Help with LS3 connections and PCV

[derotoreut]

I'm still working on my LS3 swap and I'm trying to understand what is the correct way to connect the valve cover fittings and other ports on my engine. I am overwhelmed by trying to read and understand discussions about PCV systems, catch cans, etc.

I have attached a couple of pictures of my engine and circled the areas I have questions about. From trying to search online, it seems that everyone has opinions on how these Gen IV engines are supposed to be set up. If anyone can offer any assistance it would greatly be appreciated.

By the way... my engine is a GM connect and cruise that I bought quite a while ago (without ECM). It's a 6.2L Gen IV, 376/480HP. I am running Holley Terminator X Max with Dakota Digital's BIM-01-2-HLLY: Holley EFI Interface Module for Holley Terminator X Max.

Also, my engine has a flexible tube that appears to run from the valley cover to the TB. Do I keep that as is?

What is this used for? And do I need it?


How do I connect pass side PCV fitting?


What about these connections?

[litebulblsc]

Back side of the left valve cover is plugged, leave it plugged.

Same pic, the red cap is your vacuum source for power brakes. Either hook it up to a vacuum brake booster or leave it plugged.

Valley cover to throttle body is your actual dirty side pcv. This is where you install a catch can.

Right side valve cover front fitting is for fresh air into motor. Usually hooks up to air intake pipe so it is filtered and metered by the maf. If you run Holley (maf-less) you just need filtered air in (don't want to be sucking in dirt)

Other apparatus is a purge solenoid for gas tank evap system.

[87chevy.com]

why cap off the driver side rear.. do you not want it to vent equally like the passenger side? why not just tie it into the passenger side that will go to the fresh air in take (or after market catch can?) set it up like factory, run it..... tune it, mod it, and then tune it and go from there... if you do a bunch of stuff at once if you should run into a problem, you might be grasping for straws for help as theirs no reference when it ran good...

[derotoreut]

Originally Posted by 87chevy.com

why cap off the driver side rear.. do you not want it to vent equally like the passenger side? why not just tie it into the passenger side that will go to the fresh air in take (or after market catch can?) set it up like factory, run it..... tune it, mod it, and then tune it and go from there... if you do a bunch of stuff at once if you should run into a problem, you might be grasping for straws for help as theirs no reference when it ran good...

Thanks for your input and help. I'm not sure I understand your routing suggestion. I know you say to set it up like factory, but I don't know how to do that with my bare engine. It was never set up that way. This engine has never been run, so I'll have no reference.

[derotoreut]

So this is kind of what I was afraid of, but expecting. There are going to be differing opinions on how to set this up. I was hoping there was a straightforward way of doing this on a LS3 that everyone had a general consensus on (wishful thinking). Hopefully, more folks will chime in and give some advice.

[litebulblsc]

I gave you the factory information. I own 1 factory LS3 car, and installed one in another car.

The left side valve cover is capped from the factory.

[derotoreut]

Litebulb, this drawing appears to show the set up you are referring to:

[litebulblsc]

Yes, I agree with the picture for a "stock" engine.
That is how a factory LS3 is done, except in the picture they added a simple catch can on the dirty side.

[87chevy.com]

Originally Posted by litebulblsc

I gave you the factory information. I own 1 factory LS3 car, and installed one in another car.

The left side valve cover is capped from the factory.

strange GM oddity ..
clint

[LS short box]

So here's what I've done on my L92's dressed as an LS3. Using a LS3 Corvette intake, valley cover with PCV and throttle body. Look's just like your LS3.
Nipple on the left valve cover is capped off.
In the pic on of the first post of the throttle body and intake. I cut of the nipple off and drill and tap the hole plugging it. Not needed on my swaps.
Pic of the back of the intake the capped nipple is for power brake brake booster if needed.
Then I connect the intake nipple on the right side of the intake (right behind the throttle body) to the nipple on the valley cover that contains the PCV assembly on the under side of the valley cover.
On the right side valve cover the fresh air tube I connect it to the air intake after the mass air flow sensor. Piece of cake. LOL!

[derotoreut]

Originally Posted by LS short box

So here's what I've done on my L92's dressed as an LS3. Using a LS3 Corvette intake, valley cover with PCV and throttle body. Look's just like your LS3.
Nipple on the left valve cover is capped off.
In the pic on of the first post of the throttle body and intake. I cut of the nipple off and drill and tap the hole plugging it. Not needed on my swaps.
Pic of the back of the intake the capped nipple is for power brake brake booster if needed.
Then I connect the intake nipple on the right side of the intake (right behind the throttle body) to the nipple on the valley cover that contains the PCV assembly on the under side of the valley cover.
On the right side valve cover the fresh air tube I connect it to the air intake after the mass air flow sensor. Piece of cake. LOL!

Sorry but I'm somewhat confused. Do you have any pictures?
So you're not running any type of air/oil separator?
Is your set up like the diagram except no catch can? If so that's what I have right now once I eliminate the purge solenoid and connect the pass side valve cover to the TB air intake pipe.
No MAF because I'm running Holley Terminator X Max.

I currently have the tube that runs from the valley port to the TB.

[LS short box]

Per your pic above the red cap is the nipple I cut off flush with the throttle body and drill and tap for a plug basically for better looks.
Per your pic you have the "stock" u-shaped tube that runs from the LS3 intake to the LS3 valley cover that has the PCV assembly on the under side of the valley plate. That PVC assembly is the oil air separator as far as I know. Early LS1 engines had a PCV valve in the left valve cover and tended to suck oil into the intake. See pic of my LS6 with an aftermarket catch can.
I'm running a LS3 mass air flow sensor and all GM for engine/trans control. As I understand Holley is speed density so no mass air.
So the question is do you need to run a fresh air source to the engine from the tube on the right side of the valve cover to the intake tube. Honestly I don't know but I would say you have to have some source for engine fresh air.
I've seen pics of a small cone type air filter clamped to the tube.
I haven't done it that way. I run a 3//8" rubber hose from the tube to the air intake tube after the mass air.

[derotoreut]

Thanks for the clarification. I think I would either configure it like the sketch in post #7. Or I'll add a tube to the driver side valve cover and tee it into the pass side valve cover and tie both into my air intake before the TB.