Rebuilding my m103 Brabus 3.6

[brabus3.6]

I recently posted about hesitation around 2000rpm on my Brabus. When cylinder leakage was measured it ranged between 52%-64%, heard from the bottom end! So I've now stripped the engine down completely.
The block has 2-3 thou of wear and so is shot. I'm getting a standard 300e block and having it bored to spec (92mm). Brabus want £800 ($1600) for piston rings and £580 ($1200) for a headgasket, ridiculous.
So, I think I may go with Gapless Top Rings, which seem like a more advanced piston ring than would have been offered at the time my engine was built.
As for a headgasket, it seems the basic gasket layout (position of bore, water & oil galleries and sizes) is the same as an M120. Cosmetic's left hand bank Zonda gasket(!) seems to do the trick but is 1mm small in bore size. I've sent a gasket over to the US for inspection and I'm praying the gasket is the same bar this as Cosmetic will do a custom bore size. Anyone ever used an MLS gasket on a benz, I'm guessing it's a better solution than copper?
Incidently the Brabus gasket blows around every 10,000 miles anyway and is just a standard Victor Reinz, nothing special!
Any tips on re-assembly (i.e. assembly oil?) and running in etc?

[jhodg5ck]

I would run the benz rings...these engines are Very particular about the style of ring they run. I knew a fellow who ran gapless and they ate his cylinders.. That's not to say there wasn't another issue @ hand, but you can Know that the MB style rings work in this bore.

The MLS gaskets are good from what I hear..I don't see any reason why it shouldn't satisfy your needs.


Have you considered any other upgrades while you have the engine out, ie oil squirter's to the back of the pistons, perhaps converting over to studs instead of head bolts... I'm sure that would help with the head gasket issue in the long term.

Jonathan

[brabus3.6]

Oil squirters? Are they normally used in diesel engines?

ARP don't seem to do a head stud for the m103, do you know of any companies that do? Why are studs better than the MB stretch bolts.

On the rings issue I've email KS to see if they can supply me with the original rings. I saw a thread were m.b. doc mentioned using gapless in an old diesel engine with success but thanks for the warning.

[jhodg5ck]

Oil squirter's are used in a rash of high performance gas engines.

As for studs, they allow for far better tightening of the head to the block. Head bolts are a concession to cost. ARP should be willing to make up a custom set of fasteners. Should you choose to pursue it I would be interested in a set or two for future projects.

Jonathan

[t walgamuth]

I have no specific info about studs vs bolts.

We had a fairly long discussion regarding them a year or so ago here. I know that a lot of Ferrari and race motors use them, but I am not sure they actually automatically assure more successful sealing than stretch bolts. Since race engines use them one advantage might be that they are more forgiving if you are taking the head off often, and of course not being stretch bolts, you would never have to buy new bolts again. So they would save money that way too.

For the kindof money you are speaking of you might be able to get custom pistons and rings from one of the high performance companies.

Good luck.

Tom W

[jhodg5ck]

Any performance engine builder will tell you studs are the way to go. I believe it has quite a bit to do w/ how the force is applied with a stud vs bolt, that being a stud generates less less stress then a bolt.

To quote Corky Bell "head bolts are an accountants decision. A head stud is an engineers". I know Caroll Smith has echoed this statement as well, but I couldn't find it in his book quite as readily!

Jonathan

[EliotW]

Did any of the other tuners make a M103 3.6? I remember reading scuttlebut that the Brabus 3.6 was pushing it.

Incidently the Brabus gasket blows around every 10,000 miles anyway and is just a standard Victor Reinz, nothing special!

[brabus3.6]

Yes it was pushing it, or at least my engine is. Brabus made 3 3.6 engines, with 91mm, 92mm and 92.25mm bores. My engine has the 92mm bore which is where the problem lies as the increase in bore along with the water jacket inbetween the cylinders leaving very little room for the compression rings of the gasket to seal. AMG also did a 3.6 m103, as did Renntech, but they both went for a 90mm bore and so don't suffer this blow-out problem (also meaning Renntech owners use a C36 AMG gasket, peanuts!, yes an M104 gasket is the same as an M103 one, I've seen them side-by-side).
Incidently, for anyone who cares to know, the stroke on my engine was increased using the original connecting rods but a new chrome molybdenum crankshaft.
I'm contacting Top End Performance to see if they get hold of some studs for a m103. Also, I'll ask how much Pauter titanium connecting rods will be.

[brabus3.6]

Head studs
M103 Head Studs vs. head bolts