Hi guys,

I am considering a C55 or a W204 C63 in the near future.

Ive always loved the W203 body style compared to the W204. Also the C55, I believe, has a reputation of being very reliable, along with all of the old SOHC mercedes engines. Only issue is that its a but underpowered compared to todays latest offerings.

So I would likely be modding the C55 if I were to purchase 1. Can somebody tell me whats the most horsepower a NA C55 has achieved and with what mods?

280rwhp stock
ECU - 10
Intake - 5
Headers - 10
Exhaust - 0~5?

Seems like I would only reach about 310rwhp but I think i read about several C55s NA tuned that achieved around 340rwhp. Is this possible?

If you are used to modding cars with ease the C55 is not the vehicle for you.
I've been modifying cars for performance (not that stick-on body and flashy garbage) since the mid 1980s. My C55 came along in October as a new daily driver. The bug is biting me hard and I'm itching to get some power out of this thing. So far, the mods are limited to a tune and shorties. Mild exhaust mods are likely next.

The mod that keeps running through my mind is dropping a 113K in the car. The temptation is really hard to fight. My problem is that I find it very difficult to justify dropping that kind of time and money in a daily beater when I have so many other things to be doing. That engine swap is NOT for the timid or cash-strapped person.

In reality, I need to quit spending money on this thing and get my Imperial back on the road so I can build the roadster of my dreams.

Logic dictates driving it as-is.
Emotion says do the swap.
Brain says ditch the car for a low performance model in order to remove the temptation and get on with life.

Buy the C63 and get an engine tune

Search "Swedepat" and you will get some answers.
I think he got 367 wheel-hp out of his n/a engine, or more.
Ported and polished heads among a lot of other goodies. Very rough casting in heads, much can be done there.