Dirt Missile rebuild begins

[carbuff]

Originally Posted by CJD Automotive

Dry sumps are sealed systems. <snip>

Thanx for the explanation. I may block the ports on my valve covers, although everything looked good when we did the rebuild last year given my current setup. I don't have any method of de-aerating my oil, so I can see where this would be a potential problem for me...

[GregWeld]

Originally Posted by carbuff

Thanx for the explanation. I may block the ports on my valve covers, although everything looked good when we did the rebuild last year given my current setup. I don't have any method of de-aerating my oil, so I can see where this would be a potential problem for me...

To be sure Bryan — there is a connection between the top of the oil tank and your PCV system (vacuum)..... so be sure you learn about these systems to fully understand them.

[Flash68]

Originally Posted by carbuff

Thanx for the explanation. I may block the ports on my valve covers, although everything looked good when we did the rebuild last year given my current setup. I don't have any method of de-aerating my oil, so I can see where this would be a potential problem for me...

What tank are you running? My understanding is that most all tanks have some internal baffling for de-aeration purposes.

[CJD Automotive]

Originally Posted by Flash68

What tank are you running? My understanding is that most all tanks have some internal baffling for de-aeration purposes.

Sounds like a stock GM setup, which is a hybrid dry sump. If so, you need your breathers, but can be plumbed through Petersons breather can, and then to the tank.

As Greg said, if you have a pump with scavenge stages and are pulling vacuum on the crankcase, you need two additional pieces. A vacuum regulator to limit the amount of vacuum pulled on the crankcase, and a pressure pop off. Most pop offs are plumbed back to the tank. This is just a safety valve for a sealed crankcase. If the pump has an instance when it can't pull a vacuum, with the crankcase sealed, the pressure has no where to go, and usually pushes past a seal. The pop off, lets that pressure be evacuated to the tank, while still allowing the crankcase to be sealed.

[71RS/SS396]

How you plumb the topend of the engine is really dependent on the scavenge ability of the pump and whether it can maintain vacuum on the crankcase when the engine is wound up. If you can't maintain vacuum when the engine is at max rpm you have to vent the crankcase pressure to somewhere or you're going to have blow-by issues.
I started out with a 3 stage Dailey that made vacuum at idle but with the 4.125 stroke crank I have it couldn't maintain vacuum when we revved it up. I added 2 more scavenge stages, I can now maintain 15" of vacuum at 8,000 rpm and picked up 20 hp. I initially ran it sealed but with street driving I started seeing moisture accumulation in the tank oil cap and the valve covers. I plumbed a -4 line from the drivers side valve cover to the top of the tank to turn the air over and cured the moisture issue.

What I have done with the 3 stage pumps is to run one -12 line from the valve cover to the top of the tank, you can run it to the tank breather but you'll just fill with oil quicker.

[Tony V]

Originally Posted by 71RS/SS396

How you plumb the topend of the engine is really dependent on the scavenge ability of the pump and whether it can maintain vacuum on the crankcase when the engine is wound up. If you can't maintain vacuum when the engine is at max rpm you have to vent the crankcase pressure to somewhere or you're going to have blow-by issues.
I started out with a 3 stage Dailey that made vacuum at idle but with the 4.125 stroke crank I have it couldn't maintain vacuum when we revved it up. I added 2 more scavenge stages, I can now maintain 15" of vacuum at 8,000 rpm and picked up 20 hp. I initially ran it sealed but with street driving I started seeing moisture accumulation in the tank oil cap and the valve covers. I plumbed a -4 line from the drivers side valve cover to the top of the tank to turn the air over and cured the moisture issue.

What I have done with the 3 stage pumps is to run one -12 line from the valve cover to the top of the tank, you can run it to the tank breather but you'll just fill with oil quicker.

Tim, really appreciate you sharing....Greg can't wait to see some progress pics and now that you're down here in sunny AZ maybe i'll get a chance to the missile on track days. love this thread, learning what not to do and how to correct it, unfortunately it came at a cost for Greg, hang in there!

now to my question; I have a 3 stage Dailey and plumbed a -10 from valve covers into my breather line on my 3 ga tank and would usually see accumulation of oil in my breather can that would fill it 3/4 full after a full track day, is that normal?

[71RS/SS396]

Originally Posted by Tony V

Tim, really appreciate you sharing....Greg can't wait to see some progress pics and now that you're down here in sunny AZ maybe i'll get a chance to the missile on track days. love this thread, learning what not to do and how to correct it, unfortunately it came at a cost for Greg, hang in there!

now to my question; I have a 3 stage Dailey and plumbed a -10 from valve covers into my breather line on my 3 ga tank and would usually see accumulation of oil in my breather can that would fill it 3/4 full after a full track day, is that normal?

I would just run a -12 off of one valve cover directly to the top of the tank so you don't keep filling the breather tank. Are you sure you aren't over filling your tank?