Intake Manifold Upgrade?? 94 3100

[94CutlassSLCoupe]

Ok, here's the deal...my 94 3100 with only a little less than 21k on it is leaking oil at a fairly good rate...from the valvecovers and oil pump drive o-ring. However it consumed half a quart in about 800 miles, which i believe to be a bit high.

 

My sister's '94 3100 CS used a ton of oil and it ended up being the lower intake manifold gasket...we put a new one in along with the Aluminum Valve Covers and now it runs great.

 

That being said, are there any intake manifolds that will swap right on to the '94 3100 V6 (stamped rockers) without messing with the heads? Please don't tell me to mess with the heads or swap the engine as it only has 21k on it.

 

The manifold that I would think would be preferred is the '00-up 3100/3400 unit.

 

What kind of performance increase would I get?

[DiscoStudd]

Sorry, you would have to change the heads over to the 96-up roller rocker heads in order to get the 3400/'00-up 3100 intake manifolds to work (the stamped rockers bump into the LIM's intake runners.)

 

I've heard that the performance gain with the 3400 top-end swap is marginal, and definitely not as much as you'd gain by swapping a complete 3400 motor...

[Vegeta]

You can machine the manifold to clear the rockers. You would also need an EGR adapter for either 96-99 or 00-present.

[Brian P]

well to be honest, I noticed that my '95 heads, the intake ports were in an ever so slightly different spot than the roller heads I installed. I compared them by using the new GM intake manifold gasket meant for a '99+ 3100/3400.

 

As for it being worthwhile, yes it definetly is. But you won't get "3400" power without the little extra from the displacement. Test drive like a '00+ Buick century to get an idea of what the engine will feel like. The biggest difference is past 4000RPM, below that is about the same.

[terryk2003]

well, my mom has a '02 alero with the 3400 and that thing RIPS...it'll SMOKE the tires from a stop...my 3100 in my cutlass isnt even a close comparison...but, i guess i should also think about the fact that my cutlass is heavier...SO, even if i do a 3400 swap, it prolly still won't feel as fast as the alero... :?

[94CutlassSLCoupe]

I really don't understand the reason why someone could not just swap on the roller rockers to the old heads.

 

I'm not expecting to get the 3400 power out of just swapping the manifolds...Lets say if I could get this engine from its stock 160hp to lets say 170-175 (about that of a 2000-up version).

 

I've driven a 2002 GP SE with the 3100, but i'd say that the 2002 car is a bit heavier since it has dual airbags and the extra wiring/plastic/unsprung weight (Brakes, Rear Suspension).

 

I did a little reading on 60degreev6 and the 2000-up LIM looks like it might clear without modification. The EGR adaptor isn't a biggie since i could probably make one at work (we have shop tools) if I had to.

[Brian P]

The roller rockers don't bolt onto non-roller heads. The roller rocker setup doesnt use the metal guide plates to keep the pushrod in its place and "align" the rocker arm. Rather, the roller rockers have a pedestal that fits into a machined "notch".

[Vegeta]

If you can make a 2000+ EGR adapter for bolting the older vacuum/digital EGR that was used till 95, and keep the price down on a bulk order, let me know.

 

You can use aftermarket roller rockers but its a bit of work to use them. Harland sharpe is the brand I believe.

[GP1138]

I am wanting to do the same swap, but I wanna do the heads too. I'd really like to find the roller rockers. I wish there was a step-by-step FAQ or something.

[DiscoStudd]

Digging through my HDD, I found the write-up that used to be up at 60*V6.com (when they were part of GMForums) that I saved when I first pondered the swap a couple of years ago.

One of the most popular modifications right now is the 3400 top end swap onto a 3100. The 3400 (along with the 2000+ 3100s) have much larger runners than the 94-99 3100, thus allowing for increased airflow into the engine. Stock 3400 plenum and manifolds also benefit little from increased PnPing, although gasket matching is recommended. Also, if you plan on installing a 62mm TB with this combo, you will need to port out the plenum opening to match the 62mm TB size. With that all said, let's get to the procedure!

 

Preliminary Steps

 

There are a few things that need to initally be done before attempting this swap. To save time (and possibly even money), do these steps first before tearing into the engine.

 

1. First of all, I recommend 97 3400 parts from the minivans (Venture, Silhouette, etc). This way, people with a 96-99 3100 won't have to worry about any EGR issues. Also, if you are buying new from GM, they are cheaper than the 00+ units. Why? Who knows... Here are the part numbers and prices for the units:

 

Upper Plenum : 10234990 [$126.08]

Lower Manifold : 24508396 [$61.04]

These prices are from GMPartsDirect.com. Dealership prices will most likely be higher.

 

2. Once you get the parts, you will need to make a couple modifications to the lower manifold. The first thing is the heater coil pipe fitting. The 3400s use a pressure fitting, whereas the 3100s use a screw in fitting. This is easily fixed though. You will need a 1/2"NPT pipe tap. Just tap out the coolant pipe hole. Be careful when doing this. You don't need to go all the way down either. I did this on my first manifold, and ended up getting the tap stuck inside the thermostat housing. I attempted to back the tap out, only to destroy all the threads that I had just created. If you get about 3/4 of the way down, you should be fine.

 

 

 

3. The next step is more of an observation step, although action may need to be taken. I found out the hard way that regular stamped rockers will fit the 3400 lower manifold. This is due to the larger runner size reducing the distance between the manifold and the rocker. I have included several pictures below which illustrate what to look for. If your lower manifold DOESN'T have the grindings from the factory as seen in the pictures, you will need to add them. So goto the next step... If your manifold has the stock grinding, you can skip the next modification.

 

 

4. If your manifold doesn't have the ground down areas from the factory, you will need to grind these areas down. NOTE: This should only be required for those people not having roller rocker heads. I will mention this again during the actual installation phase, but make sure you check clearances with a feeler gage before final assembly is done. Even after I ground down the manifold the first time, I had to go back and grind somemore becuase it was still touching. With that said and done, I used a die grinder to grind down the areas shown. You will most likely have to get down ~1/16" to 1/8" in order for everything to clear. Take your time while doing this and don't try to do too much at once. I have already talked with 1 person that sent the grinder bit through the runner . There should be 4 areas to grind down. And here is what it should look like when done:

 

 

And here is what the front side looks like from the factory. Notice how the front side actually requires more grinding than the back side. I noticed this with the one I modified in that I needed to take more material off the front side after checking clearances, whereas the back side cleared fine.

 

5. The final step in the preliminary phase is the EGR adapter plate. It is once again only for those having a 94-95 3100 initially. For more info on the EGR adapter, check out the EGR Adapter Procedure.

 

 

 

With all that said and done, its time for the installation, right? Well, almost... at this time, you might want to do other modifications to the manifold and plenum. This could include gasket matching the runners, porting out the plenum for a larger throttle body, or possibly even painting or powercoating the pieces. All of that is up to you. For info on doing such items, check out the how-to areas. Not all of them are actually covered, but some basic PnP info is, which can then be applied to the manifold and plenum. If you still have some questions, I would prefer you bring it up on the 60DegreeV6 forums (located at GMForums.com), but I will also try to answer any emails I recieve.

 

Ok, now its time to get on with the procedure!!

 

3100 Intake Manifold Removal Instructions

 

Removal of the Upper plenum

 

Relieve fuel system pressure

 

Remove your air cleaner assembly (stock, CAI, etc..)

 

Remove the EGR assembly from the plenum. Unplug the EGR plug and set the EGR aside.

 

Disconnect the following electrical connectors:

 

 

Spark plug wires

 

Throttle Position Sensor (TPS)

 

Idle Air Control (IAC) valve

 

Injector Harness

 

MAP Sensor

 

 

Disconnect the following vacuum lines:

 

 

Vacuum modulator

 

Fuel Pressure Regulator

 

Brake vaccum pipe

 

PCV

 

 

Undo the ICM from the upper plenum. If removing lower manifold as well:

 

 

Unplug 3 electrical connectors

 

Remove remaining bolts from ICM brakcet and remove from engine. You will also remove the EVAP canister purge solenoid at this time.

 

 

Remove the MAP sensor from the upper plenum

 

Undo electrical connections to the alternator (1 plug and 1 bolted wire) and remove alternator.

 

Remove 12 (6 for 3400) bolts from the upper plenum (7mm wrench)

 

Remove the upper plenum from the engine

 

 

Removal of the Lower Manifold

 

 

Drain and recover coolant

 

Remove the serpentine belt

 

At this time, it is necessary to support the engine in some way, either with a jack and block of wood under the oil pan or an engine hoist

 

Remove upper engine mount

 

Undo power steering pump (3 bolts accessible through the pulley) and set off to the side. It is not necessary to undo any of the fluid hoses from the pump.

 

Undo coolant bypass line from water pump

 

Remove radiator hose from thermostat housing

 

Undo thermostat housing (This can just be set of to the side with the bypass line still connected)

 

Remove valve covers

 

The fuel rail can be done 2 ways:

 

Ensure injector harness is unplugged

 

Remove fuel lines from fuel rail. Fuel will leak out of the rail, so be prepared to have a rag ready to keep the fuel spread to a minimum. OR

 

Remove fuel rail from lower manifold and set of to the side. To do this, undo the 2 bolts holding the rail to the lower manifold. Then carefully pry the injectors out of the lower manifold. This can be done with a screwdriver or small pry bar gently lifting up on the rail in the vicinity of each injector. Once all are undone, set the fuel rail off to the side (limited by the fuel lines)

 

 

Remove 8 lower manifold bolts

 

Remove lower manifold from engine

 

 

If replacing the lower manifold gaskets at this time:

 

 

Loosen rocker arm nuts

 

Remove pushrods. IMPORTANT!! Keep the pushrods organized. They must go back in the same position that they were removed from.

 

Remove lower intake manifold gasket

 

Clean off all of the gasket mating surfaces (including the gap between the heads on the block). Ensure all old RTV is removed from all of the surfaces.

 

Clean off any excess dirt, oil or other materials before reinstalling new gaskets and RTV

[GP1138]

Does it actually stop there? Or is there more and your post got cut off?

[DiscoStudd]

I double checked and that was the end of it...