Intake Manifold Swap

E-mail jmX with corrections

Lets begin:

(Note,f-body specific instructions will be orange, and C5 specific instructions will be yellow.)

First step is to remove the air intake/maf assembly. If you have an F-body, just loosen the screw on the intake tubing going to the throttle body, unclip the lid, and pull it all off in one piece. If you have a C5, unscrew the airbridge where it connects to the throttlebody, then unscrew the clamp where your maf goes into your air filter assembly...remove the whole tube/maf piece and set it aside. Next, disconnect the sensor plugs off the throttle body, pull off the coolant lines going to the bottom of the throttle body, disconnect the throttle cable and pull off the cruise control cable if you have it, corvettes will have no throttle cables as they are fly by wire.

Unbolt the EGR pipe from the top front of the intake manifold. Then, if your new intake manifold doesn't have EGR provisions, remove the wiring harness going to the egr assembly. You need to unbolt the egr tube from the passenger side header (2 10mm bolts), and then unbolt the 2 15mm bolts holding the EGR assembly to the passenger side head. Remove the assembly and set aside. You will need to put a block off plate on your headers if you are removing the EGR assembly. Do this now.

Disconnect each wire harness going to the 8 injectors. To do this, push upwards on the shiny metal clip on the bottom of the harness, then pull of harness off the injector. There was also a wire harness on the drivers side fuel rail going to a valve of some sort, I disconnected this as well.

Remove the big vacuum hose from the brake booster. The picture on the left shows which hose this is. Now remove the remaining hoses/connectors going to the front of the intake manifold. There is a hose on the left, and a plastic connector for fuel on the right. To disconnect the plastic connector, you need to press in the grey ring and then pull the whole connection off the brass fitting on the intake manifold. Unbolt all 10 8mm bolts that hold down the intake manifold to the engine. These are the 10 bolts that DON'T have threads on both ends. You should be able to totally pull out the first 6 bolts, but just leave the back 4 sitting in the hole after you've unbolted them as they'll probably hit the cowl. On the corvette you only need to leave the back 2 in.

Now, holding the back 4 (or 2 on the C5) bolts up out of their holes as far as you can try to slide the intake manifold out towards you as far as you can without pulling too hard, as there is still a hose attached to the back! Now, reach behind the intake manifold and there will be a sensor and a small vacuum hose to disconnect. Pull both of these off. Leave the big vacuum hose connected for now, the other end was disconnected in the previous step.

Now you can pull the intake manifold out a little more into the open since its just connected by the fuel line now. We are going to leave this connected.

Remove the 4 remaining bolts holding the fuel rail to the intake manifold. Now, with one hand hold the intake manifold firmly, and with the other pull up on one side of the fuel rail (pull by grabbing the rail, not the injectors). The 4 injectors on that side will "pop" out of the hole. You can also try pulling up the front of the rail to pop out the front 2 injectors on one side first, then pull on the back end of the rail for the back 2 injectors...then do the same for other side.

Here is the fuel rail totally disconnected from the intake manifold. Be carefull with it and set it aside somewhere in the engine bay for now.

Now that the old intake manifold is off, you can compare it to the new intake manifold. The floor of the manifolds differ as you can see in the picture.

The next step is to remove the old coolant lines that run between the heads. There are 4 bolts holding it down at each end of the "X" shaped pipe. Be carefull with the bolts, you don't want them falling into the intake ports of your heads. The front passenger side will be held down with a double ended bolt...the PVC rubber hose has a grounding strap going to it which is held on by a nut. This nut is secured to the hose so you dont need to worry about it falling in the intake ports. There are also 2 green plastic clips that hold the knock sensor wires to the old coolant pipe. These clips need to be totally removed since they wont fit under the new manifold. Peel off the tape holding them to the wire and they'll come right off.

Due to parts availability, I chose to use 2 front intake pipes off a 2001 car, rather than 1 pipe and 2 plugs. You can see in the picture how the new pipes are to be oriented relative to the old pipe.

Since I needed to run 2 *FRONT* coolant pipes it meant I needed to block off the unnecessary rubber line that I'd have on the back pipe. To do this, I found a perfectly sized bolt that only had threads half way up, covered it in Ultra Copper RTV sealant and plugged it in the back of the hose. The picture to the left shows the bolt half way out before we coated it with gasket sealant. Once the bolt was totally inserted in the hole, I used 2 hose clamps to tighten it down. This bolt is NOT coming out :)

Here you can see the 2 pipes are now installed, with the plugged one going on the back and the unplugged one up front (this is the hose that normally runs to the throttle body, unless you have the TB Bypass mod)

From this point on, its all the reverse of the previous steps. Firmly press all the injectors back into the intake manifold, one side at a time. Make sure they are in GOOD, then put the 4 bolts in that hold the rail down (making sure the metal brackets went on like they came off). Next, re-insert the 4 rear long intake manifold bolts back into the manifold (remember, the drivers side rear of the manifold has a metal bracket that is held in place by the rear 2 bolts on that side) and while holding them up, slide the manifold back into place. Reconnect the rear sensor, as well as the small vacuum line, and snake the big brake booster line back into place and reconnect it. Once everything in the back is reconnected, slide the manifold into place until those rear 4 bolts are perfectly lined up. MAKE SURE you don't catch any small vacuum lines underneath the intake manifold before you bolt it down. I forgot to check on one install and the pinched vacuum line left me without A/C controls. Having to go back in and replace vacuum line because of a stupid mistake sucks. Now, hand thread in all 10 of the bolts now.

Once all 10 intake manifold bolts are hand threaded as far as they'll go, tighten them down with a wrench and then torque in the order shown in the picture on the left. You need to torque these down in a 2-pass fashion..the first pass, tighten to 44 INCH-lbs, then, on the 2nd pass torque them to 89 INCH-lbs. Again, note those specs are in INCH lbs. If you don't have an inch pounds torque wrench, just tigthen the bolts hand tight...its only about 7 ftlbs of torque on that final pass and the intake seals with rubber gaskets so its doesn't need much pressure at all to seal. Reconnect the throttle cable bracket and tighten the 2 bolts to 89inch pounds. Now, the PVC line has a grounding strap that attaches to the front passenger side coolant pipe bolt stud...reconnect this.

The very next day after the install I took the car to the dyno. The results were astounding! I gained a peak of 24rwhp, 14ftlbs of torque. The dyno graph on the left shows the results.