ARP Main Studs for the M113k

ARP doesn’t sell a main stud kit for the Mercedes-Benz M113k engines, but they do make studs and bolts that will work. I was able to source individual parts for each of the mains – inner and outer – as well as the cross-bolts that come in from outside the block.

I started by measuring and filling out the Head Fastener Measurement Sheet, found on page 22 of the ARP catalog. Even though it’s meant for head studs, it works great for mains as well; you just don’t have a gasket to factor in. Once I had all of the measurements recorded, I called ARP and gave the guy who answered (Sam) the relevant dimensions. He was able to find existing part numbers that would work! I even measured each of the cross bolts that come into the caps at 90 degrees from the outside of the block. For those, we had to get creative and use some larger diameter 5/16″ washers under the heads to match the size of the OEM E-Torx bolts.

The whole order came out to about $300 and everything was in stock so I had the kit a few days later and verified fitment by dry-fitting everything. Looks like it should work out great! This should give me more stable main caps, and will definitely be a plus not having to buy new bolts every time the caps need to get torqued.