Build Thread: '99 C2 996 LS1 Swap
10-23-2019, 07:53 PM
#1
Rennlist Member
Thread Starter
Build Thread: '99 C2 996 LS1 Swap
Hi everyone, I'm new to Rennlist. I recently purchased a 1999 Porsche 996 C2 with the M96 and Tiptronic combo. Unfortunately, the engine has a rod knock and needs to be rebuilt or replaced. I looked at a few options and made up my mind that this deserves a LS1/G96 swap. I drove across the state in the dead of winter last year to grab this car after it had been sitting a while. It's in rough shape in a few areas and has some beauty scars for sure. It definitely has been in an unreported accident as the front bumper is chipping and has yellow paint underneath and there's a couple small dents underneath the doors. Minor stuff, nothing too crazy. The interior needs a bit of help too, the carbon fiber Tip steering wheel is cracked and the seats have seen much better days. I would never really want an automatic sports car, so that's why I'm swapping to the 6MT at the same time.
I've LS swapped my Wrangler after extensively modifying it with coilovers, custom built 1 ton axles, custom front frame, and a 5.3L/4L80e/Stak Dana 300 combo pushing around 380-400 hp at the crank. I run a 3000 stall converter through this with quite a few coolers and love it. I miss my BMW 135i, so therefore the barely running 996 came home with me.
Here's a pic of the Jeep for reference. I built everything you see on it over the last 10 years:
Onto the Porsche build!
Dragging the 996 home for it's new life:
It was in rough shape after the blizzard coming home
Cleaned up, it's not so bad. Definitely a 10 foot car instead of a 1 foot car though...
I started searching and found a few things I needed to get started. I did TONS of research before deciding to go with the Porsche G96 6 speed manual with a limited slip. I also knew I wanted an aluminum block variant of the LS and found a disassembled LS1 waiting for pickup at a great price. I brought that home and cleaned it up. It's in fantastic shape! I sold the LS1 intake and 853 heads in favor of a Fast 90 intake and drive by cable throttle body as well as a set of 243 heads. I am reusing the hot cam that came with the LS1 for now.
I used new gaskets, seals, and ARP head bolts. It's 100% freshened up and ready to go! If anyone wants more details on the LS1 build sheet, just ask!
Finally, I was able to stash away the Jeep and pull in the German to the American garage for a teardown:
More to come!
I've LS swapped my Wrangler after extensively modifying it with coilovers, custom built 1 ton axles, custom front frame, and a 5.3L/4L80e/Stak Dana 300 combo pushing around 380-400 hp at the crank. I run a 3000 stall converter through this with quite a few coolers and love it. I miss my BMW 135i, so therefore the barely running 996 came home with me.
Here's a pic of the Jeep for reference. I built everything you see on it over the last 10 years:
Onto the Porsche build!
Dragging the 996 home for it's new life:
It was in rough shape after the blizzard coming home
Cleaned up, it's not so bad. Definitely a 10 foot car instead of a 1 foot car though...
I started searching and found a few things I needed to get started. I did TONS of research before deciding to go with the Porsche G96 6 speed manual with a limited slip. I also knew I wanted an aluminum block variant of the LS and found a disassembled LS1 waiting for pickup at a great price. I brought that home and cleaned it up. It's in fantastic shape! I sold the LS1 intake and 853 heads in favor of a Fast 90 intake and drive by cable throttle body as well as a set of 243 heads. I am reusing the hot cam that came with the LS1 for now.
I used new gaskets, seals, and ARP head bolts. It's 100% freshened up and ready to go! If anyone wants more details on the LS1 build sheet, just ask!
Finally, I was able to stash away the Jeep and pull in the German to the American garage for a teardown:
More to come!
The following 4 users liked this post by gtxracer:
10-23-2019, 07:59 PM
#2
Rennlist Member
Thread Starter
The LS1 build up:
I've been mocking up all of this in Solidworks CAD software and also designing a very early prototype of a 180 degree exhaust system to maintain a more high pitched and exotic sound to the car.
As for the LS1 to Porsche G96 adapter, I bought it from Eric at Kit Car Chassis with a stage 2 Spec clutch. He was nice to work with but it took about 6 weeks for the adapter and one of the bolts does not line up with the transaxle mount. I'd probably go with the Stuttgart Muscle adapter if I were to do it again but Eric does include a starter which is a plus.
Back of the LS1:
Adapter kit
Adapter installed with 4L60e dished flex plate used for starter engagement
SPEC Clutch which is a M96 996 variant, not a custom clutch
Note that the flywheel is 2 piece. First piece bolts the small adapter and flexplate to the crank (shown previously). Then the larger flywheel is bolted to that piece and the clutch afterward.
Assembled and ready to go LS1 to G96 transaxle
- 243 heads, dual springs, hardened pushrods
- Tick Performanece SNS Stage 2 cam
- Melling high flow oil pump
- All new gaskets, seals, etc
- ARP cam bolts, ARP head studs, ARP crank bolt
- Fast 92mm Intake
- PTM 92mm throttle body
- 42lb LS3 injectors
- Holley fuel rail
- Holley Terminator X engine management system
I've been mocking up all of this in Solidworks CAD software and also designing a very early prototype of a 180 degree exhaust system to maintain a more high pitched and exotic sound to the car.
As for the LS1 to Porsche G96 adapter, I bought it from Eric at Kit Car Chassis with a stage 2 Spec clutch. He was nice to work with but it took about 6 weeks for the adapter and one of the bolts does not line up with the transaxle mount. I'd probably go with the Stuttgart Muscle adapter if I were to do it again but Eric does include a starter which is a plus.
Back of the LS1:
Adapter kit
Adapter installed with 4L60e dished flex plate used for starter engagement
SPEC Clutch which is a M96 996 variant, not a custom clutch
Note that the flywheel is 2 piece. First piece bolts the small adapter and flexplate to the crank (shown previously). Then the larger flywheel is bolted to that piece and the clutch afterward.
Assembled and ready to go LS1 to G96 transaxle
Last edited by gtxracer; 10-23-2019 at 08:16 PM.
The following 3 users liked this post by gtxracer:
10-23-2019, 08:01 PM
#3
Rennlist Member
Thread Starter
Since I knew I'd need to do something for hydraulic lines, I researched the factory P car lines and finally figured out the entire interior has to be removed for the clutch lines to be installed AND they're very expensive and hard to source. No thanks. I'll be using braided stainless 3AN lines with these custom adapters I designed and had machined. Pretty slick, they have the same flare and geometry as the P car lines for 996/997 and insert into the Master Cylinder.
Then the 180 degree headers have gone through changes here and there. I think I finally decided on a front exit, toward the balancer. The early versions exited toward the transaxle.
More to come tomorrow!
Then the 180 degree headers have gone through changes here and there. I think I finally decided on a front exit, toward the balancer. The early versions exited toward the transaxle.
More to come tomorrow!
Last edited by gtxracer; 10-23-2019 at 08:21 PM.
The following 8 users liked this post by gtxracer:
capt s (10-29-2019),
cbracerx (03-02-2023),
Gingerman (10-23-2019),
JeremyLynn (02-01-2020),
jim010 (10-24-2019),
and 3 others liked this post.
10-23-2019, 08:02 PM
#4
Rennlist Member
Thread Starter
After finding a low profile motorcycle lift jack at Harbor Freight, I dropped the old M96 and Tiptronic out of the 996 donor. These engines are massive. I was expecting it after hearing the stories but this is a BIG setup. I can see how the LS1 would be lighter now that all of this is out.
Fresh slate, ready for the initial LS1 mockup:
Referencing this picture again:
I reversed the direction of the collectors to exit towards the rear of the car (balancer side). I've been doing a ton of research on 180 degree headers in a LS application. Most people do not like the sound with a crossover, which is shown below. I am leaning against it. Most of the best sounding 180 degree header designs are shorter with small or no mufflers. Take a look at the GT40 headers and you'll see what I mean. I also thought about using a muffler that has a dual in and dual out with an internal crossover but I doubt I'd like that after hearing the reviews on them.
It will be a bit of a mix and match experimentation for the mufflers and final output after the collectors. I don't want it to be irritating or loud. I'll have V band clamps after the collectors to make swapping easy. I may have to make a temporary exhaust while I experiment with placement of the AC, alternator, and hopefully a dry sump setup.
Shown above is all the components I've been managing and test fitting. A mechanical manually set tensioner with a Gilmer drive gear on the same pulley as the 6 rip serpentine belt, a 3 stage Aviaid dry sump pump, factory AC compressor, and factory alternator. I am likely going with a Nutter dry sump pump after talking with AC, the man that runs that small company out of Vancouver, WA. I will run 3 pickups out of a shallow pan but will likely design the headers to allow other pans as some fellow 911 LS swap guys have requested them. I will likely mount the dry sump pump on the same side as the water pump outputs and have it mounted high, off the cylinder head on that side. The motor mounts are directly bolted to the heads so I will have to manage that as well. I will also likely use a dedicated oil cooler with remote filter and a 3-5 gallon dry sump reservoir with a separate vent/catch can. Coleman Racing has a neat dry sump reservoir with built in cooler, filter, and oil level sight tube that I might try. The dry sump setup is a recent change so I'll have to tear down the LS1 for the new pan. I am still planning to use the Melling internal oil pump for pressure. This entire dry sump setup will cost less than half of most entry level kits.
Fresh slate, ready for the initial LS1 mockup:
Referencing this picture again:
I reversed the direction of the collectors to exit towards the rear of the car (balancer side). I've been doing a ton of research on 180 degree headers in a LS application. Most people do not like the sound with a crossover, which is shown below. I am leaning against it. Most of the best sounding 180 degree header designs are shorter with small or no mufflers. Take a look at the GT40 headers and you'll see what I mean. I also thought about using a muffler that has a dual in and dual out with an internal crossover but I doubt I'd like that after hearing the reviews on them.
It will be a bit of a mix and match experimentation for the mufflers and final output after the collectors. I don't want it to be irritating or loud. I'll have V band clamps after the collectors to make swapping easy. I may have to make a temporary exhaust while I experiment with placement of the AC, alternator, and hopefully a dry sump setup.
Shown above is all the components I've been managing and test fitting. A mechanical manually set tensioner with a Gilmer drive gear on the same pulley as the 6 rip serpentine belt, a 3 stage Aviaid dry sump pump, factory AC compressor, and factory alternator. I am likely going with a Nutter dry sump pump after talking with AC, the man that runs that small company out of Vancouver, WA. I will run 3 pickups out of a shallow pan but will likely design the headers to allow other pans as some fellow 911 LS swap guys have requested them. I will likely mount the dry sump pump on the same side as the water pump outputs and have it mounted high, off the cylinder head on that side. The motor mounts are directly bolted to the heads so I will have to manage that as well. I will also likely use a dedicated oil cooler with remote filter and a 3-5 gallon dry sump reservoir with a separate vent/catch can. Coleman Racing has a neat dry sump reservoir with built in cooler, filter, and oil level sight tube that I might try. The dry sump setup is a recent change so I'll have to tear down the LS1 for the new pan. I am still planning to use the Melling internal oil pump for pressure. This entire dry sump setup will cost less than half of most entry level kits.
Last edited by gtxracer; 10-24-2019 at 03:37 PM.
The following 2 users liked this post by gtxracer:
Hawkpilot6060 (10-27-2019),
JeremyLynn (02-01-2020)
10-23-2019, 08:58 PM
#6
Nordschleife Master
About time u got around to this 
Looking foward to the updates and I really like the clutch fittings.
Looking foward to the updates and I really like the clutch fittings.
10-23-2019, 09:07 PM
#7
Three Wheelin'
Awesome, love this kinda stuff.
Trending Topics
10-24-2019, 03:57 AM
#9
Rennlist Member
10-24-2019, 03:50 PM
#12
Rennlist Member
Thread Starter
Thank you everyone, I'm glad to finally be able to post the progress and start go over solutions to the packaging issues. Yes, I am also on the Facebook Porsche Swaps group, that's where I get a lot of info from. That group has been a huge help and I'm really glad it's around. I am looking to avoid all oil starvation issues with the dry sump setup to avoid another Apollo 911.
I'm hoping to position the LS1 in the car this weekend and start the process of getting the motor mount plates in position and mounted, get a plan together for the coolant lines, and start working on removing the AT brake pedal for the MT clutch/brake subassembly. All coolant, clutch, and misc lines will be AN fittings and higher quality braided lines, just like I did on my Jeep. It was definitely worth it in the end. I'll be using a Corvette LS3 accessory drive including water pump. I'll have to get clever with the water pump fittings and will take a similar route that Stuttgart Muscle recommends but with AN fittings threaded into the water pump outlets. I actually have nearly all the components to start the swap from AT to MT including CV axles, clutch/brake pedal assembly, shifter, shift boot, shift cables, and a few other bits. I also already have the Holley Terminator X kit waiting to be hooked up. I'll need to find a good source for key-on power if anyone has one to share for the swap. I also need to make a plan for the fuel return line since my LS1 is returnless. I used a Corvette regulator on the Jeep and might do that again and plug the existing line.
I plan to also steal the oil pressure, oil temperature, and engine coolant temp sensors off the M96 and adapt them to the LS1. The early LS motors did not require oil pressure signal to the PCM to start and run, so I don't even need the OEM GM oil pressure sensor, just the P car unit. The pre-2001 996 cars are not CANBUS so they can be easily "tricked" into displaying the engine data to the dash and gauges by adopting the sensors to the LS1 like I've mentioned. I'll still use the LS1 sensors for engine coolant temperature and oil temperature so I can utilize the 3.5" LCD included in the Holley kit as a secondary set of gauges to rely on. I can also store and change tunes on the fly with this setup which will be very handy for more aggressive tunes for track use. The Holley PCM also calibrates itself and learns on its own which is a huge bonus and makes initial setup very easy.
I've updated the last post that was reserved for updates with pics and info from the M96 removal and my dry sump plan as well.
I'm hoping to position the LS1 in the car this weekend and start the process of getting the motor mount plates in position and mounted, get a plan together for the coolant lines, and start working on removing the AT brake pedal for the MT clutch/brake subassembly. All coolant, clutch, and misc lines will be AN fittings and higher quality braided lines, just like I did on my Jeep. It was definitely worth it in the end. I'll be using a Corvette LS3 accessory drive including water pump. I'll have to get clever with the water pump fittings and will take a similar route that Stuttgart Muscle recommends but with AN fittings threaded into the water pump outlets. I actually have nearly all the components to start the swap from AT to MT including CV axles, clutch/brake pedal assembly, shifter, shift boot, shift cables, and a few other bits. I also already have the Holley Terminator X kit waiting to be hooked up. I'll need to find a good source for key-on power if anyone has one to share for the swap. I also need to make a plan for the fuel return line since my LS1 is returnless. I used a Corvette regulator on the Jeep and might do that again and plug the existing line.
I plan to also steal the oil pressure, oil temperature, and engine coolant temp sensors off the M96 and adapt them to the LS1. The early LS motors did not require oil pressure signal to the PCM to start and run, so I don't even need the OEM GM oil pressure sensor, just the P car unit. The pre-2001 996 cars are not CANBUS so they can be easily "tricked" into displaying the engine data to the dash and gauges by adopting the sensors to the LS1 like I've mentioned. I'll still use the LS1 sensors for engine coolant temperature and oil temperature so I can utilize the 3.5" LCD included in the Holley kit as a secondary set of gauges to rely on. I can also store and change tunes on the fly with this setup which will be very handy for more aggressive tunes for track use. The Holley PCM also calibrates itself and learns on its own which is a huge bonus and makes initial setup very easy.
I've updated the last post that was reserved for updates with pics and info from the M96 removal and my dry sump plan as well.
The following users liked this post:
JeremyLynn (02-01-2020)
10-24-2019, 04:31 PM
#15
Rennlist Member
Wow no more VARIOCAM ! What a shame.