Bill Curlee

Ive done a LOT of work on Early C5s and Late Model C5s. Sometimes the Steam Piping below the intake manifold needs to be modified. Ive posted information on this topic several times but never did a dedicated POST on the details.

SO,,, Here are some pictures and details on all the things that you can do with the steam piping to make different intake manifolds fit and to ADD steam cross over piping on late model C5s that did not come with rear cross over piping:

Below is a picture of 97-2000 C5 LS1 steam crossover piping. This piping fits nicely under the early LS1 intake manifold as it is from the factory:

The piping connects ALL FOUR corners of the cooling passages in the head and allows the air/steam to exit at the front drivers side of the pipe:



If you want to install a LS6 or 2001+ intake manifold (same manifold) the common steam piping in the center can and will contact the bottom of the late model intake manifold because that part of the intake is deeper than the LS1 manifold and prevent it from sealing on the intake ports.

Some things that you can do to resolve the problems with the piping. DO I have to remove the piping?? NO You don't!

The fasteners that secure the valve valley cover to the block are TALL. You can GENTLY massage the piping down with a rubber mallet and a wood block so that it sits BELOW the tops of those bolts. Once you do that, the LS6/2001+ manifold should fit without any issues. Make sure that the Knock Sensor wiring does not get pinched or damaged. You can also remove some of the ribbing on the bottom of the intake for a tiny bit more clearance. I used a electric hand held grinder with a grinder wheel and just lightly evaporated the ribs o the manifold below:





Intake Manifold Gaskets. Over time the manifold gaskets get compressed and hard and no longer properly seal the head/intake port. Its recommended that you install a new set of O Ring gaskets for best sealing. They are reusable IF they are in good shape and have proper standout above the sealing surface:





This is what is inside the Knock sensor wells. The black rubber cap keeps the well sealed but it is NOT water proof. If you wash the engine, you can flood out those wells and destroy the Knock Sensor. Use a little Blue RTV and seal the cap.



If you have a 2001+ LS engine, you will NOT have the piping under the manifold. The rear steam vents will be deleted by the use of Block Off caps. You will Only have a single cross over pipe at the front of the heads.

I have done extensive mods to my 02 LS6 and having steam vents at the rear of the heads is desireable. To regain the rear steam vents, I could not just ADD the old LS1 piping. I have a FAST 90 intake manifold and the bottom of that manifold is even closer to the valley cover. In fact, if you install a FAST intake you must remove the OEM valley cover fasteners and install LOW PROFILE bolts.

To regain the rear piping, I purchased a new 2001+ front steam cross over pipe, reversed it 180 degrees and installed it on the rear vents. I connected the vent line to a rubber hose and used a METAL "T" to plumb the line into the front line.:



NOTE!!! I needed to lightly bend the piping to clear the rear of the intake manifold. I always set the intake manifold on the heads to see if it sits FLAT on the heads. If it rocks around and doesn't sit FLAT, its hitting something:



Bottom of an unmolested ZO6/2001+ Intake Manifold:




Bottom of an unmolested 1997-2000 Intake Manifold:



Here is a close up of a 2001 with steam block off plugs and the TALL Valve valley bolts, stock vacuum line:





Back of the intake manifold where the little vacuum line connects to the MAP Sensor:



SO,,,, I hope this helps clear up the under the manifold steam cross over piping and some intake manifold information.

Bill

CamminC5

Thanks Bill. As always, your level of detail is 2nd to none.

Bill Curlee

WOW! That was a quick reply! LOL!!

CamminC5

I always look at your threads. They all have great info.

Pounder

Bill do the later years have the coolant lines running through the Throttle Body, if yes what did you do with that ???? (just more info as long as your doing the steam pipe conversion)

Bill Curlee

ALL C5s have coolant that runs through the lower portion of the throttle body. The under the manifold piping connects to one of the TB coolant tubes with a rubber hose and the other fitting on the TB connects to a rubber hose that ties back into the radiator.

If you want to get rid of the coolant in the TB, all you do is pop the rubber hoses off the TB and connect then together with a BRASS barb fitting and some small hose clamps.

The C6 does NOT have any coolant running through the TB Here is a couple picture of a C6 TB and a C5 TB:

NOTE! The C5 uses THREE Mounting bolts and the C6 uses FOUR fasteners to mount on the manifold. You can see the coolant piping on the C5 TB








BC

Bill

Pounder

when I did mine with the line/hose kit I ran the hose from the drivers side rear to the pass. side rear then to the front pass with a tee, ran the other hose from drivers side front over the throttle body to the tee then to the radiator !!!