dry sump questions

[Fordman]

For an FE application what would those in the know recommend for a oil tank size?. Can someone also explain the differences/advantages of 3/4/5 stages dry sump pumps?. I am only assuming it is nothing more than the amount of plumbed pickups in the oil pan?. Any other recommendations are appreciated...John

[blykins]

The size of the tank depends on the application:  drag race, road race, pulling truck, etc. 

The number of stages is the number of scavenge points plus the "push" side.  So for instance, if you have 3 pickups in the pan, 1 from the lifter valley or valve cover, and then a pressure side, then you have a 5 stage oil pump:  4 sucks and 1 blow. 

Some pumps are strong enough that they will act as a vacuum pump as well, so you can have 3 pickups in the pan, 1 scavenge point in the lifter valley, and then a point that acts as a vacuum point.  That would be a 6 stage pump. 

[Posi67]

Are you building the first Comp Eliminator FE John  

[Dumpling]

There are SERIOUS packaging considerations involved.
Have you seen/measured a 5-6 stage pump. 
Do you know where you're going to put the tank (in the passenger compartment)?
And then all the hoses/plumbing...

[jayb]

I've been running a six stage on the SOHC in my Shelby clone for the last several years.  Three pickups in the pan, one at the back of each head, plus the pressure stage.  I was told by the dry sump folks (Peterson Fluid Systems) that this would give me plenty of crankcase vacuum.  That turned out to be BS, it will deliver some vacuum at idle but not when the engine starts running at higher engine speeds.  I was always able to get 15 inches of vacuum with my GZ Motorsports vacuum pump.  For the cost, weight, and complexity of the dry sump system, and no crankcase vacuum to speak of, I'm very disappointed in it.  I'm going back to a normal FE oil pump and pan, a vacuum pump, and an accumulator (Accusump) to ensure oiling under all conditions.

[cammerfe]

I plumbed an Accusump into my street FE more than 15 years ago. As part of the starting procedure I'd trip the solenoid, watch the pressure come up, and hit the start button with max pressure showing. With the Holley EFI and a good hot Mallory ignition, it'd start instantaneously. When I'd pull the bearings, they almost looked like new.

KS

[blykins]

There are SERIOUS packaging considerations involved.
Have you seen/measured a 5-6 stage pump. 
Do you know where you're going to put the tank (in the passenger compartment)?
And then all the hoses/plumbing...

All of that is good truth.  It's a very large package and the fittings/hoses are -12 and -16 usually.....and are not cheap.   This engine has over $1000 in fittings/hoses alone.





BTW Jay, I've seen dry sump pumps from Aviaid/Peterson pull up to 15-16 inches of vacuum with no external vacuum pump.  Are you sure you don't have a way that air is getting in somewhere?

[jayb]

If I had an air leak, why does my GZ vacuum pump pull 15" on the same engine?

[blykins]

Good question.   

Where is the GZ pulling from?  Same spot?

[jayb]

No, it is pulling from the valve cover since it only has one vacuum inlet. 

[blykins]

Hmm.  Trying to think of what the difference would be.  On some of the pulling truck engines, the dry sump pumps can pull so much vacuum that the owners are advised to allow some air in when not running hard so that some oil can get to the wrist pins and other areas. 

[jayb]

Peterson has told me that there are some engines where they just don't get a lot of vacuum.  That is why they are now offering a Star vacuum pump as an add-on to the dry sump systems.  I just spoke with a Super Stock racer over the weekend and he's had the same experience as me.  Maybe big block vs. small block or something?  Regardless, no more dry sump for me...

[scott foxwell]

Hmm.  Trying to think of what the difference would be.  On some of the pulling truck engines, the dry sump pumps can pull so much vacuum that the owners are advised to allow some air in when not running hard so that some oil can get to the wrist pins and other areas.

If you're scavenging a lot of oil then the "vacuum" that a dry sump will produce will be minimal. Dry sump systems are not made to create crank case vacuum. If you get some as a byproduct, that's just a bonus. The more oil in the scavenge lines, the less vac it will pull. I pulled 14" on the 611 BBF I built with very leaky (Chinese) valve covers but we ran one scavenge to the valve cover strictly for vac. Had three in the pan, one in the lifter valley and one in the valve cover. Owner of the engine added a vac pump and went to 22", picked up 40hp on the dyno. Some pumps are also better than others and there are different rotor designs. "Starving the wrist pins" is an old wives tale. In a race deal you really can't pull "too much" vacuum. If you're getting 80% barometer you have a very well sealed up engine. If you're galling wrist pins, it's not from the vacuum, but that's another discussion all together.
I agree with Dumpling...plumbing and packaging is a big concern with dry sump systems. I would never depend on a dry sump for vacuum unless you're using one stage dedicated for that. Also, a dry sump has it's own challenges and is not a bolt on cure-all for oiling system issues. A good wet sump design is a lot simpler and can serve the oiling needs of any engine if set up right.

[blykins]

Sometimes the wives' know what they're talking about though.....

Pulling a lot of vacuum on the crankcase can wick oil away from the wrist pins and other areas.  Switching to a DLC coated tool steel wrist pin with .002-.0025" clearance will usually curb it, but high amounts of vacuum can cause wear there.

[scott foxwell]

Sometimes the wives' know what they're talking about though.....

Pulling a lot of vacuum on the crankcase can wick oil away from the wrist pins and other areas.  Switching to a DLC coated tool steel wrist pin with .002-.0025" clearance will usually curb it, but high amounts of vacuum can cause wear there.

The only way vacuum will pull anything away form anywhere is if you have a big leak and you're creating an air stream through the engine. Evidence of that is a lot of oil in the breather/catch can. If the engine is sealed up and all you're doing is creating a depression, then there is no air movement...nothing is going anywhere, nothing is being sucked off of anything and the catch can will stay relatively dry. Usually what happens is; with more vacuum, we have more potential rpm and more power...light weight wrist pins, lack of clearance, poor piston design...all start showing their ugly little heads when they get pushed a little harder and things start flexing a little more. Heavier wall wrist pins, coatings, better piston design and/or a little more clearance usually solve the problem but it's not from oil being taken away. Fix those problems and run as much vacuum as you can. It frees up a LOT of power. I have a customer with a 1K HP BB Chev that he drives on the street regularly and pulls 22" hg, usually 15-18 cruising. Going on 5 yrs now. Engine turns 8K when he wants to. Plenty of other similar examples. If oil starvation was the problem, more clearance wouldn't help. I think .002" is a little excessive, but it might be what it takes if wrist pins are flexing or pin bores collapsing. If the parts are good, clearance is usually not an issue. I usually run .0010-.0012 on the rods and .0009 -.0010 in the piston (cold). Little more on big power stuff. Never ever had a wrist pin issue.