Corvette-Dan

I am looking to upgrade to a LS6 manifold on my 99 LS1. I need to retain the EGR and air pump. Will I have issues or is this a direct bolt up? I have searched but can't find exactly my circumstance. Any help would be appreciated. Thanks

Smoken1

It will bolt up. You will have problems with the coolant pipe under your LS1 intake, you need to change to the newer style with no cross over tube..
Btw there is no EGR valve on a C5

neutron82

you won't have to mess with the air pump pipes either because they bolt to the exhaust manifolds not the intake manifold... you can keep your crossover tube under the intake if you knock the ribs off the bottom of the ls6 intake, actually I prefer doing that since the 4 port crossover is better... you can use a flathead screwdriver and a hammer and the ribs will pop right off flush with the bottom and it will not decrease the structural integrity enough to worry about, I have put 16psi through mine with the ribs removed and had no problems at all

Bill Curlee

You can rearrange the STEEM CROSS OVER TUBING under the intake to make it fit properly. All you need to do is MASSAGE the vent piping downward to be closer to the engine valve valley close out cover. OR, you can install some block off plugs to the rear head steam vents and add a 2001-2004 front cross over pipe.

EVERYTHING else is a direct bolt in application. YEP, The C5 DOES NOT have an EGR valve/system. It does however have an Air Injection Reaction (A.I.R.) System that involves the EXHAUST MANIFOLDS. Not the intake manifolds. It injects fresh air into the exhaust manifolds to aid in early cold engine CAT Light off.

The main difference between the LS1 and the 2001-2004 (ZO6) manifold is the later manifolds have a larger PLENUM area for more intake air flow at higher engine RPM/loads. The larger plenum contacts the early LA1 steam cross over tubing under the manifold.

Corvette-Dan

Thanks folks. For some reason I thought the earlier LS1 had EGR and the latter did not. Thanks to all for the responses.

Bill Curlee

The F Bodys and trucks have the EGR at the front of the manifold. The C5 and C6 do not employ the EGR.

Bill

Corvette-Dan

My manifold is due today via FexEx. Still waiting for my oil pressure switch. Planning on the swap.next Friday. Will post pictures. Thanks again.

Cmanride

Gordy M

According to GM the manifold change is worth 5 hp and 25 ft-lbs of torque (6 speed--360 ft-lbs for automatic) and the torque comes in earlier with the 2001-2004 manifold:

•300 lb-ft is delivered at 1,000 rpm - 400 rpm earlier than before

•320 lb-ft is delivered at 1,400 rpm - 800 rpm earlier than before

•340 lb-ft is delivered at 2,500 rpm - an amazing 1,400 rpm earlier than before

•Maximum torque of 360 lb-ft for automatics, 375 lb-ft for manuals, arrives at 4,400 rpm.

rcastor426

I put the LS6 intake on my 99...I also changed the coolant tube, changed out the valley pan/pvc system, added 2004 243 heads and ls 6 cam. 3.15 rear gear, stock 4L60 with stock stall. 360hp/360tq at the rear wheels. Really woke up the car,