3.4l 996 intake manifold on 3.2S motor
Gang,
looking to install a 3.4 intake manifold in my 3.2 equipped boxster. I have the 987 airbox and maf, 996 throttle body, and customer intake tube already, so I'd like to put on the 3.4 manifolds. Also have 987 engine cover for more clearance. I think I understand the necessary steps, but correct me if I'm wrong: 1. Aluminum lower runners required 2. Plastic upper plenums 3. Fuel rail from a 996. Is this correct? install: 1. Drill and tap holes in heads 2. run shifter cables under plenums 3. ?????? Any other tips or parts necessary? thanks. |
i looked into this and i *think* that you may have to fabricate a braze-on or somesuch out of JB weld to create a place to drill and tap for one of the spots required to attach the lower runners to the head.
and yes, fuel rail has to change - mounting points are different. you could fabricate new tabs on the rail if you are ballsy enough to weld a fuel line, but note that you have to be bang-on as it is only the two fuel rail fasteners per side that keep the injectors in. |
thanks. I don't mind getting new fuel rails from a 996. I'm assuming they just bolt on in reverse?
never heard the jb weld sitch on one of the intake runners though. |
well, the fuel lines run over the transmission end in a 996, and if you put a 996 intake on a 986 you have to reverse the whole intake (to get the TB over the transmission end) so the fuel lines will be in the right place when all is said and done. you'll have to figure out how to adapt the 986 fuel lines to the 996 rails - porsche looks to use 1-time barbed fittings, but i've read that with heat you can get them off with no damage and then just hose clamp them when reinstalling (perhaps with some fuel-rated thread sealant?). you'll also have to extend your brake booster vacuum line to the other end of the engine.
you'll have to take a hard look at your head; here's a good pic of a 996 manifold; i think you'll find that there is no spot on the head to drill and tap in at least one of the required locations: https://www.ebay.com/itm/99-05-PORSCHE-911-996-CARRERA-LOWER-INTAKE-MANIFOLD-ADAPTER-PLENUM-9961101017R-/291880861094 |
I've put a 3.4 intake on a 3.2. I believe all I had to do was drill and tap the heads. I used the 3.4 fuel system but had to use the 3.2 boxster wire harness. I went over it on my build thread.
http://986forum.com/forums/show-tell-gallery/59449-woodys-build-thread.html |
i stand corrected! post 243.
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woody, awesome, thanks. how did you run the shifter cables and were there any issues getting everything to fit?
thanks. |
Would Cayman 3.4 runners be more easily adapted?
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I also have the cables over the top of the intake but on a 3.4L. I currently have a hard top on but it’s coming out off soon when my suspension shows up I can grab pictures of the routing if needed. This is a 3.4 swap like woodys.
Shawn |
sounds like over the top it is. If I have to lower the motor a bit, that should not be an issue when combined with the 987 engine cover.
thanks guys. |
Can you guys discuss what modifications were necessary to the fuel system and or 996 fuel rail to make this work?
thanks. |
Very interesting! Does anyone have power numbers or Dyno charts showing gains from using the 996 manifold on the 3.2? I'm really interested to see just how much power could be made with our 3.2. Given that the 2.0 in the 1967 911R & 904 made 220, why can't we get 350 from the 986 S motor?
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Woody posted some surprisingly good dyno results from bolt ons and ECU tunning. I would link it if I could find it. If we get into the heads and start doing it, how is the 3.2's propensity for head cracking mitigated? One could asks this for a total engine build as well. I feel your frustration ......I remember track days where I just couldn't shake old 993 on my tail... |
well, the size of runners on the 996 plenum doesn't seem to be bigger than that on the 3.2, i think the difference is length - the 996 units are longer, so you will see more of a venturi effect and better cylinder fill at lower rpms. they may actually reduce max hp a bit as the increased length would be seen as a restriction at wot, but raise the overall torque curve up a bit. and more area under the curve is the goal, not necessarily the max number.
if you think about it from a porsche design point of view, the only reason the boxster runners are shorter is so they could fit the engine in the car. |
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Your 220 HP in 1967 would probably measure under 200 HP using the SAE net ratings. You can read up about it here - https://ateupwithmotor.com/terms-technology-definitions/gross-versus-net-horsepower/ |
Don't quote me on this but I'm pretty positive the difference between the 3.2 and 3.4 are the case and pistons when it comes to the long block. The heads are mostly the same but the 3.2 has slightly less compression. The only real difference between the two is the intake, tune and exhaust systems. I didn't feel much of a difference when I went from a 3.4, to a 3.2 with the 996 intake, fuel, and custom exhaust made with the same diameter tubing as a 996.
The seals inside the valve adjusters were going bad in my 3.4. I put the 3.2 in while i fixed the 3.4. I almost considered leaving the 3.2 in but I had lots of $$$ invested in the 3.4, so I reinstalled the 3.4. My box made 279hp at the wheels with the 3.4 and my friend mad 249hp at the wheels with his 3.2. Here's the thread http://986forum.com/forums/performance-technical-chat/71568-two-modified-boxsters-dyno-2.html I contribute the difference in power between us to the length of the intake runners, mileage, tune and maybe the exhaust. I have a customer who owns a shop in Dallas. He claims to have made 300hp at the wheels with a 3.2. I tend to believe him as he works on some amazing vehicles and worked for Ruf at one time. |
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I've got the 74mm TB & a splitter in the intake (Pedros Garage). the rest of my intake is 3.2, but I know the TB made a difference. I wonder what an 82mm TB (GT3) would do. I've put this out there before, but my car made 244RWHP with all of the bolt-ons. |
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Anyone have this dimension at hand? It is probably the same diameter as the outlet of a 996 or 997 diverter tee.....recall way back when we first put 74mm TBs in and used reducers or did the stretch to make it fit with 3.2 boots. |
got a 996 setup for the cost of shipping, so I'm gonna give this a go.
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nice...would be interested in your drill set up for the additional holes.
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They are m6 holes that go down no more than 15mm. I intend to mark, center punch, and then drill using a drill block.
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If anyone is looking for a 996 intake, I have a full setup for sale, including throttle body
http://986forum.com/forums/boxster-cayman-parts-sale-wanted/74393-996-intake-manifold-air-box.html#post587539 I had planned to upgrade my Boxster with this setup, but the car just sold. I also have a 987 airbox in the Classifieds to work in conjunction with this setup |
so I believe I have a setup that will allow me to use the standard boxster fuel rail on the 996 intake and its shockingly simple. I'm not 100% convinced yet, but I'm pretty confident. Extending the vacuum hose is no biggie.
Did any of you 3.4 cable throttle guys have issues with the throttle cable being too short? |
right on. let me know what you are sorting out for the fuel rail (hopefully less work that running new fuel lines?). also advise if you'll be able to drill the heads without dropping the motor - thinking a drill block and a flexible drill extension?
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I would think there would be no issue drilling. I dont recall the fire walls getting in the way of the intake ports but i could be wrong
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So stock intakes are off. Bit fiddly but really no biggie. Fuel lines i think will be a non issue. The plenum will clear the 997s oil cooler. Vac line is a trivial change.
Drilling...well, it aint gonna be fun qnd im gonna have to move alternator and ac compressor i think, but ultimately if i mark well, center punch, and use drill block properly it should be fine. Prolly gonna end up with a right angle drill. Finally, id be amazed if the cayman cover clears. These plenums are seriously high. I may need to lower the motor about .5" Happy with progress so far |
thanks. keep the updates coming. i've got my 996 intake enroute and is the final step in the de-stupification of my 3.2. i'm thinking flex drill attachment or see if my dremel with flex attachment has the cojones to do the work. the intake i have coming (thanks halo) has fuel rails for a single line system so i am watching your fuel rail conversion with interest, otherwise i hope to use a mercedes 3.8 bar fuel filter/pressure regulator to convert my two line system. a quick seach shows that there are infinite adaptors to convert our fuel lines to barbed connectors for easy fuel line installation.
also interested in the clearance issue, and whether convincing the engine bay to let the intake fit, or dropping the motor is the soln. if you do drop, think about making the change to the rennline transmission mounts; they beome just incrementally more $ than getting the 993 mounts and really improve shifter feel. they come with longer studs that will take a spacer to let you drop the transmission to match the drop at the engine mount (which will also require a spacer and longer studs or bolts). |
I already have 993 rs trans mounts so no issue there.
Will update as i go forward. Waiting on gaskets now |
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Rennline also has longer studs you can put in if needed. My mounts arrived a little while ago.....they came unanodized which was annoying as all the images of the pieces showed a nice gunmetal finish Any problems with lowering the engine / trans at the back and not at the front? |
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Stock is 73mm, 996 is 91mm
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thanks man.....that is a very significant difference! I will be very interested in how this changes the performance of the engine.
I may be mistaken but I believe that this diameter is bigger than anything upstream on the 996 intake. This change may really enhance the effect of a larger TB, putting the relationship of throttle body diameter to plenum entrance at 80 to 90 percent while allowing for more air volume vs the smaller 3.2 plenums |
so I have the 987 airbox, custom i believe 3.5" intake tube, 996 throttle body, and headers/exhaust.
I think on a stock 3.2 this would have only minor benefits, but on an engine moving more air, it may be beneficial. You also pick up what looks like 2" or more of runner length, which should help lower rpm torque. I'm no expert but this is apparently something jake does on his motors. |
drilling has generally gone ok. I have 3 holes in, but I snapped a tap in one of them, so I'll need to find a solution there.
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He didn't offer any further explanation |
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