I came up with a quick and easy way to add crankcase breathers to an LT engine. The factory LT oil filler tube has a 1 ˝” OD at the top and K&N makes a clamp-on crankcase breather (PN 62-1460) with a 1 ˝” ID (a perfect fit).

You can remove the oil filler cap on the passenger and install one K&N breather. Or, install two breathers, one on each valve-cover like I did. However, that requires obtaining a used GM valve-cover (non-LT) for the driver’s side with the filler tube located towards the front. The local GM salvage yard had a box full of this style valve-cover, therefore they are very common.

Here are some photos.

 

Sorry for the dumb question, but whats the point of this?

BTW the motor looks clean, I like it

 

Why do you still have the PCV hooked up with the breathers?

 

The closed PCV system is a much better way to keep your engine crankcase purged of harmful gases.

 

With large CI engines turning high RPM, crankcase pressure is significantly increased along with some blow-by. Race engines often use vacuum pumps to pull-down the crankcase pressure, while other race engines use scavenger tubes to the header collectors to pull-down the crankcase pressure. The breathers like I have installed are a very conservative approach to reducing crankcase pressure. Basically, my car is a street legal bracket race car and I was getting some oil blow-by from the crankcase pressure.

Yes, I left the PCV valve in-place.

WD

 

I agree with you on strictly street car engines, however, my application is a different situation.

WD

 

So you only did this for cost concerns over going to vacuum pump or scavenger tubes?

 

Ok thanks for clearing that up for me.

 

Indeed, unless you want the car to suck in oil like crazy.

 

Only 381ci, only turning 7,000rpm, and only running 800HP/800 lb-ft on nitrous, but the stock PCV system works just fine on my engine.

 

I also left the PCV valve and tube functional along with the addition of the two breathers. I was getting some oil traveling back up the fresh-air inlet tube on the passenger's valve-cover back into the throttle body. Whereas, the fresh air flow should be through the throttle body back to the driver’s side valve cover air inlet.

With my crankcase breather configuration and the PCV still functional (and at lower RPMs), I would expect fresh air is now drawn-in “primarily” through both valve cover breathers. However, at high RPMs if the crankcase pressure “exceeds” the volume of the PCV system, crankcase pressure would then be released (back-flowed) through the two breathers.

Additionally, I’ve never liked the LT’s OEM, PCV valve location (intake manifold center) which leaves the driver’s side valve cover somewhat neutral in crankcase ventilation (I know the push-rod passageways provide some flow, but possibly not enough). For example; most GM V8 engines have the fresh air inlet on one valve cover and the PCV valve on the other valve cover. Consequently, that design completely ensures positive PCV flow on both banks of the engine, whereas the LT configuration does not.

And as I pointed out previously, most “all out” race engines have vacuum pumps, scavenger tubes, or multiple crankcase breathers. So, I don’t think I could be completely wrong on my theory here with the two breathers.

WD

 

I run scavenge tubes...along with the pcv

I was just told to do it this way...never asked any ??? on it

 

I am gonna run straight breathers with no pcv and no evac,but will put a pcv with a seperator on it if moisture becomes a problem. May put an electric vacuum pump on it at some time in the future.

Pcv on high compression engines could suck oil down in the cylinders causing a detonation problem, you don't want that.


David

 

So the inside of your intake manifold is bone dry, not a sign of oil anywhere?

 

My car had 120K miles on it when I took out a rod bearing, but my intake was caked up with oil. Took me about 20 minutes at the car wash and 2 cans of degreaser to get that crap out of there.

Will running a breather setup like the OP help the situation? Or what should be done to stop oil from getting inside the intake? I have heard to add an water/oil seperator like on an air compressor inbetween the PCV and intake, would that solve it? My mods are in my sig, but the motor isn't together yet.

Sorry for the thread jack, and I'm not trying to start anything. Just trying to solve the problem