Article: Pocher K74 Mercedes Benz Spezial Cabrio A rebuild

[CTDavies]

However, when I mounted all the rockers the whole assembly came apart again, because, as it happened, the push rods turned out to be too long, hitting the recessed spark plug cans, forcing everything apart again. So the push rods were all shortened with my drum sander.

[CTDavies]

When I did the next test fit I realized that the sides aren't really straight, they seem to bow out around the middle, so this time I glued the whole assembly back together again with epoxy to ensure a strong joint and carefully placed it in my small vice using wooden sticks to protect the side surfaces. Also the part with the cylinders was glued in place in the engine bock using epoxy as I wanted a strong bond here as well. You will see why much later.

[CTDavies]

That big black thing I used to hold down the cylinders is a battery used for engine starters on r/c planes. It weighs about 5 kilos, appr. 11 pounds. That should hold the cylinders down until the epoxy sets. I painted the screws on the maintainance plates on the engine block a very dark metalic silver because I wanted them to look like strong metal bolts. The bolt sides were painted as well as my eyesight allows. I always cringe when I see screws and bolts only painted on their caps and not along the sides, I mean, come on, this where is all or nothing makes the difference! This is it for this weekend. The epoxy is still setting and I'll let it do just that over night before I continue. Until then I'll just Ramble On

[CTDavies]

Now that the epoxy has set I put the cylinder head assembly back on again for the next test fit and you can see how it now bows upwards at the ends. I saw this happening earlier which is why I decided to glue the whole contraption with epoxy . Using no glue at all as the Pocher folks intended is a no go here and I was afraid that super glue might turn out to be too brittle, so I'm going to get the epoxy out later plus some large c-clamps

[CTDavies]

So I glued the cylinder head in place with epoxy and with my daughter's help was able to get the whole assembly fixed in these two giant c-clamps. The large finger print you can see on the engine block is probably hers but can easily be polished away again afterwards. So while the epoxy is setting I painted some more details onto the engine accessories (is that the right word?)

[CTDavies]

After three solid hours I had removed all mould seams on the intake and exhaust manifolds as well as the supercharger parts. The supercharger bypass stub was a bad fit and needed some filler around its joints as well as being shortened to the correct length. I shortened it a bit too much as can bee seen on the top filler seam. The parts were then all primed to see if all mould seams had really been removed, but a little bit of extra work might be needed around the two bypass joints.

[CTDavies]

The manifolds already look good in place and I couldn't resist a motivation shot at the end of today's session.

[3.Star]

Hello Chris,

you've done an awesome job on the Benz engine yet. Don't forget to add the cylindrical device located next to the radiator, that is connected to the distributor by a rod and ball joint. Think it is a vacuum valve, which indicates the firing point. Pocher did never replicate it, but it seems easy to scratchbuilt it. Will post pictures of the prototype , when I find them in my mess.
Cheers
Michael

[CTDavies]

Hi Michael,
I've been through my collection of prototype images, but couldn't tell what you meant, so I'm interested in seeing what you want to show me. If it's within my abilities I will surely try to scratch build any missing items.
Yesterday I noticed that the supercharger clutch housing and the actual supercharger housing fit wasn't very nice, but it was easy to screw these two parts together and clean up that joint. On the proto images I have these parts match very nicely and a seam is barely visible. Priming the manifold parts yesterday revealed some spots that needed a bit of extra filler treatment and re-priming before I got out the Metalizers. The exhaust manifold is darker than the polished look of the intake manifold so I mixed some Burnt Metal with Aluminium to get a look that represents a cast iron look. The intake was metalized in Aluminium and then polished. These manifolds don't fit very well to the cylinder head, so I will have to look at this area a bit more over the weekend. Until then I will just Ramble On...

[3.Star]

Hello Chris,
here is a pic that shows the mentioned part: