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Thread: Hi, '90 735i getting GM LSx swap

  1. #1
    Join Date
    Mar 2017
    Location
    Salt Lake City, UT
    Posts
    3
    My Cars
    '90 735i

    Hi, '90 735i getting GM LSx swap

    Hello all,
    I have a 1990 7351 with 350,000 miles on it, It's a clean navy 4-door with a tan interior getting dyed grey, the factory audio has been replaced and sounds fine, I just replaced some bushings in the front suspension, fitted new tires, 215/60R15s front and 215/65R15s rear, replaced the accessory belts, and chased an overheating problem.
    It needs the valve lash adjusted, MPG averages upper teens at best, power is relatively good but it won't jump away from a dead stop. Shouldn't this thing have a 3.91:1 gear in a 188 mm rear diff? It does have a functioning Limited Slip.
    I have an iron-block 2001 4.8L version of GM's LSx V8, with a custom oilpan, 2 different intake manifolds, a pair of '99 Z28 exhaust manifolds, and I have a '98-ish 4L80E to go with it. It just needs a looser torque converter, the one it has is from a 7.4L work truck. But I'd prefer a built 4L60E.
    Eventually I'll do an E-Rod LS3 swap, and a Ford 8.8" swap. Long before then, I'll be looking to trade these 3.91 gears for something closer to 3.0:1, I know the choices in a 188 include 2.93, 3.07, 3.15, 3.23, 3.25, et cetera.
    This is a grand touring build, comfy relaxed cruising and fun in the mountains. This is not an autocross, road-race, dragstrip build, nor a grandma build. A/C must work. And cruise control. p/s, p/b, emissions-legal, 30 MPG. But it must shred both rear tires, without holding the brakes, when flooring it from a dead stop. And it must do so without the annoyance of a too-loose torque converter.
    This will end up a show-quality swap, and it must end up 300,000-mile reliable. Drivetrain aside, exhaust aside, cooling aside, the budget for the swap details, like mounting, linkages, adapters, etc. is $1,000.00, just to keep it realistic. This means using mild steel rather than billet aluminum, for example.
    Vorshlag? Inspiring, but they don't support the E32, and I can do better at far less cost.

  2. #2
    Join Date
    Jul 2016
    Location
    Chicago, Illinois
    Posts
    3,842
    My Cars
    are slow
    Is that you, 734i? Nice choice with the longer gears and smoothness of an LS.

    The E34 related LS1 builds should help you out a lot.
    Last edited by XAlt; 03-18-2017 at 06:43 PM.

  3. #3
    Join Date
    Jul 2016
    Location
    Chicago, Illinois
    Posts
    3,842
    My Cars
    are slow
    Here's one of the later builds. I assume the 735's trans tunnel can cram in a 4L80E, considering that people have hacked them onto E36s.

    https://www.bimmerforums.com/forum/s...p-build-thread

    This is on the Big Six E34 subframe, the harder of the two to swap, and identical to your 735's. Hopefully the bigger space of the E32's bay will allow for clearance and require less relocation.
    Last edited by XAlt; 03-19-2017 at 12:26 PM.

  4. #4
    Join Date
    Mar 2017
    Location
    Salt Lake City, UT
    Posts
    3
    My Cars
    '90 735i
    Yeah, I was 734i, Hi. Life happened. I'm now working at an automotive machine shop with a dyno and a flowbench. I'm the cylinder heads guy, but I also do blocks, rods, and I'm learning the dyno. Anyway,
    Thanks for the link, good info in there.
    I'm thinking about front-steer with a rack, maybe a modified Mustang II-style IFS swap. Heidt's makes the best ones, but Speedway Motors has the best prices. Makes a big brake upgrade cheap and easy. Also simplifies LS mounting.
    Here's a link to an RX-7 I did a few years ago: http://www.rx7club.com/build-threads...-more-1072610/

  5. #5
    Join Date
    Jul 2016
    Location
    Chicago, Illinois
    Posts
    3,842
    My Cars
    are slow
    Pretty neat swap with the RX.

    A rack on an E32 would be quite neat, as with the BBK.

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