that you had the level right at the maximum it can handle and are being safe when it come to making sure you don't starve the engine

[t walgamuth]

how is the restriction created between the head and the crankcase? ...and what size hole is then preferred?

[Brian]

There is no restriction between the head and the crankcase, they are vented to each other by the oil drain holes built into the head and block. What I do is vent the top of the engine at the valve cover to the dry sump tank, and then vent the tank to the over-flow tank. You should only get oil in the over-flow if the tank is getting pressurized significantly (excessive blow-by past the rings, and rebuild time), or it's either too full or poorly baffled.

Gas/vapour in the crank case comes mostly from blow-by past the rings. If you are aggressively evacuating oil and vapour from the crank case, the engine can be designed to use lower tension rings with less drag. The larger the engine, the bigger the scavenge section compared to the pressure section, to the point where large V-8 engines use four or five scavenge sections. Pinto engines use two or three scavenge sections.

Brian

[356mal]

thanks everyone for your replies

I am going to blank off the hole behind the fuel pump
and run a 5/8" hose from the rocker cover to my catch tank,
when the motor comes out next I will drill a hole in my
oil reservoir and re-route the 5/8" hose.
it is a big job to get the motor out and it has to come out to get the oil reservoir
out I cant drill the oil reservoir in situ
so I will just top up the small amount as necessary
I will run a small hose from the oil reservoir tank to the catch tank

thank you everyone
I have learnt a lot today

mal

[stephen wilson]

I believe you can use a check valve in the valve cover vent to build vacuum, while still letting any positive pressure escape.

[T644HU07]

Many dry sump systems use the oil pump to create a vacumn in the crankcase. In that case you don't want any openings into the crankcase other than the oil scavage lines running to the pump.
The tube running from the valve cover to the catch tank is usually restricted inside with a plug that is drilled out with a small hole (~1/8").
The drysump tank is vented to an oil catch tank.

If the valve cover is vented to the atmosphere via the oil tank/overflow tank wouldn't this prevent a vacuum from being created?

There is no restriction between the head and the crankcase, they are vented to each other by the oil drain holes built into the head and block. What I do is vent the top of the engine at the valve cover to the dry sump tank, and then vent the tank to the over-flow tank. You should only get oil in the over-flow if the tank is getting pressurized significantly (excessive blow-by past the rings, and rebuild time), or it's either too full or poorly baffled.

Gas/vapour in the crank case comes mostly from blow-by past the rings. If you are aggressively evacuating oil and vapour from the crank case, the engine can be designed to use lower tension rings with less drag. The larger the engine, the bigger the scavenge section compared to the pressure section, to the point where large V-8 engines use four or five scavenge sections. Pinto engines use two or three scavenge sections.

Brian

I am not aware of any FF oil pump that has two or three scavenge sections; please enlighten me!

I believe you can use a check valve in the valve cover vent to build vacuum, while still letting any positive pressure escape.

Hey, this is a great idea!

Has anybody hooked up a vacuum gauge to the sump to see how much of a vacuum can be achieved?

[Art Smith]

a picture to answer some of the questions............

Art
artesmith@earthlink.net

[Craig Henry]

After reading one of the earlier posts today, I thought to myself, “Art Smith should post an image of his testing set-up.” And he did.

Craig

[T644HU07]

a picture to answer some of the questions............

Art
artesmith@earthlink.net

Nice photo!
What are the two pipes on the rear of the block for? The one on the right side appears to drain oil from the #4 - #8 pushrod holes. Is this correct? The one on the left side appears to be attached to the gallery that feeds the main bearings but I can't see where it goes to.

[EACIII]

This is why I love the Kent over the Honda. There are all kinds of thoughts and ideas on how to make the most power. The Honda is just a dumb plug in unit.

Ed

[Art Smith]

Nice photo!
What are the two pipes on the rear of the block for? The one on the right side appears to drain oil from the #4 - #8 pushrod holes. Is this correct? The one on the left side appears to be attached to the gallery that feeds the main bearings but I can't see where it goes to.

thanks! more text and photos on the subject can be found in my post on lubrication sub-system preparation:
http://www.apexspeed.com/forums/showthread.php?t=42317

the right tube on the rear supports the four rear cylinder head drains (also used for push rods)
the short answer is: the supply side of the oil pump!

Art
artesmith@earthlink.net

[problemchild]

This is why I love the Kent over the Honda. There are all kinds of thoughts and ideas on how to make the most power. The Honda is just a dumb plug in unit.

Ed

This is why I love the Honda over the Kent. There are all kinds of thoughts and ideas on how to make the most power. The Honda is just a dumb plug-in unit.



Now that the Runoffs are visiting the West, I'm hoping we will see all Art's expertise and hard work in action!

[t walgamuth]

a picture to answer some of the questions............

Art
artesmith@earthlink.net

My car had a pressure equalization hose between crankcase and valve cover but no vent to the atmosphere. It pushed out the seal at the front of the pan and leaked oil. I vented it to the atmosphere and patched the hole and stopped leaking oil there.

[t walgamuth]

a picture to answer some of the questions............

Art
artesmith@earthlink.net

Is there vent to atmosphere on this engine?

[Art Smith]

Is there vent to atmosphere on this engine?

Tom-

the simple answer is yes! when pressure in the crankcase exceeds ambient, the check valve opens venting the crankcase to the catch bottle at the rear. pressure in the crankcase higher than ambient is the problem. the only source of pressure higher than ambient in the crankcase is ring pack blow-by and it's the REAL problem because it represents lost horsepower!! to complicate things a little further, it's important to recognize that pressure in the crankcase is ambient plus blow-by minus excess scavenge. think of excess scavenge as the difference in swept volume of the pressure section and the scavenge sections, both are positive displacement pumps whose net displacement per unit time increases with rpm. side mount four and five port pumps have very little excess scavenge so engines using them are prone to crankcase pressure build-up and are therefore almost always vented to the catch can with NO check valve. pressure build-up in the crankcase causes oil to be driven out through/around seals AND adversely impacts ring pack sealing performance.

I've found crankcase pressure to be an extremely perceptive metric for assessing ring pack performance and health. to the point I only use leak-down testing to fault isolate situations where there's a known problem. on a dyno, crankcase pressure provides a real time metric to assess ring pack performance as a function of rpm. the Kent's common crankcase prevents individual cylinder monitoring. cross plotting horsepower, crankcase pressure, and rpm is an insightful technique for determining if your ring pack is providing optimal sealing where the engine will be used.

Art
artesmith@earthlink.net

[t walgamuth]

Tom-

the simple answer is yes! when pressure in the crankcase exceeds ambient, the check valve opens venting the crankcase to the catch bottle at the rear. pressure in the crankcase higher than ambient is the problem. the only source of pressure higher than ambient in the crankcase is ring pack blow-by and it's the REAL problem because it represents lost horsepower!! to complicate things a little further, it's important to recognize that pressure in the crankcase is ambient plus blow-by minus excess scavenge. think of excess scavenge as the difference in swept volume of the pressure section and the scavenge sections, both are positive displacement pumps whose net displacement per unit time increases with rpm. side mount four and five port pumps have very little excess scavenge so engines using them are prone to crankcase pressure build-up and are therefore almost always vented to the catch can with NO check valve. pressure build-up in the crankcase causes oil to be driven out through/around seals AND adversely impacts ring pack sealing performance.

I've found crankcase pressure to be an extremely perceptive metric for assessing ring pack performance and health. to the point I only use leak-down testing to fault isolate situations where there's a known problem. on a dyno, crankcase pressure provides a real time metric to assess ring pack performance as a function of rpm. the Kent's common crankcase prevents individual cylinder monitoring. cross plotting horsepower, crankcase pressure, and rpm is an insightful technique for determining if your ring pack is providing optimal sealing where the engine will be used.

Art
artesmith@earthlink.net

Yeah, my engine is a five port with no check valve that I can see and its vented to the res and the res is vented to the catch bottle.