2003 325Ci 'vert getting LS3 +T56 turn key project

SiBriers said:

A man with a plan!
Sounds awesome.

Looking forward to your updates - wish we could source motors and trans like that for reasonable money here in the UK.

Would love a setup like that in my 325ci but parts alone would probably be close to M3 money..

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Oh, it's not that cheap here in the 'states either... By the time I'm done, I could have gotten an M3, and most likely have most of the major 'new to me' replacement/upkeep items done. I'm already in for nearly $20K USD, but I'm pretty meticulous in how I do things: All the maintenance items on the car have been gone through: bushings and suspension, the convertible top/hydraulics/top wire harness, all the existing electronics and normal 'wear' items.

The donor drivetrain has 38K miles, and while it's out, it'll be getting a comp cam + valve springs + valve pushrods + LS7 rockers (I don't want to pull the engine back out to do any of it later). Short shifter on the T56.

I'll never get my money back out of it, but that really isn't the point (I already have a corvette https://drive.google.com/file/d/1puQy_EjNMPPgx6dmGSoy7x_fNfO1SbVX/view?usp=sharing and highly modified F150 truck https://youtu.be/-4xEF602jKI ).

I'm not a big fan of the Japanese 'tuner' scene or modern muscle cars (but something from CR Coachworks [ https://www.crcoachworks.com/ ] would be awesome if I could afford it ).

This lets me keep a e46 (I've owned one since it was the current model), and get the 'vette torque (target goal is 450 crank HP, and 450 crank TQ), all while having a car that can be the permanent 'project' to tinker with on a platform I've owned for 20 years already... (I am quite familiar with just about everything that can go wrong on one of these cars - no surprises left!)

Dan B

While you are working on the valve train you may want to consider Straub trunnions and bushings, there is a lot of talk about them over at www.ls1tech.com

I am working on a very similar project, currently working the transmission tunnel to fit a 4L60E behind a 5.3 LS on a 2003 330ci.

I used the TDR (Tire Death Racing) engine mounts from www.v8schassis.com I am very impressed with the quality of the mounts.

Using the automatic trans is a bit out of the ordinary for a E46 LS swap, but it makes for an easier swap into an already automatic car and I already have a peppy 6 speed ND Miata in my stable.

I will have to modify some headers or exhaust manifold to work with the transmission and go around the pan. the swap headers are all made for the T56 and are very expensive compared to modifying a pair of block huggers, but that will certainly take some work.

I read you are going to use the BMW exhaust, will it be too restrictive? Are you using everything from the flanges back, including the cats? If it works I can do the same thing and save myself some time money and effort.

damon forrer said:

While you are working on the valve train you may want to consider Straub trunnions and bushings, there is a lot of talk about them over at www.ls1tech.com

I am working on a very similar project, currently working the transmission tunnel to fit a 4L60E behind a 5.3 LS on a 2003 330ci.

I used the TDR (Tire Death Racing) engine mounts from www.v8schassis.com I am very impressed with the quality of the mounts.

Using the automatic trans is a bit out of the ordinary for a E46 LS swap, but it makes for an easier swap into an already automatic car and I already have a peppy 6 speed ND Miata in my stable.

I will have to modify some headers or exhaust manifold to work with the transmission and go around the pan. the swap headers are all made for the T56 and are very expensive compared to modifying a pair of block huggers, but that will certainly take some work.

I read you are going to use the BMW exhaust, will it be too restrictive? Are you using everything from the flanges back, including the cats? If it works I can do the same thing and save myself some time money and effort.

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I don't plan on beating on the car (at least, not initially). 3 or 4 years out, the engine will come out, be completely gone through. That'll give me time to get the M3 rear end in it, sort that out completely, get some better sway bars and other bits on it, get the interior replaced, get it painted, get wider rims/tires. The 'performance goodies' will all go in at the time of the engine refresh (FAST intake, 102MM throttle body, ported heads - the 'usual'), but I have to have the M3 rear end (or a Ford 8.8) before I try and do silly HP/TQ numbers...

Zero2Sixty Performance will likely fab mounts for the engine/transmission. Those items are not on the itemized list of parts in the estimate, but fab costs are. He's done this a couple times (twice on his own e46's), and I suspect that it will let him adjust things to his liking if he simply builds them.

I also have a '00 323Ci with a ZF auto, and will eventually swap it as well (one swap/project at a time). I'm interested to know how much 'massaging' is required for the transmission tunnel, as I'd really like to stick a 6 speed auto in that will accept input from the paddle shifters I've grafted onto the existing 5HP19 ZF. As I understand it, all the electronic 6 speeds are big, so it'll be more involved in terms of chassis modification than a T56.

Even if tying into the stock exhaust is restrictive, it'll keep the initial cost down, and give me another thing to 'tinker' with at a later date. A stock LS3 makes 430HP; Even if the engine 'only' makes that with the cam in it, that's plenty to play with, and if opening the exhaust up later yields 20 or so HP, and some additional TQ, then I won't feel like the new exhaust was for nothing.

It' a long term project for me: something I can play with (since the corvette is still under warranty, and I don't want to do things to it to impact that).

Dan B

Another Update on the project.

To put down bigger HP numbers, the car needed some wider tires, and therefore wider rims.
I picked up some replica 437M wheels in 18x8.5, and am planning on some Michelin Pilot Sport 4S's in 235 width.

Dan B

Minor update on the swap/build:

I picked up the necessary bits from Morimoto for a HID retrofit. I've got a couple of these cars, and have spare headlight assemblies from a previous HID conversion (last time ['00 323Ci], I purchased a pre-built assembly, and swapped in the entire unit, so I've got a spare set already). While waiting on the driveline swap, I'll restore and build out the previously swapped assembly, and then install/wire in the '03 325Ci when the car comes home. This thread (@fat-marshmellow: thanks for posting that! quite useful!) is my motiviation and guide.




I also purchased the tires for the rims: a set of Michelin Pilot Sport 4s's in 235x40x18 (no-pics <shrugs> - it's a set of tires). The sizing is based on everything I've read, and also the clearances on my '00 323Ci 'vert (running 225x40x18 on the same width rims, and wanting to run 'square' instead of staggered - the front is tight on clearance, but the rear could most likely go 245 width).

I am super-excited about getting the car back - like a kid at Christmas that knows something good is waiting for them. I keep piling up parts in my living room for 'after the engine swap'.

Dan B

Well... It didn't take me long to get the next phase lined up.... A M3 rear end swap...


A bushing set is in route, the diff will be sent out for a full rebuild, and the trailing arms and diff carrier will be sent off for powdercoating before installing...


Dan B

Update on the swap:

LS3 is in the car! Much remains for the shop to do, but it now 'feels' like it's moving along better...

Dan B

Update on the M3 rear end... Powdercoating done!

It'll go back together in the next week or two, and get slid under the car once the LS swap to the stock open diff is completed. (The 4-bolt driveshaft is already built... Might as well run the 'engine swap' part of the project all the way to completion before embarking on the rear end swap.)





Dan B

Another Update on the driveline: The trailing arms powdercoating is done!



Time to get it all back together!

Dan B

Not a major update this time, but some of the 'fluff' for when the car comes home...

Hubcaps, hood, and trunk emblems subtly modified...



Dan B