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Old 03-11-2016, 04:53 PM   #1
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3.4 engine swap Q&A

I'm very close to installing a 2001 3.4 into my 2000 Boxster S and I think I mostly comprehend what I need to do. I have the "101 project for your Porsche Boxster" book and I've also been surfing the internet on other engine swaps. I've got a few questions for those who might know.
1) What flywheel/clutch do I use? The 3.4 had a really good clutch on it and I'm hoping to reuse it.
2) I have the cluster, immobilizer and DME from the 996 cab. Besides running another wire to the cluster for the oil pressure gauge, it's just plug and play right?(using the 3.2 engine harness). There shouldn't be any reason for getting the 996 DME reprogrammed. The 3.4 DME will still think it's in a 996 cab?
3)I have a 987 aluminum engine cover. I won't need to lower the motor any to clear the 996 intake?
4)Is there a verdict on which fuel rail is better/easier? 3.2 or 3.4?

Thanks Woody
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Old 03-12-2016, 01:28 AM   #2
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Hi Woody I can shed some light on lowering the engine at the front. On my conversion the passenger side intake runner hits the opening (access hole) not the lid. It required four 3/4" spacers on the front mount. YMMV
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Old 03-12-2016, 03:46 AM   #3
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I think the Boxster S uses the same clutch disc as a 996 but the flywheel and pressure plate are different., so I expect you can use the 996 clutch flywheel complete
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Old 03-12-2016, 10:51 AM   #4
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1) What flywheel/clutch do I use? The 3.4 had a really good clutch on it and I'm hoping to reuse it.
This is dependent on which transmission you use. I foolishly ordered a 996 clutch but was using the 5 speed trans from my 99 Boxster. The teeth didn't line up so I had buy a regular 986 clutch which to my knowledge are fine to use with the increased power of the 3.4.
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2) I have the cluster, immobilizer and DME from the 996 cab. Besides running another wire to the cluster for the oil pressure gauge, it's just plug and play right?(using the 3.2 engine harness). There shouldn't be any reason for getting the 996 DME reprogrammed. The 3.4 DME will still think it's in a 996 cab?
I don't believe you'll need to reprogram the DME. I'm not sure about your MY but with my 99 harness I also had to route wires for the resonance flap in the intake.
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3)I have a 987 aluminum engine cover. I won't need to lower the motor any to clear the 996 intake?
I also bought a 987 engine cover. However the intake was making contact with the car and not the engine cover. I had to use a couple inches of spacers on the front engine mount. Try to lower the engine as little as is necessary because the engine lowers your ground clearance.
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4)Is there a verdict on which fuel rail is better/easier? 3.2 or 3.4?
I used the original rails because the 99 Boxster has a return fuel system, but the 99 996 did not. Your MY will be different than mine so you'll have to decide which one to use.

You've probably already seen it, but this pelican article was the most helpful resource I came across.
Porsche Boxster Engine Conversion Project - 986 / 987 (1997-08) - Pelican Parts Technical Article
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Last edited by soccerties; 03-12-2016 at 11:14 AM.
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Old 03-12-2016, 11:12 AM   #5
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Also I would recommend using a 987 intake if you can. Gives much more air to breath, bolts right in and only requires a simple modification to the intake. And do it before you put the engine in to save some knuckle skin.

987 v 986 Air box
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Old 03-12-2016, 04:13 PM   #6
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Quote:
Originally Posted by itsnotanova View Post
I'm very close to installing a 2001 3.4 into my 2000 Boxster S and I think I mostly comprehend what I need to do. I have the "101 project for your Porsche Boxster" book and I've also been surfing the internet on other engine swaps. I've got a few questions for those who might know.
1) What flywheel/clutch do I use? The 3.4 had a really good clutch on it and I'm hoping to reuse it.
2) I have the cluster, immobilizer and DME from the 996 cab. Besides running another wire to the cluster for the oil pressure gauge, it's just plug and play right?(using the 3.2 engine harness). There shouldn't be any reason for getting the 996 DME reprogrammed. The 3.4 DME will still think it's in a 996 cab?
3)I have a 987 aluminum engine cover. I won't need to lower the motor any to clear the 996 intake?
4)Is there a verdict on which fuel rail is better/easier? 3.2 or 3.4?

Thanks Woody
You should be able to use either Flywheel because both engines use the same crank, you have to use the Box 6-speed so you need a Box clutch if it's different from the 3.4.
Clusters changed in 2001 so I don't know what you have to do there, I would not change that until the engine is running.
Keep your OE DME it is the same as the 2001 just programed with 996 map. Engine will run fine unless you install the 987 airbox & bigger MAF tube of the 987. If you keep the bigger MAF you need to install the 996 DME program.
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Old 03-12-2016, 04:25 PM   #7
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Thanks guys! I saw a thread where someone was saying that all you need is the 987 cover and you don't need to lower the motor. I'm glad you both spoke up and let me know. Thanks again. Just a thought. Do you guys think you could hammer the metal where it hits far enough to clear or is spacers the only answer? I sure like the bottom of the motor higher.
I eventually want to get a light weight flywheel but it looks like I'll just buy a new clutch disc for the 3.4 clutch for now.
I have a 987 air box and an aftermarket intake I got from a member. I need to research on which is better.
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Old 03-12-2016, 06:05 PM   #8
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Not.
Mine fits with no spacers.
987s engine cover
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Old 03-12-2016, 06:08 PM   #9
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Possibly me
no spacers here
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Old 03-13-2016, 11:21 AM   #10
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Possibly me
no spacers here
You have a 99 correct? Did you lower the trans end or leave it? Are you using a 6 speed? I don't understand how you're not hitting the body without spacers.
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Old 03-13-2016, 11:41 AM   #11
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A 3.4 DME will have to be programmed to work with your immobilizer, and to enter your vehicle's VIN. The VIN is a problem during emissions testing when the tester sees a different VIN than your car's tag.

If you use the 3.4 DME and immobilizer, your key fobs will have to be replaced (unless you have the codes).
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Old 03-13-2016, 11:54 AM   #12
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Quote:
Originally Posted by soccerties View Post
This is dependent on which transmission you use. I foolishly ordered a 996 clutch but was using the 5 speed trans from my 99 Boxster. The teeth didn't line up so I had buy a regular 986 clutch which to my knowledge are fine to use with the increased power of the 3.4.
I have about 30000 miles on my 3.6 with the 2.5 5 speed clutch and tranny, no issues.
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Old 03-13-2016, 05:51 PM   #13
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I was at COTA today and ran into Brad Roberts. He's a car chief for one of the Cayman GT4's racing there and use to be big in the boxster scene. He's done a few swaps and said that because I'm using a 6 speed I shouldn't have any problem using the 3.4 clutch and flywheel. He also said that the 987 engine cover isn't normally enough to clear and I would either have to lower the motor a little bit or make some clearance in the sheet metal. He suggested I use the 987 airbox and that the dme, immobilizer, cluster, locks and keys from the 996 should work fine. Thanks for all your imputes.
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Old 03-13-2016, 09:04 PM   #14
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Sounds like you've got a good plan together. It's a great feeling firing up the new engine for the first time. Enjoy!
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Old 03-14-2016, 12:50 PM   #15
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Woody, you might look into swapping the 996 intake manifolds (you have to remove & flip them anyway) with either a 987 3.4 or 3.2 986 intake runners. It is the intake runner on the passengers side that will hit the chassis.
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Old 03-31-2016, 11:08 AM   #16
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I ran into a snag today. I'm using a 3.2 wiring harness and the coolant temp sensor wiring only uses two wires. The 3.4 coolant temp sensor uses 4. It looks like I can use the 3.2 temp sensor but how will that affect the 3.4 DME?
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Old 03-31-2016, 04:01 PM   #17
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Just got a call from a friend who says that he has used a 996 DME on a 3.2 that had the 2 prong sensor and he had no issues.
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Old 03-31-2016, 06:15 PM   #18
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Woody, I used the two wire sender on my 996 3.4 swap with my 1998 DME and it worked just fine. I used the 996 analog gauges from the 996 but kept the digital gauges from my original 986 and the analog temp. gauge worked OK.
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Old 03-31-2016, 07:24 PM   #19
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Woody, I used the two wire sender on my 996 3.4 swap with my 1998 DME and it worked just fine. I used the 996 analog gauges from the 996 but kept the digital gauges from my original 986 and the analog temp. gauge worked OK.
Thanks! It's good to hear another person confirming what my friend said. Makes me wonder what the other wires are for? I have 2 2.5's in my shop, and both had the 4 prong sender like the 3.4. I also have a few 3.2 wire harnesses, and they all had the 2 prong
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