We quickly became very pleased when we started studying this swap. This was going to be even easier than we thought.
By 1970, Mercedes used a much different transmission. So, the transmission mounting plate off the 2.8-liter engine was different. Fortunately, removing this plate from the 230S engine was easy and it fit right on to the bigger engine.
The clutches appeared to be exactly the same, so we reused our original clutch. While the flywheels are unique (and balanced) to each engine, they are roughly the same size and shape. There were no clearance issues. Even the pilot bushing was the same.
So, other than switching the mounting plate for the transmission, (a half-hour job) nothing at the rear of the engine needed to be changed.
While we couldn’t find the correct clutch alignment tool, a smaller one with some tape wrapped around it worked fine to get the clutch lined up.
Around the front of the engine, we determined the upper radiator hose is different. A quick swap of the thermostat top plate fixed this, as our earlier one bolted right on. The coolant lines that run through the carbs used a slightly different setup, but didn’t present any real problems.
By 1968, the water pump fan pulley had gone from three bolts to four, but we just used an earlier water pump and solve this problem.
Our 1970 engine had mounting for an oil cooler and oddly enough, that oil cololer had been blocked off. It seemed to have been done by the factory, so perhaps it was optional. We will eventually take advantage of that optional oil cooler, but for now we kept things simple. We put our old oil filter mounting plate on the newer engine and it all bolted up perfectly.
We ended up using our original distributor and Zenith carbs with the jets and needles out of the newer engine. The carbs that came wither our engine were tired. We knew ours worked well, and they had just been rebuilt. Other than some minor revisions—apparently for emissions compliance—the carbs were the same.
We were nervous that the larger and differently shaped shaped oil pan would give us clearance problems, but were amazed when the whole assembly just dropped right in. Did we really just go from a worn out 2.3-liter engine with five main bearings to a great running 2.8-liter with seven mains for just $600 and a couple of evenings work?
A turn of the key and a test drive confirmed that we had indeed. Sweet!
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