If I somehow found a source for reasonable pistons and conrods and did a valvetrain rebuild, how much power could i make from a tuned (NA) m103? realistically, say $2k without labor. If anyone has built up an m103 motor without a turbo let me know(excludes superchargers too).

 

Not enough to spend $2K on.....
$/HP on a NA M103-12V is not cost effective.

 

i agree $2k isn't enough but ya its possible to do so if you do make a high compression m103 post it

 

RENNTech charged $15k for their 3.6L stage 2 engine mods yielding 260hp. They either made a hefty profit or there was a huge amount of skilled labor involved...

 

Compression alone is not worth the cost of the pistons and labor..
If a performance cam was still commercially available then you could build an engine similar to what AMG did with the 3.2L.

The 3.2L AMG had the CR increased from 9.2 to 10:1.
The engine was bored and stroked and the heads ported and polished.
An AMG long duration cam was used with a performance exhaust system.
It produced 245HP and 239 Torque on a Euro spec engine.

 

Here's a short break down from two engine builder's quotes a couple of years ago:

• Custom rods, hard to find crank, late M104 block ~ $3.5k
• Machine shop costs, misc parts, many hours port/polish the head - not quoted

• New aftermarket pistons (not Kobbleschmidt) and con-rods ~$2.5K
• Machine shop costs, bored .060 over and steel sleeved, many hours of cleaning up casting issues ~$2.5k

If you're skilled at engine assembly, head work, and know which parts to buy you can probably do it within a budget...

 

As it's been suggested before, the Germans did their job when pulling power from these motors. You'd be better off to turbo or supercharge the 104 3.2 engine. The 103 does not lend itself well to supercharging because of the design, but it's a natural for turbo. I'm going to do mine with the guy in Seattle that posts here. Eventually, if I don't wreck the wagon, I'll be looking for a tight 3.2 to supercharge.

What is your objection to turbo on the 3.0? I don't think you're going to get better bang for your buck.

Kevin