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LT4 valve cover using 2 passenger side covers question

4K views 8 replies 4 participants last post by  Marky Dissod 
#1 ·
Recently came into possession of 2 passenger side LT4 valve covers. Now my question is I know the 2nd will fit the drivers side by installing flipped around and I have a 2nd oil fill cap but I'm wondering what's best to do with the unused ventilation hole...
Should I just cap it off with a small section of hose with a plug in it, find a breather that would fit there, or maybe even tee it into the other cover's hose that connects into the throttle body?
In either case any recommendations as to what to use to cap it off, tee into the other hose, or what breather to use would be appreciated!
 
#2 ·
Recently came into ... 2 passenger side LT4 valve covers...I'm wondering what's best to do with the unused ventilation hole...
Should I just cap it off with a small section of hose with a plug in it

Or just a plug. that's what most, myself included, do.

find a breather that would fit there
An open breather isn't a great option for a couple reasons. The air in the system is metered by the MAF. Introducing unmetered air in tells the PCM along the way that there is more air and the inevitable result is it dumps more fuel to compensate. Also, the PCV system holds a vacuum. Introducing an open breather decreases this vacuum pressure and prevents the PCV system from flowing at peak efficiency and can, in an extreme case, also lead to inadequate PCV gas removal.

or maybe even tee it into the other cover's hose that connects into the throttle body?
I've messed w/ this idea, but those systems are designed for (primarily) corvette intake manifolds which have the PCV outlet adjacent to the PCV inlet on the driver's side of the intake. On our systems, the PCV outlet is in front of the intake. If you could find a way of plumbing it w/ a tee to maintain proper directional flow AND retaining the same vacuum pressure, you'd be onto something. You can't really emulate the same corvette system w/ a tee since the pass side on the corvette hasn't the same pass side provision that we have. Ours is on the pass side. Theirs is on the driver's side. One would think then that using both would require plumbing from the TB to both valve covers while halving the amount of vacuum to both. You would then also be presented w/ the issue of blow back from 2, instead of 1 orifices.

I said 'nah'. The stock system is fine. I'm just plugging the driver's side hole.
 
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#4 · (Edited)
Fraid I don't get it?
The setup would be exactly the same. The tee would be attached to the provided or alternate PCV valve...

FWIW, I use the Gen3 SBC fixed orifice PCV fitting, instead of the previous PCV valve.
You mean this?


Yeah. Me too.

...the only addition being a hose running from the tee (smaller diameter side) and check valve to the driver's side VC provision.

Right now, every six months I just switch which valvecover is connected to the throttle body.
Now I'm the one who doesn't get it. 'Why?' springs immediately to mind. Just curious as the intent is not to challenge, but rather to learn.

It'd be simpler to permanently connect BOTH simultaneously, but different size hoses would probably be necessary, to maintain the proper vacuum/pressure relationship.


Agreed, but I don't know how you could effectively, and w/out looking like total ass, tie the lines together over or around the intake. Best would be to hard plumb something to the front, under the TB and then around.
 
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#6 ·
Alternate PCV valve? I only have the fixed orifice PCV fitting between the crankcase vent [under the TB] and the side of the intake manifold.
Yeah. That could be considered an alternate to the one pictured. Unless you're saying you've a newer LSx intake w/ an integrated fixed orifice PCV valve. I've been running the above valve w/ my B/D-LT1 setup for years w/ a spotless clean TB every time I check it.

Part of my confusion may be that I only know the PCV routes of the B-LT1, and am inferring that the F-LT1 & Y-LT1 are the same.

Are they different?
well, depends. Simple answer is yes when it comes to LTx engines in that they've the opposite side issues we have when it comes to PCV, alternator and hence, valve cover options (the stupid alternator/VC notch issue). The more robust answer is that you have to know what year a) valve cover, b) platform and c) PCV provision you're using. Many, myself included, run centerbolt VC's that are pre-LTx, but which still ran and required PCV provisioning. So there's a few variables to consider. Fwiw, I know of no years or platforms that ran a dual VC PCV setup like we're discussing. It's just ****s and grins to me unless I can see concrete proof that a dual setup would actually scavenge more toxicity out of the crankcase than the stock setup. Until then, I'm just plugging the hole :)


What are you all using to plug it?
Once upon a time I did run an open breather. When I went back to closed, i discovered that if I filled the base of the breather w/ RTV and made sure it was solid and wouldn't budge, it made a great plug. that's my story and I'm sticking to it.
 
#5 ·
I believe the y-body system is the only one that's different then the other lt1 setups and what I was hinting at. But sounds like just plugging the drivers side is easiest. I mentioned a piece of hose and that being plugged as I wasn't sure if anyone had found something to securely plug the hole directly. What are you all using to plug it?

Also could always tee both sides together to a valve before the throttle body and then use the valve to alternate sides and not have to remove and reattach hoses each time.
 
#7 ·
I ran one side in the stock manner and the other side just an open breather. I had a slight split BLM issue and the tuner asked what my configuration was. I told him and he recommended I either combine them or close the one up. I combined them with a T and my split BLM issues dissapeared.
 
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