Cylinder Block Waterways

[DavidBrough]

I have an early 280 on which I’ve had some ongoing issues with cooling and thought I would check the waterways in the cylinder block whilst my body shell is being dipped and have a few questions.

I’m looking at the small holes and slits between the cylinders and wonder what size they should be as mine are inconsistent. The holes on the right side of the block are 6mm at the face tapering to 5.5 whereas those on the left are 5.5mm tapering to 3.5 and 3mm with two being only 4mm on the face. I attach a couple of photos with the smaller holes clearly visible in the lower middle of the shots. Does anyone know how big these holes should be and if mine are the correct size or if they have become silted up should I drill out the smaller ones to make them all the same size?

On looking at the slits I notice they have a varying depth of between 18mm and 7mm and wonder if these may have become silted up?

[tel76]

Hello David,
I have just refitted the new pistons into the block, i will measure the water holes and slits on Monday and report back.
If you feel like a challenge,remove the water side plates and then give the block an internal high pressure steam clean you will be amazed at the amount of crap that comes out.
One word of warning,some of the side plate retaining screws will break off.
As a matter of interest, what  thickness of metal  do you have between the cylinders and what oversize is the block at?

[DavidBrough]

Thanks Eric. I've already removed the side plates and thankfully all the bolts came out OK, the metal between the cylinders measures about 6.15mm although I only have an ordinary vernier caliper and it's not easy to get the reading that accurate. Not sure about the pistons but I do know they are oversize but can't see any obvious sizes stamped on them, the bores seem to measure about 87.33mm but again I'm not sure how accurate that really is.

[tel76]

Hello David,
Information as promised -
The slot/slit is 17mm deep at the central position.
The hole sizes are as follows -
  1 - Between 1 and 2 cylinder 7/32 both holes.
  2 -    "          2 "    3    "       7/32 manifold side,
                                           5/32 Fip side.
  3-     "          3  "   4    "       7/32 both holes.
  4 -    "          4  "   5    "       7/32 manifold side.
                                           5/32 Fip side.
  5 -    "          5  "   6     "      7/32 both sides.
I used my drill set to determine the hole sizes hope this info: will assist.

[DavidBrough]

Thanks Eric, that's useful. It seems that my holes are about the same as yours and that there should be two smaller ones. Do you know if yours are a uniform size as mine seem to taper slightly as they go into the block particularly those on the injection pump side. After much scraping around I managed to remove a fair bit of crud from the slits and they now measure the same as yours.

[tel76]

David,
The holes are uniform all the way down,i was able, without any resistance to push the drills all the way in.

[DavidBrough]

Thanks Eric, mine must defiantly be silted up then as they do narrow quite perceptibly as they go down into the block so I'll get my hand drill out and try to gently ease the muck out as I don't want to damage anything.

[Benz Dr.]

The slots are not the same depth all the way across. They're milled with a round blade and will be deeper in the center between the two holes.
This was done to provide extra cooling between the cylinders right at the top where heat would be an issue.

[DavidBrough]

Thanks Dan, after much scraping and cleaning I think I've removed all the silt and now run a drill down the holes which are all of uniform 6mm size with the two smaller ones being 4.5mm hopefully this will help alleviate the cooling issues I've been having