CC Build: Porsche 996 to LS1 Conversion

[dwygrsshpr]

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.

I'm guessing you already know this but you have to be careful about aero and downforce. Porsche engineers know a thing or two and there have been instances of folks trying to get trickier than them with bad results when driven in anger. You're already tail-heavy* with a lot of power going to the pavement. I would suggest the chin splitter first and see what works.

I probably missed this from the previous board, but what are y'all doing about radiators with this transplant? Obviously up front, but how are you fitting it? Plumbing? Are you doing any oil cooling?

Brake upgrades? And speaking of, what kind of rear tire are you going to size?

I'm impressed about the work you did with the electric steering box - I have the hydraulic steering in my cab disconnected to give a heavier weight to the wheel - only a minor inconvenience in parking lots.

*How much more (or less) weight is the new powerplant compared to the M96?

 

[ORTitan]

Remember seeing this on the other site. Excellent work! Can you elaborate a little more on the electric power steering pump? What years and what needed to happen for the wiring? Thanks!

 

[surpip]

.

*How much more (or less) weight is the new powerplant compared to the M96?

"The truth is, at 450 pounds with all the accessories, the all-aluminum LS2 weighs nearly 50 pounds less than the 3.4-liter flat six and 140 pounds less than an engine out of a 911 Turbo from the same era."

 

[gtxracer2]

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?

Hah! Yeah there’s been a couple builds with turbos - but you have to use a Porsche turbo transaxle. The non turbo transaxles can barley hold 500hp. A turbo transaxle for these cars is 8-15k vs 2k for a non turbo transaxle. Not worth it in a car that’s meant for twisties IMO.

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.

Thanks! There’s a guy that swapped a LT4 into a 997 somewhere on the east coast. I can dig up his build thread if you want.

I'm guessing you already know this but you have to be careful about aero and downforce. Porsche engineers know a thing or two and there have been instances of folks trying to get trickier than them with bad results when driven in anger. You're already tail-heavy* with a lot of power going to the pavement. I would suggest the chin splitter first and see what works.

I probably missed this from the previous board, but what are y'all doing about radiators with this transplant? Obviously up front, but how are you fitting it? Plumbing? Are you doing any oil cooling?

Brake upgrades? And speaking of, what kind of rear tire are you going to size?

I'm impressed about the work you did with the electric steering box - I have the hydraulic steering in my cab disconnected to give a heavier weight to the wheel - only a minor inconvenience in parking lots.

*How much more (or less) weight is the new powerplant compared to the M96?

Thanks! The 996 and 997 have radiators up front as they’re water cooled cars from the factory. Mine has a third radiator in the center because it was a Tiptronic car originally. My LS1/6MT setup weighs 70-100 pounds less than the M96/Tiptronic. I can dig up the proof but I could care less at this point since the total weight of the car and it’s distribution is more important to me.

Not sure really what you want me to do about worshipping the Porsche aero gods but I’ll do my best I studied flight mechanics and have some experience with aero so maybe I won’t die from adding a splitter and a wing like you claim.

Remember seeing this on the other site. Excellent work! Can you elaborate a little more on the electric power steering pump? What years and what needed to happen for the wiring? Thanks!

Thank you. The pump is from a Vauxhall Astra. It’s essentially the same pump as the GT3 cup cars. Electric powered hydraulic pump. I’ll get the details for you but the pumps are becoming hard to acquire. I bought mine from eBay for less than $100 shipped from the UK. Mine is from 2000 - 2004 but I believe there are other years with compatible specs. You can also use a MR2 or Volvo pump, they’re similar.

"The truth is, at 450 pounds with all the accessories, the all-aluminum LS2 weighs nearly 50 pounds less than the 3.4-liter flat six and 140 pounds less than an engine out of a 911 Turbo from the same era."

This.

 

[dwygrsshpr]

I wouldn't have guessed that the V8 weighs that much less, hence my question. But that is a good thing and as you say overall distribution is much more important. And, not saying any aero treatments would kill a bus of nuns, just a lot more voodoo involved than people think. =) sounds like you got a good bead on it (not surprised).

Regarding radiators - you're just tying into factory? That makes it simple - and didn't realize the tip cars had an extra rad (cooler for transaxle?)

 

[gtxracer2]

I wouldn't have guessed that the V8 weighs that much less, hence my question. But that is a good thing and as you say overall distribution is much more important. And, not saying any aero treatments would kill a bus of nuns, just a lot more voodoo involved than people think. =) sounds like you got a good bead on it (not surprised).

Regarding radiators - you're just tying into factory? That makes it simple - and didn't realize the tip cars had an extra rad (cooler for transaxle?)

Me either! I thought the LS1 would be more weight than the M96. There's plenty of purists online that argue the opposite, but there's now dozens of people that have weighed their M96 and their LS variant with the same results - LS is lighter. Now, being taller, the LS may have a higher CoG but the increase in power is overwhelming that small detail.

Thanks for the heads up on aero, I'm essentially going to copy a working setup and tweak from there. I'm mostly worried about my rwd car sliding off the corners at the track

Yup, Tip cars have a third radiator since the Tip transaxle has a heat exchanger. Tied into factory and I have new fans and resistors to refresh the cooling system completely. The fans activate from the DME reading the P car water temp sensor in the LS1 head. If this isn't sufficient I'll make some changes but no problems from others with this setup.

 

[dwygrsshpr]

Some unsolicited 'light' reading on aero if you'd like. I advise an FSAE team at my alma mater and we send the students down the rabbit holes created by Professor Katz's work. If anyone has trouble falling to sleep at night, I recommend the second file to put you right out.

 

[plym49.2]

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.

Green is cool. Don't use those old-fashioned crimp connectors. You can get them with solder and shrink tubing preloaded - insert wire, heat with heat gun, solder flows and shrink sleeve shrinks. Waterproof and doesn't look like something on a hillbilly's wood chipper.

 

[gtxracer2]

Some unsolicited 'light' reading on aero if you'd like. I advise an FSAE team at my alma mater and we send the students down the rabbit holes created by Professor Katz's work. If anyone has trouble falling to sleep at night, I recommend the second file to put you right out.

Thanks for this, I'll be doing some reading!

Green is cool. Don't use those old-fashioned crimp connectors. You can get them with solder and shrink tubing preloaded - insert wire, heat with heat gun, solder flows and shrink sleeve shrinks. Waterproof and doesn't look like something on a hillbilly's wood chipper.

Ah, I see. I can pickup some of those so your eyes don't bleed when I show pictures of the starter and headers this winter.



Whoever suggested a duck tail might just get their wish....it's growing on me.

Probably this one:

CSR Carbon Ducktail - RPM Technik - Independent Porsche Specialists

All ducktails are made to order so estimated timeframe is up to 3-4 weeks. We do carry a limited stock of 996 ducktails so delivery times may be quicker. For more information please contact [email protected]

rpmtechnik.co.uk

 

[gtxracer2]

Subwoofer box coming along. 1 cubic foot volume for the twin Memphis 8" subs. 500w amp in the frunk. Also another duck tail photo that I liked (photoshop from an IG friend)

 

[WaterH]

Looks great! I don't know about the duck tail. It does look a lot better in dark color. I think you said you're going dark green, so might be OK.

 

[XtremeJ]

losing or damaging the front plastic bumper trim / air dam, calling it a splitter is generous, on a 997, or the 991.1 and .2 Cup cars is something easily felt by the driver (car definitely exhibits more understeer). We used to carry half a dozen spares and treat them as consumables.

There is a company that makes fancy carbon versions for the street posers, who usually rub them against the curb or parking stops. If I remember they ran almost 1K compared to the $200 odd for the OEM plastic version. I would also consider adding vertical fences at the front edge of the front wheel wells to generate more downforce, should be able to get them through Porsche motorsports as they were OEM on the Cup cars. You can also trim the fender liners to encourage the air to exit the front wheel wells, and reduce lift. Make sure the OEM floor panels and covers are servicable, known source of dirty air.

I would tame the rear end for track days through rear toe - in, and rake. The whale tail / duck tails, while looking cool definitely move the aero center of pressure rearwards over 85 mph, and change the balance of the car substantially especially through high speed (90 mph plus) turns. If you do choose to add any rear wing, you are going to need to add a ton of rake to dial out the understeer / push. Likely not noticeable on the street, or even street tires, definitely a concern on the track. Glad you made it over here, enjoy this thread.



The Katz Race Car AeroD book is pretty much industry standard - but don't waste your time and try to re-invent the wheel (or in this case wing) either, the engineers at Porsche really do know their stuff. If you want to see wild and wacky aero, most of which is useless just visit a PCA event. Decent driver in a stock car will still be quicker than most drivers with several tens of thousands of $$ who have every carbon appendage you could imagine.

But I prefer a sleeper look anyway.

 

[Gots_a_sol]

07 cayman local to me with a fragged engine. If I didn't have so many projects already going this seems like a fun one

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[gtxracer2]

Been slowly making time for the Porsche. Subwoofer box is nearly done. Needs final seal, finish sanding, and paint.

Tried bleeding the clutch again tonight. I hookup the Motive pressure bleeder to the master, pump to 20psi, have a helper push the clutch pedal down, then release the bleeder screw at the slave. Do this over and over, no bubbles. I can shift gears when the car isn’t running, but as soon as I start it, can’t put the car into gear. Definitely seems like I’m not getting hydraulic pressure to the slave. I hate bleeding

Fresh 130 amp alternator installed for the extra power consumed by the amp and subs.

 

[Kyle]

I follow a group on FB and someone makes a 8 into 1 exhaust for a 996/997 v8. Sounds unnatural.

 

[gtxracer2]

I follow a group on FB and someone makes a 8 into 1 exhaust for a 996/997 v8. Sounds unnatural.

Do you have a link? I saw one for a Cayman but not a 996/997.

 

[gtxracer2]

Update: Still can't bleed the damn clutch, sub box is nearly done, had to swap spark plugs yet again because the Terminator X dropped the tune when the battery was disconnected and the base tune has so much fuel it fouls plugs after a few startups.

 

[LunchBoxFab]

great build.

 

[budget76]

there's a roller e46 M3 chassis on Bimmerforums right now for $4500. Every time I see one I dream of the same type of swap, then realize I'm way too cheap to actually pull the trigger

love how stuffed in the Ls looks in the 911's. Hoovie on Youtube just got his back working again, though i can't say i watched the whole video about it

 

[XtremeJ]

07 cayman local to me with a fragged engine. If I didn't have so many projects already going this seems like a fun one

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Fun? definitely not, the Cayman sucks for engine and gearbox changes, unless you are the size of a 12 year old chinese kid

the 9xx's on the other hand, we had a engine/trans change down to 90 mins with 2 x experienced race mechanics using the onboard jacks (double high) and a harbor freight lifting table - GT3 Cup car

We did do a precautionary transmission change on a Cayman at VIR in 2017, and it took 3 of us from 6 pm until 3 am. All because the factory update on the axles had been missed - axle reaches lower limit of travel when curb hopping on track, and can put a side load on the transmission. A simple spacer cures this.

Unless the Gayman was free I guess?

 

[XtremeJ]

there's a roller e46 M3 chassis on Bimmerforums right now for $4500. Every time I see one I dream of the same type of swap, then realize I'm way too cheap to actually pull the trigger

love how stuffed in the Ls looks in the 911's. Hoovie on Youtube just got his back working again, though i can't say i watched the whole video about it

Vorschlag (sp?) used to make a Ls into E46 kit that made it as close to bolt in as you could get.

Probably cost what that roller is listed for though.

 

[budget76]

Vorschlag (sp?) used to make a Ls into E46 kit that made it as close to bolt in as you could get.

Probably cost what that roller is listed for though.

it looks like they still do for all the hard parts. and yeah, a couple thousand. I think they figured out the electronics in teh past but doesn't look like they sell any harnesses or anything.

derail over, i may get banned if i keep talking a different German brand in this thread

 

[gtxracer2]

I finally bled the clutch. I think the clutch disk may have stuck to the flywheel or something similar. I had to drive the car to get it to cooperate. It seems to be getting better each time I drive the car but the shifter also seems to be the culprit. I've never liked how this 996 shifter feels. I've heard good things about the shifter kits and even the 997 shifters but I think an entire aftermarket shifter and cables will be in the near future.

The subwoofer box is about 90% complete. I need to do the final sanding and painting. To make sure this was all worth it and it worked well, I wired up the subs and installed the box. I finished wiring the amp and routed all the wires through the cab, hidden behind the trim pieces. Can't even tell it's there. I'll be making mounting plates for the box to tie into the rear set belt studs to make sure the box doesn't try to donkey punch me while I'm braking hard in corners. The ininity kappas, focals, head unit, and these 8" memphis subs sound GREAT together. I had to piggyback the rear speaker signal to a low signal converter for the sub input since this Continental head unit doesn't have sub outputs. I still need to find the trim piece for the HVAC control locations but otherwise the GT3 console delete and stereo refresh are done.

I think the factory 996 power recline in my seats finally broke. Someone really abused this interior...these seats have seen better days but there are a few other areas that need help. I'll keep this thread up to date as I finish some of those bits. I also put the OEM exhaust shielding back on the car and buttoned up the frunk with all the panels, lighting, mats, etc.. This car will probably be stored for the rest of winter but I'll bring it out for sunny days here and there. If I get around to it and feel like spending the money, I'll order the new steering wheel and Braum seats soon. Overall I just want to DRIVE the car for a while until I know exactly what else I want to change.

 

[gtxracer2]

I forgot to mention I was loaned a e92 M3 from a friend. He's out of country for a few years and handed it over to me....right after he blew up the engine. So I need to source a fresh S65 4.0L V8 or rebuild the current S65. It's stashed at a friend's shop for now but should be removing the engine after SEMA to assess the damage. It's a nice car, I always wanted to buy a e92 M3 so it's a dream come true to basically get one for free. I'll post a few pictures here as it comes along. My buddy put on an aftermarket exhaust and wheels already and now he's talking about a supercharger. I'm going to need a bigger garage

 

[gtxracer2]

Installed two brand new radiator fans last night and discovered only 2 screws securing the front bumper, which is yellow underneath the black cheap-spray. I'll be cleaning up the little bits and pieces now that I've discovered all this. I think I'll be upgrading the shifter soon, I really can't stand how cheap it feels. I'd rather sit in these wrecked seats than shift with this this flexible factory shift knob. I can feel it move when trying to get into gear. I'm also looking at just shimming the OEM 996 shifter and adding metal bushings for the time being.

Couple more items that need attention:

• Cowl plastic trim needs replaced, mounting locations are broken
• Cowl seal is worn out too
• Roof rack tabs are out of place, need new hinges
• Missing front bumper hardware - screws and plastic clips
• 3 lug bolts are different, need to order replacements
• P car dash Tach and oil pressure gauge aren't working/hooked up
• Headlights only work well in high beam
• Adjustable steering wheel column doesn't hold position, needs tweaked
• Car needs ~450 miles put on it to break in new crank and rod bearings
• Missing hardware in frunk area, plastic caps, bolts, pins, etc.
• Other little odds and ends need hardware/fix/straightening

Looks like I'll be placing orders with Suncoast and Pelican to get most of these parts. Still deciding if I want to go with used Recaros or new Braum seats...

 

[Roc Doc]

losing or damaging the front plastic bumper trim / air dam, calling it a splitter is generous, on a 997, or the 991.1 and .2 Cup cars is something easily felt by the driver (car definitely exhibits more understeer). We used to carry half a dozen spares and treat them as consumables.

There is a company that makes fancy carbon versions for the street posers, who usually rub them against the curb or parking stops. If I remember they ran almost 1K compared to the $200 odd for the OEM plastic version. I would also consider adding vertical fences at the front edge of the front wheel wells to generate more downforce, should be able to get them through Porsche motorsports as they were OEM on the Cup cars. You can also trim the fender liners to encourage the air to exit the front wheel wells, and reduce lift. Make sure the OEM floor panels and covers are servicable, known source of dirty air.

I would tame the rear end for track days through rear toe - in, and rake. The whale tail / duck tails, while looking cool definitely move the aero center of pressure rearwards over 85 mph, and change the balance of the car substantially especially through high speed (90 mph plus) turns. If you do choose to add any rear wing, you are going to need to add a ton of rake to dial out the understeer / push. Likely not noticeable on the street, or even street tires, definitely a concern on the track. Glad you made it over here, enjoy this thread.



The Katz Race Car AeroD book is pretty much industry standard - but don't waste your time and try to re-invent the wheel (or in this case wing) either, the engineers at Porsche really do know their stuff. If you want to see wild and wacky aero, most of which is useless just visit a PCA event. Decent driver in a stock car will still be quicker than most drivers with several tens of thousands of $$ who have every carbon appendage you could imagine.

But I prefer a sleeper look anyway.

My car was a 76, that I added Carrera flares and the Carrera lower valance and spoiler when I did the 3.2l swap and even with my limited HP and track time, it made the front end stick much better and easier to rotate the rear. Carl Young advised me not to do a rear spoiler, he said when they put a wing on his Silver State 914 (before they ran the 993 TT), they lost 15mph at the top end.

 

[gtxracer2]

Last night I removed the center console to adjust the shifter and noticed the bushings in the OEM 996 shifter are metal already. Cool! Still sloppy as hell though I adjusted the cables and I think 2nd gear will hold better now. I also have the 2nd gear detent upgrade which I'll install soon.

I cleaned up a few other items last night too:

• Glued steering wheel carbon fiber insert, it was loose
• Glued shift pattern trim piece back in place on the shifter
• Used heat and WD-40 to break loose the telescoping column lock that was stuck

Don't mind my shop crocs

 

[gtxracer2]

I found a local guy that has Mk1 996 GT3 side skirts that he will trade for my OEM mufflers. So it looks like this car will be converted to a GT3 appearance. The rear bumper is the same, and I have two of them, so I'll spray both of those when the car is painted. I still need to find a MK1 GT3 or Aero front bumper. Hoping to find an OEM unit as fiberglass is never as good. I am also looking at Alcantara steering wheels to closely match the GT3 look and maybe some sportier bucket seats from Recaro. It'll still be green, like this, but with the GT3 RS wing:

GT3 RS:

This is a GT3 clone. I really dig the sound, it's apparently a supercharged M96 but sounds similar to my car. Maybe I'll kick my redline to 8k in my LS1 and just pray those stock rod bolts were torqued down on a Tuesday and not a Friday. I dig the TE37 Volk wheels on this car and I really like the yellow paint scheme. I'm thinking rainforest green GT3 clone with GT3 RS wing and bronze TE37s for the final look of the car.

I also ordered a custom wood grain shift knob to replace this rubber OEM garbage. I'm holding off on the Numeric shifter until I correct a few more issues. I ordered a new cowl trim piece, front bumper screws, plastic rivets, and a oil pressure sensor. I also have the final trim piece for the HVAC controls in route. I'm reworking and tidying up the engine bay wiring for the final time while I install a Radium Engineering catch can: Universal Single Catch Can

Small upgrades and fixes, but they'll make a big difference in overall experience and feel to the car.

 

[budget76]

Now you're in the fun stage, driving it and updating/improving as you find the needs

 

[gtxracer2]

Now you're in the fun stage, driving it and updating/improving as you find the needs

Yes and crossing fingers I don't blow up another LS1 :D

Small leak at the oil pan to rear cover interface. Looks like I'll be pulling the headers and pan sometime this winter! Probably a Christmas wrenching project.