Engine conversion/rebuild dilema

[Gary Waggoner]

I am starting from scratch with this since my car is a 2800CS. In lieu of the values of these cars being all over the board I am wondering about my choices of engine swaps. I own a 1992 M5 with an S38 that needs nothing and would want to source a good 265 transmission to go behind it.....or should I find a 3.5/265 and build it to my needs. I would like to end up with 275hp+. My M5 is a complete car that I don't have much $ invested into, so it would be easy for me to disassemble it for the drivetrain. On the other hand I have been quoted 10k+ for a complete fresh hi-po version of a 3.5, but still would have to purchase the 265 transmission. Which direction makes sense as far as cool factor, resale or value changes? What do you think would be most desirable?
Gary

 

[teahead]

S38 would be the ticket, but is your M5 basically a parts car?

 

[Gary Waggoner]

Its a running and driving car, but the s34 chassis are not worth that much. The engine is its only value.

 

[Wladek]

Its a running and driving car, but the s34 chassis are not worth that much. The engine is its only value.

Save E34 M5 it's a good, valuable car (it will rise in value). In Europe prices for the nice pieces are around 20k EUR for S38B36 and 25-30k EUR for S38B38.
Better find M30B35 & Getrag 265/6.

 

[teahead]

If that's the case (I kinda of like E34s), then part-out that M5 for its awesome S38B38 and find a 265 for it. Sounds like you need a 265 anyways, regardless of engine.

275hp from an M30...will be trickly w/o turbocharging, and will probably cost you about $6-8k to get it built (new high comp pistons, cam, etc.). You already have a motor (lucky dog), so might as well use it. Will be a little more tricky to install, but has been done many times.

 

[autokunst]

Not knowing anything about the shape of the M5, it seems a shame to sacrifice a nice e34. My vote would be to build a 3.5L to power your e9. It would be more at home in there.

 

[Gary Waggoner]

My M5 is not that nice. I bought it only for the drivetrain, so I have no problem parting it out. It can be sold for easily enough to pay for a 3.5 conversion and transmission, and I have a soft spot for the M motors. I have one in my 74 2002.

 

[teahead]

Not knowing anything about the shape of the M5, it seems a shame to sacrifice a nice e34. My vote would be to build a 3.5L to power your e9. It would be more at home in there.

Looks right at home to me:

 

[teahead]

If you don't want to use the S38, let me know, I know someone (myself) that would take it off your hands.

 

[Ohmess]

I too like the e34; I am taking care of my son's right now for him.

I believe Korman moved the firewall in Doug Dolan's car in order to get an S38 into his car. Food for thought on that part of it.

And while it looks really cool, I think that engine is overkill for the e9 chassis. Your differential mount would need to be reinforced, as would your rear shock towers. You likely would be unhappy with the stock seats; anytime you nail it in a corner you would be sliding around on the stock seats. And still the chassis has a lot of flex in it for that much power, and like all the motorsport engines, the S38 really comes into its own when you get high in the rev range. It can be tough to find places to spend a lot of time high in the rev range of that engine on the streets. Most folks here have gone for a big valve M30b35, emphasizing torque in the ranges they use most often.

 

[Markos]

I think the S38 and the e34 M5 are both very cool. An S38 in an e9 doesn’t do it for me. If you ran open trumpets without an air box I could be convinced otherwise. Also, I know it is counterproductive but an s38 running DCOE 45’s would be pretty awesome!

 

[HB Chris]

Gary,

Be sure you speak with owners who have experience with the options you are considering. A nice b35 or m90 stroker motor are both great options.

 

[sfdon]

I think there are 5 engines that are easy and make sense.
Not the m5 Engine.
Maybe 3.5, cam, high compression , ITB ?

 

[Wladek]

Consider a purchase of E23 745i as a part car for the engine.

 

[sfdon]

I’m firing up a ‘85 745i turbo Engine in a ‘74 coupe using 2017 MSPNP2 this weekend.
Challenging.

 

[Gary Waggoner]

I think there are 5 engines that are easy and make sense.
Not the m5 Engine.
Maybe 3.5, cam, high compression , ITB ?

What are the difficulties in using/installing the M5 engine? I figured it would bolt in mechanically, electrical and plumbing are easy for me as well.

 

[Ohmess]

You won't find a lot of e9s with M5 engines in them. I've only seen 2, but I see one of them regularly as Doug lives nearby. I am pretty sure, as I posted above, that bolt in is not possible. Ray Korman had to modify Doug's firewall. Also, the battery was relocated and the tray removed, and the hood opening mechanism was removed. I think Korman is still active with his shop; you could potentially contact him about this. He's the only person I know who has actually done this.

 

[aearch]

i have done it on 4310316 begins
it is a bolt in with a few minor things
my firewall i dimpled 1" at the corner --only for installlation purpose as it sits 1" away installed

 

[Gary Waggoner]

I think the S38 and the e34 M5 are both very cool. An S38 in an e9 doesn’t do it for me. If you ran open trumpets without an air box I could be convinced otherwise. Also, I know it is counterproductive but an s38 running DCOE 45’s would be pretty awesome!

Love that.

 

[sfdon]

Its a bunch of work.
Hydroboost brakes to start.
And then you have to drive a car that was never meant to have that engine.
which means you have to drive a high reving car thats 50 years old.
Its annoying.