E9 s38b36 conversion

[DIESEL1]

[FONT=Arial, Helvetica, sans-serif]Hello to all,

Before I begin, just want to thank all on this forum for making time to write about their experiences with certain repairs, upgrades and modifications on their ever so delicate coupes. I am currently involved with a 1971 2800CS E9 S38B36 swap and have few questions for those who are kind enough to share their experiences with this conversion.

I am starting with a 91 M5 and a 1985 535i as donor cars. Using the S38B36 from the E34 M5 and the Getrag 265 from theE28 85 535i and if need be several other parts. The S38 Is fitted on the original 2800CS engine cross member using the original engine mounts and brackets from the coupe. Unlike other swaps by other members, I did not nor did it seem I had to remove the blocks on the frame rails on which the cross member bolts to.

I am having an issue with the hood shutting as the inner hood reinforcement rod is hitting the fuel rail of the S38. Do I need to drop the engine cradle a bit by means of shimming? or do I need to use different motor mounts and brackets? or simply cut off the rod. I'm concerned about lowering the cross-member as that places the oil pan closer to the ground. I used the E28 535I center tie rod link as the original one from the coupe did not clear the S38B36 oil pan. The oil pan is also in the way of the sway bar. Have to figure something else for that. Read on this forum where someone used the oil pan and the oil pump from a 79 528i to solve the clearance issues with the sway bar.(is this the only route?).

In order for the rather large S38B36 intake plenum to fit I will be installing a hydro boost brake set up from a 79 BMW E23 733I which some prefer over the E28 535I hydro boost as the later is longer by and inch or two. Converting to a 1974 2002 tii booster as few have suggested is not working for me.
I will be adapting to use the bigger diff and boxed trailing arms from the 535i. The original C channel built E9 trailing arms seem too flimsy to me to handle the extra torque of the S38(of course the body will be reinforced as well).

Must I use an electric fan for cooling? I prefer to retain the fan blade and clutch set up for cooling. To achieve this do I need to move the radiator support forward? Which BMW radiator should I use? Any engine oil cooler placement and fitment suggestions? Any AC upgrade suggestions as my coupe was not equipped with AC? Where is the best place to house the S38B36 engine computer?

Please feel free to comment, correct or criticize me.

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[rb1971]

Howdy and welcome. I originally responded in the other thread.

I am starting with a 91 M5 and a 1985 535i as donor cars. Using the S38B36 from the E34 M5 and the Getrag 265 from theE28 85 535i and if need be several other parts.

Great swap! Make sure you reinforce the frame of the car or you risk serious body flex from the much higher than usual horsepower. There are a number of threads on this, and coupeking's website shows some of the reinforcements the factory racing teams used back in the day.

I am having an issue with the hood shutting as the inner hood reinforcement rod is hitting the fuel rail of the S38. Do I need to drop the engine cradle a bit by means of shimming? or do I need to use different motor mounts and brackets? or simply cut off the rod.

I had the same problem, and removed the hood support. Right now I'm kind of puzzling over it, but it certainly won't end up being the same system that most CS/CSi's run. (Right now, I run with a race hood prop in the trunk for emergencies.)

I'm concerned about lowering the cross-member as that places the oil pan closer to the ground. I used the E28 535I center tie rod link as the original one from the coupe did not clear the S38B36 oil pan. The oil pan is also in the way of the sway bar. Have to figure something else for that. Read on this forum where someone used the oil pan and the oil pump from a 79 528i to solve the clearance issues with the sway bar.(is this the only route?).

I've heard this before but we didn't have that particular problem . Did you upgrade the engine mounts?

In order for the rather large S38B36 intake plenum to fit I will be installing a hydro boost brake set up from a 79 BMW E23 733I which some prefer over the E28 535I hydro boost as the later is longer by and inch or two. Converting to a 1974 2002 tii booster as few have suggested is not working for me.

Hydro boost from the M1 also fits and is surprisingly not that expensive!

I will be adapting to use the bigger diff and boxed trailing arms from the 535i. The original C channel built E9 trailing arms seem too flimsy to me to handle the extra torque of the S38(of course the body will be reinforced as well).

I used an original 3.45LSD and haven't had any problems yet. I thought of going your way and decided since there have been cars running 500+hp on side loaders upgrading was not necessary. But that's not a knock against your proposed approach.

Must I use an electric fan for cooling? I prefer to retain the fan blade and clutch set up for cooling. To achieve this do I need to move the radiator support forward? Which BMW radiator should I use? Any engine oil cooler placement and fitment suggestions? Any AC upgrade suggestions as my coupe was not equipped with AC?

This is a big question. Since these cars are all just a little different, you might have enough room to go with the mechanical fan. We had enough room, but then decided to switch to a modern style radiator, which led like falling dominoes to an electrically switched fan. There were some minor modifications that had to be made to the supports, which will be obvious when you get there.


Re AC, your toughest job will be to source the parts that go inside the car. We had to get a blower from Portugal! Once you have everything inside the cabin, there are a number of options. My approach was to use modern parts in front of the firewall, and the 5-series compressor that works with the S38.

Where is the best place to house the S38B36 engine computer?

How much of a restore are you doing? Lots of folks go glovebox, we went inside the heat shielding in the passenger floorboard (in a protective box).