CC Build: Porsche 996 to LS1 Conversion

[gtxracer2]

Hi all - this is a continuation of my thread over on the other bulletin board. You can find the old thread here. This came from a request in this thread.

I'll start off from March 2020, where I had just finished the design of the 180 degree headers for this build. It's a 1999 Porsche 911 (996 variant for P car enthusiasts) and a 1999 GM LS1 from a Camaro. It's running a Terminator X kit at this time with drive by cable (DBC) throttle body. I also converted the car from the automatic Tiptronic (gross) to the 6 speed manual with limited slip (how they all should be). I also had to plumb my own hydraulic lines as the Porsche hydraulic lines were routed through the cab and it was a series of 12+ lines. I used two lines and bulkhead fittings in stainless which cost a lot less, looks better, and is less prone to leaks and trapped air.

I'll be copying and pasting a few of the posts here and then I'll get this thread up to date. It looks like most of you left off when I was putting in the electric power steering, so here goes:

__________________________________

The 180 degree headers have been ordered. I should see the first set in about 3 weeks. I threw on the bumper to measure for exhaust outlets, muffler placement, etc.. I think the Spintech mufflers should sound pretty good!

Maybe I should paint or coat the pan after all…

I threw in a new AGM Oreilly's battery and it CRANKS! No fuel pressure but it turns over great. I need to verify a few things, such as oil pressure and fuel pump operation before firing. I have some freebie LS truck exhaust manifolds on there for now.

Nearing the end of the electric steering conversion. I used RSR fittings since I didn't have time to make my own. They're a nice set for only $90. I also bought new Porsche O-rings made from organic unicorn toenails for too much money. I'm using PTFE 6AN lines and fittings (5/16 ID) for pressure with 6AN rubber hoses for return (3/8 ID). I have bought some nice bulkhead fittings and will run the lines near the brake master and pass through the firewall. Easy peezy.

Placement of the new pump. Way too tall. Bracket not really usable. I don’t want to drill down into the area it’s sitting on, that’s the fuel tank. More on how I mount this later on!

New bracket I drew up:

Cut on the Langmuir baby plasma cnc and bent:

I drew up this bracket. It needs a couple tweaks but came out great for a first draft. These TRW pumps are from a Vauxhall Astra and is the same pump as the Porsche GT3 cup pumps....but costs 1/10 of the price. As soon as I feel like sitting on my side for another 3 hours putting in the bolt on the rack that holds the fittings, I'll have this wrapped up.

Mega extension to reach said bolt, which stripped, but I got it out:

RSR Fittings and new SS bolt: Rebel S Racing (RSR) Steering Rack Fittings for elec. Pump – John James Racing

To do list is much shorter now:
Find lack of fuel pressure culprit and fix
Shift cables were wrong end type for transaxle end; too large, need earlier smaller versions or convert to heims
Fill and bleed coolant
Fill and bleed brakes
Bleed clutch
Tweak throttle cable; Only opens 75%
Mount Terminator ECU
Run Terminator lines permanently and route through interior
Reassemble interior
Tweak clutch pedal; it’s slightly out of position
Fab intake tube and tap for MAT sensor
Fab/buy PCV catch can
Hookup Porsche oil pressure sensor; extend wiring harness
Extend starter wire
Rework starter to alternator positive cable; route in cleaner fashion
Add 1 more block to chassis ground
Clean up wiring routes through car
Reassemble rest of the rear end of the car; crossmembers, sway bar, bumper, etc.
Final cut/fit of engine lid area
Test Drive!

 

[gtxracer2]

May 15 2020

Forgot to update this. Been a while!

Car starts and runs. Have to jump the fuel pump relay to get the pump to operate. Holds 58psi no problem. I need to find the correct wire in the loom to supply with 12v switched for relay to click over with the key. I have the starter wire ran and everything works as it should. Had to hookup a Holley 5v alternator trigger wire to the GM alt so it would charge the battery. New AGM battery from Oreilly's has been awesome for sitting then starting suddenly after weeks.

COVID shut down most of the midwest so the shop that was building the headers took a hit and had to close its doors for a while. They started cutting and bending tube this week so I should see the first set of headers in a couple weeks at most. I'm beyond stoked because I didn't think it would happen during this crazy pandemic nonsense where we think small business will survive 4 months of quarantine.

I will NOT be using SpinTech mufflers. I stumbled across an outdated webpage called Dr. Gas. The mufflers looked very similar to SpinTech but have some differences. I call them up and speak to the owner and original designer of the "Boom Tubes" and the SpinTech design. Evidently, he came up with that design and SpinTech and NASCAR ripped it off after the intellectual property rights expired, which I believe is 5 years. He now has a new shop setup in Utah and I'll be sourcing my mufflers through him. They should sound amazing and give the perfect tone. They're essentially built for this type of exhaust and scavenging specifically.

I had to redesign the exhaust headers a few times to meet all the bend criteria and fitment requirements. The exhaust now has expanded joints underneath that are offset so the headers are now a left and a right side. At this time, not using springs or other means to hold the halves together but that may change after the first prototype. I have a few people that will be running this exhaust in the 996 or 997 LS swap so I will have the headers, mufflers, and even clamps and mounts designed and ready for a bolt in LS swap exhaust system for Porsche 996 and 997 cars. Pretty neat.

Anyway, that's what I'm waiting on. I made a booty fab exhaust but refuse to drive it. It's annoyingly loud. I still need to bleed the clutch system and figure out why my clutch pedal spring seems to be backwards. I also need to bleed the cooling system. The electric steering is pretty much set up and ready for final painting, wiring, and final tightening and bleeding. It's basically there, just needs a little more finishing, but I'm waiting for the exhaust and I need to finish the backhalf of my TJ before continuing.

Smoked myself out of the garage upon startup but it was a fantastic feeling-

 

[gtxracer2]

June 10 2020

Sorry for the delays, I've been swamped. First set of headers are bent and tacked up. This set is going to the east coast for fitment on a few 997s and a 996.2. The second set will go to me to fit to my 996.1 and verify fitment before we produce the other sets. I've ordered my Dr. Gas mufflers and will be getting the 180 degree bends and turndown tips soon.

Anyone have a good source for stainless steel turndowns?

 

[gtxracer2]

July 14 2020

Lots of delays and slow downs. Reworking a tube to make it fit better in the crowded engine bay. COVID making things difficult again...should have something in two weeks which seems to be the theme of my exhaust work. At least I have the mufflers, the U bends are hydroformed and welded, and the turndowns are done. The hangers are modeled in Solidworks and ready for cutting and bending. They mount to the block and hold up the entire exhaust. The engine and complete exhaust drop out the bottom of the engine bay just like the M96 and M97 do in the factory 996 and 997 cars. This is now a 100% bolt-in solution to the LS swap in the 996 and 997 cars. I'm stoked on how well it's come out so far and can't wait to show the final version and get sound clips. I'm happy I'm still healthy and no issues due to COVID on that front so can't complain too much.

Pic of latest model-

 

[gtxracer2]

late July 2020

Update :D

Headers are installed, I had some troubles with first start and tuning. I also had interference with the starter that comes with the Kit Car Chassis LS to Porsche 996 and 997 adapter. I would NOT recommend buying this adapter. He used a cheap knockoff Chinese starter and it's proprietary to his plate. A factory starter with the bell on the tip doesn't fit. This means the LS3 starter that I used for design doesn't fit the adapter. I had to buy a PowerMaster 9509 starter ($$$$) with an open face (gear exposed). If I were to do this again, I'd buy the adapter from Stuttgart Muscle. It is machined for the LS3 Camaro starter and that's what I'll buy in the future the next time the engine is out. Lesson learned.

I tacked together the rest of the exhaust setup with stainless MIG wire and then sent them out to be TIGed. I wish I had just bought a TIG, hah! I can TIG weld decently, I was hoping this was faster and easier. Nope. 2 weeks now, still not done. Always something delaying me.

In any case, you can see where everything sits and how it will look, minus the hangers. The hangers are here and 80% finished, just a few more bends and then mount to the mufflers. This setup fits the 996 C2 platform without needing any additional welding which means that any 996 or 997 C2 swap enthusiast can do this in their driveway. It even has the O2 bungs and all clamps. The headers clear the 996 and 997 engine bay and firewall as well as the crossmembers. I'm super stoked on the fitment and how well it came out. Clears the AC compressor and alternator with room to spare. I've started it up and ran it with the temporary setup but will wait to post videos until I have the Dr. Gas mufflers back and everything is bolted up. This project is ready for it's first drive as soon as the mufflers are here. :D

Pics attached, hopefully this is what y'all were waiting for! ;) Excuse the mess!

 

[gtxracer2]

October-ish 2020

Thank you everyone for the kind words!

Here's a video of the headers in a LS7 swapped 997 belonging to TJ Kenny:

 

[gtxracer2]

October-ish 2020

I finally drove my LS1 swapped 996 for the first time. My alternator isn't charging, I think it took a dive after the first few startups. After I replace that and do some finish work, it'll be ready for it's first long drive to start racking up 500 miles to break in the clutch. After that and an oil change, it will be time to really start tuning this little LS1 and finish up the intake ducting, sensor placement, dash light and gauge fine tuning, and start some body and interior work. Of course, I'll put up a ton of videos for the exhaust sounds

I'll have a lot more updates soon, including posting this on the new site.

 

[gtxracer2]

Nov 2020

Couple more videos, second one is my car, the black 996. Enjoy!

 

[BCzuk]

Glad you brought it over here, great build!

 

[gtxracer2]

Jan-Mar 2021

Converted the car to DBW with LS3 throttle body. Should be starting it up this weekend for the first time. I rerouted the expansion tank lines, installed a 160 degree thermostat, rerouted a few other lines and wires, tidied up the engine bay quite a bit, and installed the P car oil pressure sensor and an Autometer 2259 temp sensor at the remote filter housing. I can keep an eye on oil pressure via the factory dash gauge and the 4.5" Holley screen will track the oil temp and even include it in the datalog. I had to swap the Holley Terminator X ECU with a Terminator X Max ECU and add the DBW harness. The main engine harness is the same, thankfully, so it made that part easy. I had the intake off and inspected all the sensors, connections, ports, and hardware - all seem good. A buddy with a LS3 996 with a dyno tune shared his idle tables so I can copy them to my tune and find this idle issue.

I bought a smaller Uni filter and a carbon fiber 45 deg intake elbow, should nearly get the deck lid closed now. For that that don't know, the LS3 intake has a shorter neck, so the intake elbows fit inside the engine bay much easier with less cutting. Wish I had known that sooner, I would have just bought a 6.0 or bigger block and ran rectangular port heads with LS3 intake. This FAST intake is awesome but the space restraints are crappy. I don't really want to swap engines now that it's all built and running but if I found a good deal on a L92, L99, or LS3, I'd take it. The cool part about the Holley system is I can quicky switch from 24x to 58x with one click and a couple harness changes. New USA made battery cable with stainless oil pan zip tie tabs I made for cable management. Came out pretty good IMO. Hoping the rest of the car comes out this nice! Looking at some new seats (mine are trash), then I'll work on a GT3 console delete, Continental period-correct stereo, and some other Alcantara bits to clean up the interior and start driving this daily.

For now, I'll just run the car with a deck lid that's not fully closed and learn to deal with it later. I also designed and made a heat shield just in case the headers get REALLY hot. A couple people were concerned with oil temp but there have been zero problems. I put a lot of thought and analysis in the exhaust system to mitigate these issues, but the armchair experts on FB know more than engineers these days, lol.

FWIW, these headers put down +20HP over block hugger headers on the dyno in a 530HP crate LS3. :D

 

[gtxracer2]

April-May 2021

Car put down 393rwhp with the ported LS2 intake. Pretty damn good IMO.

Then the car developed a knock. I have a new LS1 short block on the way and have begun pulling the existing LS1. One day this thing will be "done"....


_____________________

This is one of the last posts from the previous thead. I'll start posting new updates from here.

 

[surpip]

That is bad ass, its nuts how much that changes the sound of that motor.

 

[bdkw1]

Shit, I had forgotten about this! Glad you made it over.

 

[Blacksheep10]

Thanks for bringing us up to date. I’m headed back over “there” to see your cooling system a little better.

 

[budget76]

you're WAY past it, but seeing your extension snake makes me think of doing the clutch on my Miata. Wobble extensions were a godsend - you need a set, even a cheap set, if you don't have them yet. I was able to do every bolt on the top 180* of the bellhousing from behind the tranny

Wobble Socket Extension Set, 9-Piece

Amazing deals on this 9Pc Wobble Socket Extension Set at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

 

[gtxracer2]

Glad to have so many admirers here thanks everyone! I have a few more updates coming down the pipe.

I'll definitely grab some of those wobble extensions. I have a couple smaller wobblers and they're a godsend when working on this car.

 

[Scooter]

Thanks for this! Missed it something terrible from the old place.

 

[Kyle]

you're WAY past it, but seeing your extension snake makes me think of doing the clutch on my Miata. Wobble extensions were a godsend - you need a set, even a cheap set, if you don't have them yet. I was able to do every bolt on the top 180* of the bellhousing from behind the tranny

Wobble Socket Extension Set, 9-Piece

Amazing deals on this 9Pc Wobble Socket Extension Set at Harbor Freight. Quality tools & low prices.

www.harborfreight.com

A short quick ratcheting ratchet makes those bolts a piece of cake.

Also I got gear wrench brand wobble extensions on Amazon for less than the HF stuff. Open box for the win.

 

[gtxracer2]

In May timeframe of 2021, the car developed a rod knock on my way home from a local 100 mile trip. I was about 650 miles into the build when this happened and the knock was LOUD, coming from the bottom end. I have a few videos for people that love to cringe. I pretty much knew what it was, the damn rod bearing that the LS1 seller took off to show me "the bearings are good" and the bolts stretched. Not bad for a cheap LS1 I guess because I am still very much ahead of the cost of a new long block. I found a fresh 24k mile LS1 short block on ebay from a very reputable LS shop in Florida. They put in new rod and crank bearings as well.

Right before the rod knock, I swapped the Fast 92 intake for a ported LS2 intake I found through a couple contacts at LS1tech. I was scouring the interwebz for a stock LS2 intake that I would send out for porting when this perfect option showed up - a brand new ported LS2 intake for less than what I can sell my Fast 92 for. Badass! I swapped it over and it solved all my clearance issues between the LS3 DWB throttle body and the tensioner as well as gave me more space for my silicone elbow for the intake tube. Speaking of the intake tube, it's carbon fiber and the UNI filter make a nice finishing touch to the engine bay. Every time I lift the deck lid to show off the LS1, I get a nice "oooooh, ahhhhh" from the viewer. Same for the bottom of the engine bay which has the 180 headers. You'd never know a ~450HP LS1 with 180 headers is tucked under this ugly duckling of a Porsche.

Before I grenaded the first LS1, I had many Honda Civics, BRZs, BMWs, and even a few Audis begging me to race. Since my clutch was already broken in, I may have obliged a few times. The LS1 996 is still undefeated, if I had participated in such events.

Anyway, here's some pics of the intake swap!

 

[gtxracer2]

I put the car away for the summer and didn't touch it for a while. In WA, we only have 2-3 months of good weather, so instead of cruising the Porsche I spent time hiking, surfing, and spending time at the lake. It was awful.

But I did sit down and design these out of boredom. This would be for my Jeep TJ 4500 car but I'm selling it instead. I don't drive it and want to put that cash somewhere else, so these were never made. I have another 8-1 header design that I may design for the Porsche, we'll see. I still want to make a set of 8-1 headers some day and might just start a project just to make a set of 8-1s for it. I have a few other ideas for projects after the 996 is finished that involve some tasty V8 swaps that would drive the internet crazy. I'll save for those later as they're still in the works.

 

[gtxracer2]

As for the styling of the car, I'm still putting together the final goal for the exterior, but the interior is just waiting on funds, aka, whenever I get the nerve to drop $3k into the car that is already over budget due to killing my shortblock.


Right now, the plan for the interior is to use S8 seats from Braum in black fabric, a black carbon fiber D steering wheel from Carbon Mafia, and a shifter upgrade of some sort. Since the stereo system will be done soon, I'll focus on the rest of the interior later this winter. The seats are backordered until December, so I may just order those while I'm waiting. I attached a picture of these seats in a similar style in a 996.

For pics, you'll see a before picture of the center console area, then an after picture with the GT3 console delete and the new Continental 7416 head unit. That head unit doesn't have a subwoofer output, so I'm adding one. There's a 500w amp in the trunk and I added two 8" Memphis subs in a custom enclosure. I'll update the thread once I start building the enclosure, hopefully next week. It sits above the rear seats and makes a shelf in the back window area. I also have some Focal 4" speakers for the rear of the car and some Infinity Kappa 42.9i for the front 4" slots. This is a basic audio system, no factory subs or amps. Previous owner had a double DIN stereo but I want more leg room, hence the GT3 console delete and a 90s retro single DIN deck. I want this car to look like the pinnacle 90s Porsche with some kick underneath and subtle accents.

I'm not sure I mentioned, but this car is actually Rainforest Metallic GREEN. I'll be returning to that color eventually. For now, I enjoy the ratty sleeper look of a dinged up 90s Porsche 911. I attached photos of that color and a few wheel and suspension options I'm pondering. The last picture is a 997 but the concept would be the same. I'm a sucker for BBS e88s with the gold centers, but finding those for anything less than the cost equivalent of unicorn hair clippings and a jar of leprechaun piss is very difficult during the COVID car build frenzy.

 

[gtxracer2]

Now for the new LS1 short block...everything swapped over easily because I used ARP hardware and new gaskets. I did put new head gaskets and LS7 lifters in there as a precaution. I can't pull the heads easily with the engine installed, so I wanted the peace of mind.

I did have to cut the boss inside the valley for the LS6 PCV valley cover update. It was much easier this time around.

I fired up the LS1 last week and it held 52psi of oil pressure at idle.

 

[gtxracer2]

And lastly, here's some "beauty" shots of the car when cruising with the original LS1. All that remains is to bleed the clutch and tidy up a couple items and I can start the 500 mile bearing break in process again. I want to be able to cruise around for the rest of the decent weather we have here. I don't think I'll be driving it very much in the rain. Being rwd and ~393hp to the wheels, it doesn't get much traction after a good rain.

A friend of mine gave me some decent 996 headlights, so I can drive at night now too.

 

[dwygrsshpr]

A short quick ratcheting ratchet makes those bolts a piece of cake.

Also I got gear wrench brand wobble extensions on Amazon for less than the HF stuff. Open box for the win.

Even better than a short, highly toothed wrench is this. You can swing it like a regular socket wrench, but you can also twist/spin the handle without swinging to ratchet the socket around. I promise everyone will love it.

Amazon.com: Blackhawk GW-9946R Drive Rotator Ratchet, 1/4" : Tools & Home Improvement

Amazon.com: Blackhawk GW-9946R Drive Rotator Ratchet, 1/4" : Tools & Home Improvement

www.amazon.com

PS - Thanks for reposting your build!! I'm a pcar enthusiast (on #3) but not a snobby purist - I think this fawesome

ETA: Your picture of the green 996 with the gold BBS wheels gave me a thought. Why not replace your decklid with a fixed wing and hollow it out enough to clear your intake? You obviously can't use the retractable spoiler as is, so let that problem become an opportunity!

I am a sucker for ducktails on any 911 so that is where I started with a google search... Finding one with forward facing vents would be a bonus to suck in some of the low pressure (but markedly cooler) air coming off the roof

996 ducktail decklid - Google Search

 

[plym49.2]

1 - Frigging awesome! You have put 10 lbs of hot metal into a 1 lb bag!

2 - That car needs to be black.

3 - Please, for the sake of humanity, change that slim shady yellow crimp connector on the starter.

 

[DT75FLH]

Glad your posting here ....

 

[gtxracer2]

Even better than a short, highly toothed wrench is this. You can swing it like a regular socket wrench, but you can also twist/spin the handle without swinging to ratchet the socket around. I promise everyone will love it.

Amazon.com: Blackhawk GW-9946R Drive Rotator Ratchet, 1/4" : Tools & Home Improvement

Amazon.com: Blackhawk GW-9946R Drive Rotator Ratchet, 1/4" : Tools & Home Improvement

www.amazon.com

PS - Thanks for reposting your build!! I'm a pcar enthusiast (on #3) but not a snobby purist - I think this fawesome

ETA: Your picture of the green 996 with the gold BBS wheels gave me a thought. Why not replace your decklid with a fixed wing and hollow it out enough to clear your intake? You obviously can't use the retractable spoiler as is, so let that problem become an opportunity!

I am a sucker for ducktails on any 911 so that is where I started with a google search... Finding one with forward facing vents would be a bonus to suck in some of the low pressure (but markedly cooler) air coming off the roof

996 ducktail decklid - Google Search

Thank you, glad to be here :)

I like the look of ducktails on older 911s, especially the G bodies. It's growing on me for the 996. I initially had the same idea for the air intake, so I might be persuaded to try that once everything else on the car is dialed. I even started modeling an airbox that sat below the vents in a ducktail setup but there's too many other items to address right now. I'll keep this in mind! I am still on the fence between ducktail and a wing of some sort for downforce. At 140+ mph, it's a little squirrely and I'd like to get more downforce on the car. A front splitter and a rear wing might be necessities after a couple track days.

1 - Frigging awesome! You have put 10 lbs of hot metal into a 1 lb bag!

2 - That car needs to be black.

3 - Please, for the sake of humanity, change that slim shady yellow crimp connector on the starter.

Thank you :) Car will be green, there's enough black 911s and this is a rare color. What would you suggest for the starter excite connection? I haven't had any issues with this one but it's not 100% sealed if that's what you mean.

After some family events I'll be headed off to HD to get a sheet of 3/4" MDF for the enclosure build. It's nice weather this weekend so I'm going to delay that build until next week when it's not as nice.

 

[gt1guy]

Glad you brought the build here. I loved reading it at the other place.

So when will it get boost? Porsche's should all be turbocharged right?

 

[bdkw1]

That^^^^^^, twin turbski's would make exhaust plumbing much simpler.

 

[Grendel]

Nice to see you here.

I have an LT4 and a 996 waiting for me to finish some other projects due to this shazzbot here.