Something isn't right here. C43 motors have higher CR than 430 engines.
That means different pistons.
Heads, that's news about massaged ports.
The 3 valve motor don't make power like; even a new Mustang GT. If your minds set on your CLK do a hybrid. Keep your block, have it rebored. Put in
aftermarket 55 pistons, massage the heads, get your 430 cams reground, put 55 aftermarket pistons in that thing. I'd put that setup against a 55
Sorry for the delay in responding, I don’t visit this forum that often.
You’re right, something isn’t right, but no one has been able to assuredly solve mystery. I have (what I think is) a pretty good guess, but it’s just a guess, and it’s been shot down before. According to AMG, the compression ratio on a C43 is 11:1. According to MB USA, the compression ratio on a standard 430 is 10:1. Looking at the part numbers for C43, the pistons, rods, heads and crank are the exact same as a standard 430. How they manage to use those parts and increase compression by a full point is the mystery. The July 1998 STAR magazine has a C43 article by Frank Barrett. Per the article, the engine received what he called "breathing improvements". The article states the intake manifold (which uses the same part number as a standard 430) has what he called "bigger ports". I would guess he meant the C43 TB, which was larger than a standard ME 2.0 TB, but he wrote ports
- plural. It also says the air cleaner is a low restriction box, the cams have more duration, the valve springs are stiffer, it has a unique oil pump and it has a low restriction exhaust (although since it’s the only W202 V8 exhaust available, I don’t know what it’s lower than).
My "guess" is the heads were milled. Although a full point means a lot of material came off the heads. A whole lot. However, when heads are milled and a lot of material is removed on domestics, the intake side of the head is machined so an intake manifold with stock dimensions will fit. The point being that it's obvious. With that much material removed, the new cams "may" be required to have less lift, although I’ve never seen C43 cam specs.
Now the argument against this guess work - I’ve been told by a trusted source that the roof on the exhaust ports has been cleaned up. Just the roof. This same person told me the floor and sides were exactly the same as a standard 430, and if opened up, low RPM velocity would fall through the floor, making the engine a lot more peaky than I would like. He also said the heads haven’t been milled, the intake side of the heads haven't been touched and if the CR is a point higher, then AMG used different pistons. After showing him the part numbers and checking for himself, he said either the MB USA parts database is wrong, or the motor doesn’t have an 11:1 compression ratio – hence my saying no one has been able to assuredly solve mystery. Before writing off the MB parts database error, try looking for a 1131410124. It doesn’t exist. That was an OE TB for a 55. Look for a C43 piston, you'll see 1120300617.
Lastly, this dyno sheet is from a bone stock, 9,000 mile 2002 CLK430. Based on the dyno numbers, 302HP really isn't that far off.
Philly, have you considered swapping in a 5 liter M113? They have a lot more torque than a 430, though not as much as a 55.