The E31 850i (6MT) Project begins. Dyno, Exhaust, and more!

12-02-2025

This is a 1991 E31 850i with just under 150k Kilometers on it. 6MT and LSD as god intended.

The engine has to come out because of a leaky rear main seal, and we are planning to build a custom catback/valved equal length stainless steel exhaust for it and possibly doing some headwork for additional flow and power.

So I decided to dyno it to get a baseline!

An image attached to this post, provided by the poster

Related threads I previously posted:

Post purchase:

https://g80.bimmerpost.com/forums/showthread.php?t=2203013

Replacing the rusty mufflers:

https://g80.bimmerpost.com/forums/showthread.php?t=2215434

PS:

The entirety of the exhaust system will be done by Fusion Motorsport Fabrication, located at Pickering, Toronto.

https://fusionmotorfab.com/

They also just recently finished the absolutely stunning custom catback/valved titanium exhaust for my E92 M3 which you can follow here:

https://www.m3post.com/forums/showthread.php?t=2210028

An image attached to this post, provided by the poster

12-03-2025

Used to own one. Fun car. Subscribed.

12-03-2025

Love it. Fun times.

12-03-2025

Nice don’t see enough of these

12-03-2025

WoW! 2x the cylinders of an E28 M5,...E36 M3,...E46 M3,...335i,...535i (F10 / 3x more than 528i F10), and less power than every F30,...G20, G30 and it barely makes 212Hp! Yet! The 5.0L V10 in the E60 easily makes 500+ Hp! Clearly, the price of the V12 850 was based on 1) Styling and 2) number of units built!

Edit: Lovely car though!

12-03-2025

JMD wrote
WoW! 2x the cylinders of an E28 M5,...E36 M3,...E46 M3,...335i,...535i (F10 / 3x more than 528i F10), and less power than every F30,...G20, G30 and it barely makes 212Hp! Yet! The 5.0L V10 in the E60 easily makes 500+ Hp! Clearly, the price of the V12 850 was based on 1) Styling and 2) number of units built!

Edit: Lovely car though!

The e31 850csi came out in 1992 and was rated at 381hp. The e60 m5 came out in 2005 and was rated at 507hp. Engine technology improved a lot in those 13 years.

12-03-2025

Such a beautiful car....

12-03-2025

Love it. Looking forward to the build.

12-03-2025

Absolutely stunning! Please keep this updated as you progress :thumbsup:

12-03-2025

Subb’d!!

12-04-2025

What a beauty. That body style is just flat out timeless. Bring back straight lines!

12-04-2025

You guys wouldn't happen to know where I can find a pair of Schrick cams for the M70, would ya? I've been looking and I can't seem to find any.

Schrick item number: 0239L1641-00 / 0239R1641-00

After we do all the headwork, that'll be the last piece holding us back.

12-04-2025

https://www.gladen-motorsport.de/en/BMW+M70+SCHRICK+Camshafts+264-.htm

Probably made to order at this point...

12-04-2025

Always have loved these cars, looking forward to the updates. Thanks

12-06-2025

Love these cars, I regret selling mine.

12-19-2025

I have some potentially good news. We've been talking to Schrick and the only way we can get a set of new cams, is to order at least 10 sets. That's the minimum order quantity.

Essentially, we have to do a group buy which is why I need to ask if anyone is interested in a set of Schrick cams for the M70 engine. Given that they are quite unobtanium on the web at this moment, it would be a good opportunity to get a set.

Schrick item number: 0239L1641-00 / 0239R1641-00

Let me know folks!

12-20-2025

Maybe contact M539 restorations - Sreten may be interested

12-20-2025

Tambohamilton wrote
Maybe contact M539 restorations - Sreten may be interested

Just did.

12-21-2025

Unrelated, but we are done with the E92's exhaust.

https://www.m3post.com/forums/showthread.php?t=2210028

12-22-2025

Exhaust looks great. Bimmerworld did dyno testing years ago that showed moving the X forward to where the pipes narrower after the transmission yielded a measurable increase in torque.

02-11-2026

The engine and trans are coming out soon, and we have on hand all the gaskets and seals that we need to refresh the engine.

Since the cams and pistons I was originally planning to use are unavailable, we have decided the best route to make additional power (and noise) is to supercharge it. It's not set in stone yet but it seems the logical choice given the low compression nature of M70.