cdee63

I am gathering parts for my LS6 intake install/updated valley plate PCV/replace knock sensor day soon. From what I understand the 4 corner factory steam pipes will not allow the manifold to sit as it should. What are some other options that some have done besides blocking the rear ones, for me that is not an option.

Fast one

How did the factory connect all four or didn't they? I bought a 4AN hose kit to connect all four corners to clear a FAST intake manifold but it was difficult to install and didn't fit well, it would've fit a pickup truck better with the extra hood and firewall room. The 4AN hose is also large and stiff. The kit was removed and the rear vents were blocked again as they were for the past 12+ years. There are various steam vent kits at Summit, Jegs, etc, here's the one I bought, note how good the fit is with the engine not in a C5:

71 Vert LS1

I'm running a LS6 in my 98 Wrangler. LS6 intake. LS1 valley cover with the PVC in the left valve cover. Stock four corner steam plumbing. Where is the issue with the LS6 PCV?
Having said that I've done a few LS swaps that only used the two front steam ports. Zero issues.

contraption22

In the rear, I used the front steam crossover from a truck. I believe it was an LQ4 6.0. In the front, I used an LS6 front crossover. I tee'd them together with hose and then into the radiator nipple.

93Polo

There is the truck solution:

Bill Curlee and I have run the Corvette front crossover in the rear and tee'd it in. I ran the hose over to the heat hoses on the passenger side and tee'd at the port on the top of the radiator. It does get cramped at the firewall.

https://www.corvetteforum.com/forums...fications.html

93Polo

Believe that is motion race works, and my bracket did not work with the factory fuel rails.

JHrinsin

I used the GM Vortec truck rear cross over steam tube #12605716 (now replaced by #12694768) with the Dorman #56390 early style cross over steam tube seals (4-pack) GM #12551933. Along with a 1/4" x 1/4" x 5/16" brass Y-fitting from eBay, some 1/4" & 5/16" coolant / fuel injection clamps and 1/4" coolant rated hose that runs along the driver side fuel injector rail . You may have to very carefully massage the shape of the coolant tube only after installation for a small amount of extra clearance around the oil pressure sensor or remote adapter fitting as well as which ever intake manifold you may be using. The hose running to the front looks excessive in the photo, but after installing the LS2 throttle body and adjusting the hose routing it wasn't too long.

cdee63

^^ Thank you! This is exactly what I was looking for. I already have four ICT steam port fittings threaded with 1/8 NPT. A few barbs, a Y fitting as you have, some hose and I'll be all set. I also plan on a CC as you also have.

Markolc1981

Thanks! I was getting ready to order block off ports for my FAST intake install, but the truck crossover tube seems like a way better idea.

Kubs

I too used a truck front crossover on the back and just ran the tubing up to a y fitting in the front. They are dirt cheap used.

grinder11

I ran the factory 4 point under an LS6 intake for 35,000 miles with no issues. Then ran it under a FAST 90 for 30,000 more. Might be a little interference, but nothing to worry about....

cdee63

^^ Did you have to do any material removal from the bottom of the intake?

schmuckingham

I use the Motion kit on my FAST 92.

grinder11

I did not. I did countersink the valley cover bolt holes to use flat head screws, but that was it....

Markolc1981

And the 4 point early LS steam lines fit underneath the FAST intake just fine? That's fascinating. Didn't have to rubber mallet the lines flat or anything?

I'd rather not buy parts that I do not need, I was set to buy new crossover tubes and fab something up.

Would it work with the low profile FAST bolts for the valley cover?

grinder11

I did this almost 20 years ago, so I can't remember everything. But I do know for sure I didn't have to flatten the steam lines (still have them), and I don't recommend doing that. Because you could over flatten them, pinching them shut, and then there's no steam flow. Which defeats the whole purpose. I may have used a Dremel or die grinder to help clearance the intakes, but can't remenber for sure. If I had to guess, Id say I did no clearancing to the intakes. I do know that I bolted them on without either manifold cracking, having any vacuum leaks, or bolts not lining up. And they worked well for 10s of thousands of miles.......

Markolc1981

I've been deep diving this for several days now, and it looks like if you're using an LS6 valley cover, then there's really just no way to use the LS1 steam lines with an LS6 manifold or FAST. The reason is the LS6 valley cover has raised bumps (for the bolts on the underside of the valley cover to hold he PCV system in place) and those bumps line up nearly exactly where the LS1 steam lines run. Those bumps are tall enough to match the height of the lower profile FAST intake manifold bolts. I just don't see a way even if you wanted to bend the lines to make it happen. Maybe if you installed it backwards and have the coolant exit towards the firewall, then run a line all the way back to the radiator it might work. I will play with this once I'm knee deep in my valley cover install later this Spring.

Looks like the option JHrinson posted above is the best method.

cdee63

I was talking to a friend about this a week ago, he has a Vega with an LS3 stuffed in it. Had a set of 4 ICT billet steam ports threaded for 1/8 NPT laying around he sent to me. I picked up 4 brass fittings, a tee, one of those 1/4, 1/4, 5/16 Y fittings and some appropriate hose. I am expecting my knock sensors and LS6 valley cover today, I will tear into it this weekend. Thanks for all the suggestions!

99FRC Newb

Looking forward to your experience this weekend! I’m pulling my intake off shortly and have been considering the 4 corner kits.

Rx7Rob

I'm using LS6 intake on LS1 with original tubes.

Snap the ribs off the bottom of the intake and massage the tubes SLIGHTLY with hammer. Think I only had to do it in a couple of places. Fits w/o issue (did this back in 2012 on a cammed car that primarily is for HPDEs).