03 August 2025:
The "507" engine was put up on a stand last night. Thought that was good enough for the night, but decided that it was time to verify that this really was the engine as advertised. As mentioned in an earlier post, this engine is supposed to have an M159 rotating assembly, but this is really hard (impossible) to verify from the outside. Since the C-Class oil pan and pump will not fit in a Crossfire, these were going to have to be removed, no matter what. Once the lower pans and upper pan were off, you could see nothing. Well, almost. There are four slots that oil drains back to the pan from in the bedplate/windage tray. Other than that, you cannot see the rotating assembly at all. The slots are roughly 1/4 x 1" in size. Through them, you can barely, barely see connecting rod caps. Removing the intake showed one curious thing on the intake manifold gasket:


The gaskets are marked M159. That is very curious, given that the heads are supposed to be 'regular' M156, and the intake is most certainly not M159. Hmmmmmmmmm........
Time to bust out the bore scope! These pics are very hard to read, but here are some:

View of the underside of the piston.

View of the underside of the piston.

View of the underside of the piston.

Fuzzy pics, but I am looking for some specific things, like casting lines. A cast piston for an M156 looks like this picture (from eBay):

Cast M156 piston (used, on eBay)
Looking at the cast piston, you can see the casting lines and marks associated with a mould. Notice the borescope pics show only machined and smooth metal underneath. OK! Good news, pistons look the part. Let's continue!

Looking at the crank, there are these odd round metal discs in the counterweights. Also, some knife edge machining of the counterweights.

Strange metal discs

Machine work on the counterweights

The round discs are almost certainly heavier metal added in for balancing. Common practice on cranks with machined down counterweights. Also, not pictured, it looks like there is not center counterweights?!?!? Time to consult the google!




That took all of 5 seconds, and then the awesomely entertaining, and really smart Youtuber Tasos Moschatos had the answer! If you have never watched Tasos' videos, I highly recommend him. Guy works on some really cool stuff!

So why not just remove the bedplate and verify everything? Well, very simple - cost. To remove it will require replacing all of the main bolts (one-time use) at something on the order of $25-40 each (4 per cap!) and new main bearings. I'll work with just the info on hand. Bottom line, this is a real "507 Edition" engine, and it will be the basis for this car's swap. Not looking for any more power, but this is how any racer would build an engine for a project car if you could, and it should prove to be durable.

The next few steps with this car will be less dramatic. A lot of wiring for the dash, front and rear SAMs, and preliminary ECU wiring. All stuff that just does not show up too well. Also, the project is going to stall over the next several weeks due to life commitments. As a result, the M113K Crossfire will be the one we will take to this year's Crossfire Fall Rally in Helen, GA. I know, poor baby!