crankcase vacuum pumps

toomanymodz

toomanymodz

Well-Known Member
Joined
Oct 14, 2009
I conducted a leakdown test on my new engine and all cylinders are at 9%, except for one at 4% and one at 15%. When the boost is over 15psi the pressure builds and causes my turbo to leak (due to pressure prohibiting outflow of oil from drain), thus smoking out the exhaust.

Instead of pulling the motor, are there techniques that have been tried such as large diameter or high-flow breathers, or vacuum pumps etc. I see many of the LS folks running the pumps and I'm sure it would help my 'pressure' situation.
 
Cant give you much on the details as it's just getting done to my car. nick micale is installing a electric unit on my car to help under boost. You might give him a call to discuss. Pics of how the valve covers are hoses and canister for cool pic help

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An electric unit sounds interesting. I've seen the belt-driven units but haven't seen an electric version. I'll give him a call about this. Thanks for the info and pics. BTW your engine looks fantastic.
 
There's a thread on here where an LT1 air pump is used with a Hobbs switch to engage under boost and be used as a vacuum pump to help with blowby.... Racetronix actually makes a harness for this pump which includes the Hobbs switch. I'm on my phone right now but I know I have it bookmarked on my computer. It's a great read with part numbers.
Hth
Aaron


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My valve cover breathers only have a 1/2 inch inner diameter hole. I'm wondering if simply switching to a different breather with a larger i.d. would fix my deal. Only 1/2 inch seems small to me.
 
Having this problem in the past made me look at the real problem and how to solve it on the cheap because I can make [fab] up most of the the things I need from existing parts out there or make them from scratch.

On NA motors I find that blow by can be controlled much easier than on a turbo motor especially when the boost starts moving higher. I looked at the systems out there that were available and thought that the best way to eliminate the blow by was to get it out of the crankcase before it had to travel up to the top of the motor through the V/C breathers.

Being that the problem is a percentage of the boost getting by the rings and pressurizing the crankcase which causes problems like oil leaks at the front/rear main seal and pan gasket I wanted to evacuate it at the source and add the ability to remove more pressure by allowing another escape route.

What I did as an experiment was to take a spare oil pan and drill a 5/8' hole in the pan and weld a bung on. I then ran a hose up to the engine compartment with a breather on it next to the M/C. I monitored it to see how much oil was going to blow out and cover the engine bay. I was already planning on making a catch can to return the oil back to the motor but wanted to see how it would work with out one first.

It turned out that no oil was making it out of the system probably due to the height of the breather location which was above the motor allowing any oil in the hose to drain back through gravity so I didn't even need to add a catch can.

I also have breathers mounted on V/C like everybody else and figure that the additional one from the pan is enough to keep the crankcase from pressurizing and solved my problem.

I know there are more expensive and cooler ways of fixing the problem but I did it for less than thirty bucks and a couple hours of my time.

I'm just sharing what worked for me as I like to do things the hot rodding way and not buy expensive solutions unless that is my only choice.
 
Thank you robzombie. Very informative and it just goes to say that crankcase ventilation on these cars must be considered and addressed properly, otherwise smoking and leaking will occur. I plan on replacing the 1/2 inch breathers with 1" K&N breathers. If there remains a pressure problem, I can do a mod like you did.

As far as vacuum pumps go, I'm unsure of their longevity on a street application. Of course the electric version could be rigged to a hobbs switch and i'm sure that would work fine. I'm looking for the inexpensive solution first. Thanks for the input. :)
 
toomanymodz said:
Thank you robzombie. Very informative and it just goes to say that crankcase ventilation on these cars must be considered and addressed properly, otherwise smoking and leaking will occur. I plan on replacing the 1/2 inch breathers with 1" K&N breathers. If there remains a pressure problem, I can do a mod like you did.

As far as vacuum pumps go, I'm unsure of their longevity on a street application. Of course the electric version could be rigged to a hobbs switch and i'm sure that would work fine. I'm looking for the inexpensive solution first. Thanks for the input. :)
Click to expand...


Your welcome, and I agree with the longevity of vac pumps but also the expense and just another thing to clutter up the engine compartment. I agree with the leaking oil problems also.

I never had problems with rear seals until I got in to positive pressure turbo applications. Engine condition [rings] and amount of boost dictates the amount of pressure the crankcase sees.

I love the no moving parts of my system and breathers are cheap.
 
toomanymodz said:
I conducted a leakdown test on my new engine and all cylinders are at 9%, except for one at 4% and one at 15%. When the boost is over 15psi the pressure builds and causes my turbo to leak (due to pressure prohibiting outflow of oil from drain), thus smoking out the exhaust.

Instead of pulling the motor, are there techniques that have been tried such as large diameter or high-flow breathers, or vacuum pumps etc. I see many of the LS folks running the pumps and I'm sure it would help my 'pressure' situation.
Click to expand...

Vent the front cover. Works great!
 
what a great idea! does it work for you? I have mine apart and will weld a bung right away. thanks for posting it.
 
Works great. Also install some sort of inline baffle. I'll post a picture of mine later.
 
I run a electric pump from a earlier model Corvette. I have Moroso sealed breathers on my valve covers that are both rooted under the intake to a T fitting, from the T fitting it is routed to my vacuum pump underneath the car on the driver side close to the headlight. The system doesn't pull enough vacuum to warrant a catch can before the pump, but it works well enough to vent any extra crankcase pressure. I used to have a catch can under the hood with this system, but it didn't grab a dime of oil, so I got rid of the catch can and routed it directly to the pump. Which to me is x1000 times better, because I can't stand the smell of oil vapors coming from the K&N on the catch can into the interior of the car. The line coming off of my electric pump has a line which is routed into my frame and atmosphered there.

The link below shows the pumps you can use with the wiring harness Racetronix makes for the system. The rest is just a set of sealed breathers and a trip to Home Depot for rubber lines and a plastic T.
http://www.racetronix.biz/customkititems.asp?kc=CEPH

 
You should try removing that rubber baffle as it is a restriction.

If you get oil spray or residue through the filter you could put it back on and maybe cut half of the restriction out.

You should be fine without it in there as it is high enough and in the front cover away from any major oil supply.
 
Yup thought that and tired long time ago. Didn't work all that well. While in boost the oil builds in the "goose neck" and starts to mist...baffle required.
 
Last edited:
Which compressor did you use? Pictures of the setup? Or are you just promoting that website with the same name as you??
 
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