Dear All,
My W111 Coupe 5.0 V8 is close to completion so it is now time to think about my next project, which will be a Pagoda V8 with manual transmission. My objective is obviously a fast car, but one which is nice and easy to drive, homogenous and balanced and that remains a Mercedes.
Here is what I have gathered so far: I was lucky to buy a ’71 280SL at an auction. The car needs work, but is very sound rust-wise (former Texas car). I also got a low miles 5.6 M117 engine out of a totaled 560SL, and a very rare AMG bellhousing to fit a Getrag 265 with that engine. I also secured the Getrag 265 transmission, and I also have a 3.27 and a 2.85 rear end.
My experience with the 5.0 W111 Coupe project will help me a lot for this one. Below is a list of what I intend to do:
1: More power. My plan is to keep the 5.6 long block stock for now. This US 5.6 is a 9:1 CR and camshafts are the same as the euro 9:1 CR. So my idea is to fit an early K-jet and ignition system I have out of a euro 5.0. This will get rid of all electronics and will allow to play with ignition advance by rotating the dizzy. I also want to get dual exhaust line ala 6.3. I believe I will be able to get a safe 275hp @ 5500 with a good 40 kg of torque around 3500 rpm. This is more or less what euro 9:1 5.6s deliver and the difference with the US version is that US engines are chocked at the exhaust and ignition curves may be a bit different. Mated to the Getrag 265 and a 2.85 rear end, this would make for a very pleasant driving I believe. I have a 3.27 on my Coupe and the manual transmission ratios are similar to the Getrag 265. This is OK because torque and power are delivered at higher rpm.
2: Overdrive: 5th on the Getrag 265 is .81. This would be around 2400 rpm @ 80mph with a 2.85 rear end. It is equivalent to a 2.31 rear end in fourth. By comparison 500SECs had 2.24 rear ends.
3: Simplicity and reliability. I guess the early K-jet I want to fit is among the simplest systems, still with no electronics. Ignition will be the 500 hall effect one which is trouble free.
4: Improved handling: I’m planning to adjust the rear suspension so as to have a bit of negative camber when the car sits still. I’m also considering fitting poly-bushings like the ones I have on my Coupe. I’m globally very pleased by how sharp they make the car handle, especially at higher speed. Unfortunately they transmit vibrations at low speed on degraded surfaces, which is unpleasant while driving around in town. I may just go for new rubber, and shift to poly-bushing later if needed.
5: Brake diving. There are different ways to address this, which can be combined. Given that I have a 2.85 rear end out of a 6.3, the most obvious would be to use the brake torque absorbing system. This requires some modifications to graft anchor points in the rear frame rails. It has been done but that particular car I am referring to is not on the road yet, so I don’t know how well it works on a Pagoda. I have the anchoring points that I cut out of a 6.3 donor car.
In addition to the above, weight distribution can be improved. The M117 alloy block engine is the same weight as the M130, but its gravity center is lower. The block also seats a bit more backwards compared to the L6. I’m also thinking of relocating the battery which is ahead of the front axle and replacing it with a dry cell Braille one fitted flat under the passenger side cover behind the seat. These batteries are safe to be fitted inside the passenger compartment. I won’t have A/C (at least at the beginning) and power steering pump will be alloy, further removing weight from the front.
6: Swing axle. I may consider fitting a 6.3 rear sway bar I have, but I would need some input here. The idea is to combat that brutal change of camber when easing on the gas pedal in a curve, which brutally throws the car from understeer into oversteer. It happened to me with a W112 300SE as I had to react to an obstacle while I was speeding in a curve and it is SCARY. I got away by counter steering to lock and smashing the gas pedal to the floor but I was really lucky to keep the car on the road. Now the rear sway bars are said to bring a bias towards more over steer. This may be good on a race car, but not necessarily on a road car. Also, I’m not sure how the sway bar would act in relation with the compensating spring which air suspension car do not have. It looks to me as if they will be acting against each other. I read that the role of the compensating spring was to improve motricity by keeping the wheel inside the curve pressed against the road. So I don’t know. I need help here.
7: A/C. If I install A/C I may consider these compact units they sell which combine heater and A/C, as a replacement of the original heater unit. The reason is that I don’t like the look of the standard A/C system under the dash. So who knows, this may also improve defrost. Any experience here with these units?
Additional considerations:
Alternator clearance: the metal sheeting around the stock air cleaner may be on the way. I need to think about a solution.
Getrag: I’m thinking of using that bracket that was made to adapt the Getrag to the Pagoda, but I first need to see if the Transmission will end up at the same place as with the L6.
Rear axle cooling tube: it interferes with the chassis. I read that blocking the ports creates some oil leakage from the breather. I may modify the shape of the tube and create a bit of clearance room in the chassis rail. I’ve seen it done on a 6.3 Pagoda project in Germany though I don’t want to do something that radical.
This is where I am now. Any help and suggestions are very welcome to help me achieve this. Work won’t stat really soon because I started a new job that really keeps me busy. But it’s good to have ideas circulated in advance as it will help me fine-tune solutions.
Thanks in advance.
