Replacing a missing con-rod cap - OM603 - Page 2 - PeachParts Mercedes-Benz Forum

auspumpen · #16 01-12-2009, 10:02 PM

I'd use an air grinder

Brian Carlton · #17 01-12-2009, 10:10 PM

Quote:

Originally Posted by auspumpen

I'd use an air grinder

That would be dangerous K. You can't control the speed very well and the contact area is very small.........therefore, the temperature will be quite high in a very short time period.

auspumpen · #18 01-12-2009, 10:30 PM

I'm not getting why ya'll are so worried about heat. I've balanced rods and pistons with die grinders on numerous occasions. Use the appropriate grinder attachment and a bit of patience. You should only be taking off tiny amounts and then re-weighing after each touch of the grinder. Time-consuming, but very effective.

Brian Carlton · #19 01-12-2009, 10:52 PM

Quote:

Originally Posted by auspumpen

and a bit of patience.

..........key words there..........

Simpler=Better · #20 01-12-2009, 11:40 PM

Use a stone-based grinder, and don't apply more than a second or two

mplafleur · #21 01-13-2009, 07:11 AM

Thanks for all the advice. It's all good. Let's see how things weigh out today...

mplafleur · #22 01-13-2009, 09:40 AM

There's quite a spread on the other halves.

1 - 435.2g
2 - 451.5g
3 - 439.8g
4 - 431.3g
5 - 449.4g
6 - 450.8g

Using different combinations of big ends and putting priority on using the beefier caps, I only need to remove material from 2 of the end caps. 8.6g on one and 9.6g on the other. This gives me a range of 4g for all 6 complete sets.

Where is the best spot to remove material? At the apex of the cap?

mplafleur · #23 01-13-2009, 08:14 PM

Where do you take material off the big-end to balance the con-rods?

Brian Carlton · #24 01-13-2009, 10:20 PM

Quote:

Originally Posted by mplafleur

Where do you take material off the big-end to balance the con-rods?

The milled side faces is probably the easiest.

DeliveryValve · #25 01-13-2009, 11:13 PM

Personally I would not touch the milled face. But rather shave a little off the top of the apex and the bolt hole shoulders by rounding off the corners first and then sides until the desired weight.

mplafleur · #26 01-17-2009, 11:33 AM

I've balanced them a little ahead of schedule as I took them to a machine shop to get looked at. I noticed than one of them was bent as the two faces were not parallel..

Upon consultation with the machinist, e determined that these were not usable. The amount needed to be taken off the end-cap face would be close to 10 times the allowable 0.02mm before resizing to 51.6mm. The could be brought back to spec with the bore size, but center to center wouldn't meet minimum and my compression would suffer.

I need replacement rods.

Does anybody have any to sell?

sixto · #27 01-17-2009, 12:30 PM

I'd take a step back and look at what I've spent and have yet to spend. Purchasing and shipping from TX to CA a good .96 short block cost me $700. Claimed ~220K miles before the head gave. Hone looked good, mains and rods Plastigaged to installation spec.

Sixto
87 300D

mplafleur · #28 01-17-2009, 07:18 PM

All I have yet to get are the connecting rods, a timing chain, and the 8mm, 4 inch long pin that goes through the head. Everything else I think I have. Although I do have to check my head bolts.

whunter · #29 01-18-2009, 12:47 AM

The connecting rods have been superseded many times due to redesign.
Superseded to MB# 6030303120

There is a footnote.
The old part must no longer be installed.

I sent you an e-mail with more data.

mplafleur · #30 01-18-2009, 01:34 PM

The FSM shows only that the 903.97, 603.96 starting 9/88, the connecting rod eye now has 2 oiling bores. The ones I have, have 1 oiling bore. They are marked 603 07 except for one, which is marked 603 09.

Also engine 603.960 starting 1/88 has 3 bores for lubricating the piston pin.

There are a few versions of these around. I don't doubt that Mercedes states that they want their people to use the latest, but the book says nothing about not using old parts that meet specs.

Bore: 51.6 - 51.619mm
Bushing: 27.018 - 27.024mm (1st ver)
Center of bore to center of bushing: 148.97 - 149.03mm
Difference in weight: 4g
Bores must be parallel.

There are more. but these are the basics.

It'd be nice if i can find replacements with two or three oiling bores, but I'll take what I can get.

I just got a 20% pay cut at the beginning of the year. I can't buy 6 rods at $236 a piece.