Creating a good vacuum for the crankcase....

[Maltman]

Well, as I have this thing apart to get ready for a leak down, I notice that the oil galleys are not aligned well at all. I have stock unmodified heads and are original (along with the block).

In my mind, this seems like it could be a very big issue if I'm having any significant crankcase pressure building up. Since the galleys aren't free to flow (about 60 percent of the head provision is blocked by the block), the oil would puddle in the heads and create problems (like it already has) with breathers and valve cover gaskets.

I imagine the factory didn't see this as a problem and it probably wasn't with stock boost levels....but now that I have more than doubled the engineered boost levels, I'm suffering.

I'm really toying heavily with making up some sort of vacuum kit that will eliminate the pcv to throttle body setup and simply pull a vacuum on the engine at all times. I've been looking at electric versus mechanical and they don't seem to be comparable.

It would be easy to add a mechanical pump since my AC pump is no longer used and it would provide worry free operation. If I'm figuring things right, I could tap the original pcv hole for the vacuum and run it through a vacuum reserve (to compensate for any larger leaks that may be larger during wot 1/4 mile blasts) with a oil collection canister/filter to deal with the oil vapors/acids.

As a result, we could maintain around 15" of vac on the case at all times and never have to worry about the dreaded oil getting into the intake or blowing gaskets or simply blowing oil out the valve covers. Also, creating a gauge to measure/monitor the crankcase pressure would help in preventing any future issues with oil leaks if pressure leaks overcome the system. Since most of us eliminate the factory "vacuum" pump (valve cover to turbo evac line), many of us suffer from the excess pressure and vapors.

Anyone with any insight or experience with this area or the vacuum pump setup would be greatly appreciated! The engineering of the mechanical system might take some work, but an electrical system would be fairly simple....so I think

Let me know what you think

 

[pwr.slave6]

evac system

Check out white racing. scroll down on there front page
these guys rock in s.e. MI.http://www.whiteracing.com

 

[bruce]

As a result, we could maintain around 15" of vac on the case at all times and never have to worry about the dreaded oil getting into the intake or blowing gaskets or simply blowing oil out the valve covers.

The *slick* way is going to a dry sump oiling system, and overdriving the pump, so that it draws a vacuum.

Using an electrical one, that's in pararrel with the PCV, and just using it at WOT, might work.

A good air/ oil vapor, seperator is always a good idea.

If there's a mechanical problem, then it needs to be dealt with, using a vac pump to make up for leaking rings is a patch rather then a cure, IMO. Blowby, the rings, allows for excessive moisture, and acid fumes getting into the oil, and both play havic on bearing wear.

 

[Maltman]

Well, what I think I need to do first is get an accurate idea of how much pressure is being created under wot and various driving conditions. I was thinking of setting up a temporary pressure gauge off the dipstick tube and seeing what happens.

Otherwise, I agree, not much use in trying to make up for rings that are way too bad...I'm just hoping that isn't the case since it is a fresh rebuild.

I don't understand the dry sump idea too well, so I'll have to do some research....but thanks for the idea.

 

[gnxtc2]

The problem with the GN is once boost is made, the boost goes backwards into the PCV. The PCV is "suppose" to close and not allow boost into the crackcase. But that rarely happens. Some put a checkvalve (Pete Tomka) inline in the PCV vacuum line to prevent this. But you still have to rid the excess pressure inside the crackcase. Some put open breathers in the valve cover. This helps but not quite. Last option is install a LT1 electric vacuum pump and turning it on when you heart desires. (Best way IMHO).

Billy T.
gnxtc2@aol.com

 

[Maltman]

The problem with the GN is once boost is made, the boost goes backwards into the PCV. The PCV is "suppose" to close and not allow boost into the crackcase. But that rarely happens. Some put a checkvalve (Pete Tomka) inline in the PCV vacuum line to prevent this. But you still have to rid the excess pressure inside the crackcase. Some put open breathers in the valve cover. This helps but not quite. Last option is install a LT1 electric vacuum pump and turning it on when you heart desires. (Best way IMHO).

Billy T.
gnxtc2@aol.com

Yeah, I have the catchcan and checkvalve in place now with the dual breathers on the gn1 valve covers....still having problems under heavy boost.

As for the pump, I think I remember reading something about how that particular pump doesn't pull more than 2-3" of vac at best....in fact, that has been my problem with deciding whether to go with mechanical or electrical....nothing has popped up that displays a really good functioning elec. pump.

I could just have bad info and maybe that is all I need to do to make a good vac system. Again, I want something to "replace" the pcv to throttle body lines so I'm never worried or having to clean the intake again. Because of this, I've been leaning more toward a mechanical pump system.

Any current stats on those elec. pumps??

Thanks

 

[gnxtc2]

Look in a shop manual for the operating specs of a LT1 vacuum pump.

 

[TurboTR]

Well..... if you have that much blowby or whatever it sounds like you have another issue to address. Dropping the crankcase pressure won't stop the oil from accumulating upstairs. I think generally vacuum pumps are used to reduce windage and pumping losses and thus free up some hp, not as something to try and suck up excess cylinder pressure loss from bad rings, cracked block, blown hg, etc

JMO, but it seems like you are maybe engineering an elaborate patch to try and cover a far more pressing mechanical issue. Assuming of course that your crankcase is not simply pressuring up from manifold boost pressure, as was asked. Consider that most cars don't have the issue it seems you are seeing, even at 30+ psi boost. IME, something is wrong if the crankcase is pressuring up that much...

TurboTR

 

[Scott Atk]

Does anyone know if the MOROSO style vacuum pumps are rated for continuous duty?

 

[azgn]

if you use the LT-1 pump, you will have to run it all the time....otherwise, the engine won't breathe at all, and you will have all kinds of problems.....

you don't want to overdo any vacuum in the block or you'll suck oil right off the crank

bottom line, if your rings are doing their job and you have breathers on the valve covers, you should see minimal blowby

IMHO opinion. the use of a vac pump is a race only application......of the several cars using a pump here none are street cars....(and we did have a problem setting the proper vac on a belt driven pump....)

as mentioned, a vac pump shouldn't be used as a bandaid......they have been shown to improve power when properly set up, however

I have had an LT-1 pump on my car in the past and am considering putting it back on...I am not convinced those pumps will stand up to constant use on a street driven car....since my street driving is just to the track, I may give it another try...of course, it is possible to put the breathers in when not racing and not use the pump during that time

 

[Lee Thompson]

need a good plumber

If plumbed correctly, an LT-1 pump will work @ boost and still allow blowby to escape when not boosted.

 

[azgn]

uh yeah, but don't you have to have it running? How do you unseal the block with the pump attached?

 

[703crewchief]

Have any of you guys tried the old header evac kit from Moroso? Instead of putting it in the header collectors, put the check valves at a low part of the downpipe. No mechanical or electrical BS.

 

[azgn]

won't work on a turbo car....not enough velocity after the turbo......

 

[703crewchief]

I've seen it work on a turbo car. Ryan Mosley has it on his T-type. That's a nine second car! If it can evac that crankcase, its working alright. Also I've seen plenty of turbo cars making the banners on the wall flap during a dyno pull. I know all of that wind isn't coming off the rear tires. That's exhaust.

 

[azgn]

just because he has it doesn't mean it works...maybe he could come on and tell us what the vac is in his crankcase? I have no doubt it helps some....

 

[703crewchief]

Alot of Buick guys like to dismiss stuff that they have never tried. Think about this. The turbine housing is not just a restriction, its a twisted venturi with a ton of pressure behind it. When it hits that downpipe, the gas is rapidly expanding and moving fast. Thats why a bigger downpipe and free flowing exhaust makes such a difference. So, just like draining a waterbed with running water, the exhaust evac will create a significant (better than an electric smog pump) low pressure area. Crankase windage will be reduced, your rings will seal better, velvet ropes will part, and champagne will fall from the heavens.

 

[Maltman]

Well..... if you have that much blowby or whatever it sounds like you have another issue to address. Dropping the crankcase pressure won't stop the oil from accumulating upstairs.

TurboTR

Interesting question about that point too....I shine a flashlight down the return galley and it is basically a view of the block....the holes do not line up well at all!

Anyway, since I'm not sure how much pressure is being made, my thinking was that excess pressure or blowby would need to escape somewhere. That somewhere is through the return galley and some through the pushrod holes....since that galley isn't open hardly at all (mind you these are factory heads on a factory block), it wouldn't take much turbulance to create difficulty for the oil to return...hence puddling in the valve covers and leaky breathers.

Again, I'm just throwing thoughts around and have no hard evidence to stand on....but I'm not about to tear the motor down to try and grind out the holes to match.

...which makes me wonder...do aftermarket heads compensate for this factory mess? Or is it possible that I'm lucky and nobody else has this problem...or maybe they just haven't witnessed this misalignment?

 

[azgn]

All I can say is prove it with a vac gauge on the block....we have proved it with pumps