No announcement yet.

96/97 3.4 DDOHC Intake Manifold Swap for 91-95 Engines


  • 96/97 3.4 DDOHC Intake Manifold Swap for 91-95 Engines

    Pictures can befound here * Need to find this album *

    Having just completed this swap myself and being MORE than impressed with the results, I felt the need to write up how to properly do this swap so everyone else can do it easily:

    First off, here are the major components you will need from your donor motor:

    Upper Intake (Plenum)
    Lower Intake and fuel rail
    ’96 Rear Cam Carrier Cover (Valve Cover)
    Intake pipe
    Throttle Body (Stock or whatever, but I recommend you start with a stocker)
    ’96 Plenum bolts (Trust me, they are different, Upper AND Lower)
    Plenum to intake pipe support bracket
    EGR Valve or blocker plate if Ben turned your EGR valve off
    Exhaust manifold to EGR pipe
    ’96 Throttle Cables (This is debatable, ‘92 will work with some modding, but the cruise cable will NOT
    ’96 Coolant pipe that runs from the water pump junction across the front of the motor to the lower intake. A new O-ring for that can be gotten at any auto parts store, I used a ½” I.D. ¾” O.D. O-ring, it goes on really difficult, but will seal awesome.

    You’re also going to need new gaskets and vacuum lines. I have included descriptions and part numbers here:

    12538693 - ’96 Intake gasket kit. Go to the dealer for this one. Every parts store I went to wanted $95 and they did not have it in stock. My local dealer had it in stock and I purchased it for around $30.

    24505533 - Crankcase valley to PCV Valve Line. This is a metal line with rubber elbows, and it is not cheap. If you had a complete donor motor, get the one off of there if you can, otherwise it will cost you around $45 at the dealer, cheaper on GMPartsDirect, of course.

    24505440 - Valve Cover to Intake Pipe Hose. This is a cheap one. Just get it new from the dealer.

    24505273 - Canister purge sensor to Intake Pipe/Canister Purge Vent to Intake Pipe Combo. I think $6.00, not too bad.

    10283991 - Brake Booster Hose. This one is radically different, twice as long with a lot of new bends, and it connects to the top of the intake pipe.

    24505575 - Fuel Pressure Regulator Hose. Again, cheap. Get a new one from the dealer.

    24504034 - Intake pipe to Plenum Gasket. This one costs $2.00 and it’s worth replacing right now because it gives you a good chance to clean the pipe, clean out the entry to the plenum, and have a good seal there.

    24504035 - Throttle Body to Intake Pipe Gasket. It costs $1.61, and again, worth doing and it gives you a chance to clean out the TB really well.

    ’96 PCV Valve

    ’96 Canister Purge Sensor, found bolted to the front of the plenum, passenger side

    Before I get into the steps, at this point some people consider moving their ICM and coils up to the passenger side of the intake like the ’96 have. I did this and I’m happy with it. Since it does not directly relate to the intake, I will cover it at the end of the write-up in an Appendix.

    Now, on to the swap!

    1) Remove the old intake by removing the seven (7) 10mm upper plenum bolts, the two retaining bolts on the back of the plenum, the brake booster hose, the EGR Valve and EGR backing plate/pipe, all the MAP vacuum connections, throttle cables, and loosen up the coolant hose connectors for the upper to lower coolant hose. Remove the upper radiator hose from the T-stat pipe on the lower intake. Disconnect the IAC, TPS, and IAT connections. Remove the upper plenum.

    2) Remove the twelve (12) 10mm lower intake bolts. There are eight for the coolant passages and four in the middle for the runners. Remove the intake and set it aside as you will need it in a minute. Remove the gaskets. Remove the old crankcase valley hose and install the new crankcase valley to PCV valve pipe.

    3) Remove the’ 92 rear cam carrier cover right away and replace it with the ’96 cam carrier cover. Four (4) 8mm bolts secure it.

    4) Clean the mating surfaces on the heads and intake of any debris or silicone. This is crucial as the new gaskets have far less rubber on the mating surface than the old ones do. Once that is done, install the new lower intake gaskets.

    5) On the old lower intake, remove the fuel rail by removing the four (4) 8mm bolts securing it to the intake. Remove the fuel injectors from the ’92 fuel rail by removing the locking tabs with a flat-blade screwdriver. They’ll come out hard, but make sure the O-rings stay on them and that they are undamaged. Disconnect the harness from the injectors by pushing the silver piece of wire in the connector toward the injector and pulling up on the connector. Do the same on the ’96 fuel rail, and install the ’92 injectors and harness onto the ’96 fuel rail.

    6) The thermostat is installed on the driver’s side of the lower intake and secured with two (2) 13mm bolts. If you plan on running a different thermostat, change it now. There is no room to change it later.

    6a) Notice the lower intake has a bypass on it that runs up to the throttle body to heat it. On my intake, the passage on the intake pipe for that was cut off, and instead I used a ¾” expandable rubber freeze plug that you can get at Advance Auto Parts in their HELP section to plug the bypass hole in the lower intake. This is not necessary, but then you have to figure out how to plug the end of it that is supposed to have a hose running back to the heater core. Since the ’96 coolant pipe already has a split off to run to the heater core, on a ’92 this extra one is not necessary. If your car is a summer car, I recommend plugging it (See Bypass Plug Figure).

    7) Install the ’96 lower intake. Use the two (2) locator boltholes to center the intake. I used tall cam carrier bolts to hold down the intake. Since these gaskets are thinner I torqued my lower intake bolts to 20 ft/lbs. Work from the inside out when torquing the bolts and recheck them once you’ve done them all. Install the upper plenum gasket on the lower intake.

    Problem: Before you can install the new upper plenum, you need to figure out what you’re doing with your rear spark plug wires. The new plenum is so massive in the back there is no room for the handles on the ’92 wires. You must either switch over to ’96 wires, switch the rear boots over to ’96 boots, or take some front ’92 boots and attach them to the back plug wires.

    Now the fun begins. The ’92 setup has a lot of extra things that the ’92 OBD I setup simply does not have. Examples are a canister purge vent, a MAF, a digital EGR, etc. So some things just don’t get hooked up, some you work around, and others you have to make work. The MAF sensor, for example, don’t even bother putting on because you don’t need it and the computer wouldn’t know what to do with it anyway.

    9) Start by installing the Plenum, Intake Pipe, and TB together as an assembly. Using the ’96 plenum bolts, two of them will have threads on top of them. One of them goes on the top row, driver’s side and that is what the plenum to intake pipe support bracket connects to. Cap it off with a 10mm nut. The other one goes to the passenger side on the top row and is very specific because it is the right length to fit in that hole. Torque the bolts to 18 ft/lbs. (See Figure 1)

    10) Time for some vacuum lines. Start with the brake booster. It connects to the wide mouth opening on the top of the air intake pipe near the plenum connection (See Figure 2). Next, connect the lower port on the canister purge sensor to the lower connection on the driver’s side of the air intake pipe by the throttle body. Take a piece of rubber hose and connect the upper port of the canister purge sensor to the other vacuum line that came attached to the vacuum line you just hooked up. The other end of that will connect to your canister purge line that hangs out by the cruise control and washer pump wiring. I don’t have a good picture of this one, so you just have to know what it is. (See Figure 5 for rough idea)

    11) Install the PCV Valve in the crankcase valley to PCV Valve pipe. There is a port on the rear of the plenum that the PCV valve connects to. (See Figure 3) To connect the fuel pressure regulator, the best thing to do is T it into the narrow mouth connector up where the brake booster line connects to the air intake pipe. (See Figure 4)

    12) Now the wiring. The factory harness has the length to get to the Idle Air Control motor, but not to the Throttle Position Sensor, so you will have to extend the wiring for it to reach the new sensor (See Figure 6). The connectors are the same. The EGR is not going to work even if it had the right connector because it is digital, so don’t worry about it. With a little maneuvering, the Canister Purge Sensor wiring will reach the new location, but the MAP sensor is an issue. You can either run a vacuum line from the map sensor over to one of the smaller connectors on the intake pipe and let it sit next to the canister purge sensor with the stock connector (what I did, see Figure 1), or you can run the wiring over to the new MAP sensor in the intake pipe and replace the connector with a ‘96 connector. Intake air temp should not be a problem, just put the sensor in line somewhere in your setup.

    13) If you use the ‘92 throttle cables, you need to find a way to route it so that it has no severe bends, because it will bind and keep the throttle cracked open slightly resulting in high idle. I fixed this by adding a return spring, but I will eventually get the ’96 throttle cables.

    If you did everything right, the car will run just like it did, but now be a lot easier to work on with a lot less things that can go wrong. And thanks to the longer runners, you have a lot more mid range and top end than you did before, and you saved about 10 pounds! You also now have the ability to add different and bigger throttle bodies. So far, I know that an L67 and a Northstar TB bolt right up, but I don’t know how your engine will respond to it so you try that out on your own.

    Appendix: There is nothing but advantages to relocating your ICM and coils. Some people don’t want to out of convenience and I respect that. I am providing this appendix for those that want to do it. Here is what I see as the main advantages:

    - ICM and coils not hanging out under a hot exhaust manifold
    - Far shorter plug wires, much less routing to do
    - Shorter wires mean less resistance; new style boots will actually keep crap out of spark plug holes
    - Easy access to coils and wires

    Here is what I see as the main disadvantages:

    - Things get a little crowded on that side of the motor, however if you are a DOHC owner you are used to that.
    - You have to reroute the ICM wiring and loom it

    If you do want to move the ICM and coils up by the intake, there are some extra parts you will need to get off your donor motor:

    ICM Support bracket
    ICM Aluminum Backing Plate that mounts to the support bracket
    ’96 Passenger side lifting point (has extra bolt hole for ICM)
    ’96 Wires

    Here’s how I did it (Reference Figure A1 for this section):

    1) Remove you ICM from its existing location by removing the four (4) 10mm bolts that secure the ICM aluminum backing plate to the block. Disconnect the wires and the assembly will come out as a whole.

    2) Get your hands on either a 5.5mm or American equivalent deep-well socket and some PB Blaster to get the coils off the ICM and backing plate. This is by far the worst part of the job because these bolts are always rusted in and very flimsy. They like to either round off or snap, and replacing them isn’t cheap. Also, it makes it a lot a fun to get everything apart, so be liberal with the PB Blaster and just go slowly. There are two (2) bolts per coil, one on each end. Once they’re out, the three pieces separate from each other, those being coils, ICM, aluminum backing plate.

    3) If you’ve had your motor apart before (like me), you know that one of the worst bolts in the whole motor is the one that holds the passenger side lifting point to the accessory plate. Which means to get it out, you have to take the timing belt cover off and then have the right wrench, star drive bit combo. So, since you have to replace it, if you don’t want to deal with that bolt anymore, cut the bottom of the lifting bracket off where the bolthole is for that bolt. Bolting it to the cam carrier and the accessory plate on top is more than enough should you ever have to lift the motor out of the car. But replace this bracket next.

    4) Now, install the ICM support bracket. One of the 8mm bolts on the timing cover plate lines up with the bottom part of the bracket; attach it there. The other main mounting point is the upper plenum where the ICM used to go. Now there are two (2) boltholes that line up. Bolt it down there.

    5) Install the ICM backing plate. Two (2) bolts secure it on the right edge of it along with some alignment dowels. It also bolts to the lifting point bracket with a captive nut.

    6) Install the coils in this order from the firewall forward: 1-4, 6-3, 2-5 (should your coils be numbered. Keep in mind that #1 is the piston right next to the ICM and #2 is the one directly across from it on the front bank.

    7) It’s up to you on how you want to route the ICM wiring. The biggest thing is pulling it out of the main loom and restringing it. The only wiring you have to modify is you have to cut the black/white ground wire and reground it up in the new location because it grounds to a stud on the block in the old location. You have to reroute the crank position sensor wiring as well.


    Check the photogallery link

    Attached Files

    • bszopi
      bszopi commented
      Editing a comment
      Nothing is stopping you from re-doing it.

      Sent from my DROID2 GLOBAL using Tapatalk

    • pocket-rocket
      pocket-rocket commented
      Editing a comment
      Originally posted by bszopi
      Nothing is stopping you from re-doing it.

      Sent from my DROID2 GLOBAL using Tapatalk
      I never said I wasn't going to since the pics were found Now I just need to get a camera (someone so politely broke mine :/) and get this done on my car. I would edit the article and sort the images, but I don't see an option anywhere to do so.
      Last edited by pocket-rocket; 07-18-2011, 09:06 PM.

    • pocket-rocket
      pocket-rocket commented
      Editing a comment
      Originally posted by pocket-rocket
      I never said I wasn't going to since the pics were found Now I just need to get a camera (someone so politely broke mine :/) and get this done on my car. I would edit the article and sort the images, but I don't see an option anywhere to do so.
      I see now, Mr. Pencil was hiding from me. I've also figured out how to work the images thanks to that article on how to write an article. I'll probably start monkeying with it on Friday since I don't work Fridays and my mind will be rested and it will be easier to think then.
    Posting comments is disabled.

Article Tags


There are no tags yet.

Latest Articles


  • LQ1 Service Bulletin 57-61-09 Lifter tick (cold)
    by Schurkey
    Dug up the GM Service Bulletin for "Lifter tick when cold", 57-61-09. '91 to '95 LQ1 (VIN X) The parts kit has been discontinued by GM long ago. My quest was to find sources for those parts; and complete the procedure on my '93 Lumina Euro 3.4 which was torn apart to replace the rear head gasket. There are three critical part numbers in the GM service kit (aside from gaskets and O-rings) required t...
    03-02-2012, 02:48 PM
  • 3.4 DOHC Heads on a 3x00 Block
    by bszopi
    Several people have talked about the possibility to use the 3.4 DOHC heads on the 3x00 engines. Some for performance, and some for replacment, where getting a 3.4 DOHC block might be difficult, but getting a 3400 (or even a 3100) block might be easier to come by. For these test fittings, I used a 1994 3.4 DOHC BLOCK, a 1994 3.4 DOHC REAR head, a 1999 3100 SFI BLOCK, and a 1996 3100 SFI head. This article is broken into 3 sections. The first section is BASIC COMPARISONS where I compare the BLOCK o...
    01-20-2011, 12:08 PM
  • 3.4L (DOHC) Specifications
    by bszopi
    06-15-2010, 05:56 PM
  • OBD2 Tuning 3.4 DOHC
    by Dave96z34
    The 97 4T65 in the Monte Carlo is almost bullet proof. I have been beating the crap out of my reman with my blower now for 2.5 years of daily driving vs the 60 NA that I couldn't get 1 year out of. 4 Trans in 50K miles. I'm a violent offender. Overfilling and royal purple atf are my secret. DHP will do 96 and 97 DOHC tuning, HPTuners only works with the 97 computer. 96 can not change line pressure, 97 can. 97 bin is double in size of the 96 bin. They changed every thing and it has every ...
    04-17-2010, 04:53 AM
  • 3.4 DOHC Pistons
    by SappySE107
    Here is the TRW catalogue spec sheet for the 91-95 as well as the 96/97 pistons.

    TRW 3.4 DOHC Pistons
    Silvolite 3.4 DOHC Pistons Notice that the 96-97 pistons don't have as much compression distance but also have a dome to them. I dont know the exact amount of compression loss you will get when using these pistons with the 91-95 heads, but it goes against the common belief that 96 pistons raise compression. The Silvolite pistons are the EXACT pistons used in the 91-
    04-14-2010, 01:23 AM
  • 96/97 3.4 DDOHC Intake Manifold Swap for 91-95 Engines
    by OldSkoolGP
    Pictures can befound here * Need to find this album * Having just completed this swap myself and being MORE than impressed with the results, I felt the need to write up how to properly do this swap so everyone else can do it easily: First off, here are the major components you will need from your donor motor: Upper Intake (Plenum) Lower Intake and fuel rail ’96 Rear Cam Carrier Cover (Valve Cover) Intake pipe Throttle Bo...
    04-14-2010, 01:20 AM