Main cap orientation

[CrazyPrime]

I got my crank in and I have a question about the main caps, basically when I took them out and kept them in order but I don't know which direction they are suppose to be orientated does it matter? I originally put them in the way I thought they went but they didn't seem to fit then I flipped them and they fit alot better, does it matter which way they go? Here is how I currently have them







This is after I flipped them the opposite way I "thought" they went, any help is appreciated.

[jlevie]

Personally I would not re-use bearings. Measure the main and rod bearing journals to a tenth and pick the "color" of new bearings that matches up with the journal dimensions. Also check for out of round wear. Since the tools for this are a tad pricey if this is not something that you expect to do several times it would be lots cheaper to have a machine shop take the measurements.

There are two types of bearings used based on date of manufacture. Make sure that you get the correct ones for this engine and get new rod bolts as they are one time use bolts.

[CrazyPrime]

Thanks but I'm not talking about the bearings I'm talking about the main caps themselves not the bearing. I am just wondering which way the main caps go. Example do the main caps go bottom of numbers on caps to the front of the block or the bottom of the numbers to the rear of the block?

[cabriodster87]

It is critical that the caps are put back EXACTLY where they came from. They are line bored. 1-7 goes front to back, imho put the caps in and torque without the crank and measure everything to be sure.

[95BMWIC]

I just did this with an "e" model - but I think it is the same.

When you pull the main cap off- look at the slots in the bearings.

I believe the must match up from the cap bearing to the other journal bearing.

My slots on the e engine (with engine upside down and I was standing at the front of the engine (intermediate shaft to my left side facing me -see pic)) - the slots are situated on the right side from this point of view.

[95BMWIC]

Also - main caps are numbered and start with number 1 from the front (same position that I explained before)

[CrazyPrime]

Ya I know what order they go in, I just didn't know which way thanks for clearing it up 95BMW.

[Cabriolet]

Ya I know what order they go in, I just didn't know which way thanks for clearing it up 95BMW.

they only fit one way. you'll see that they get jammed up if they are flipped 180.

[CrazyPrime]

Well boys looks like a F'd up again, I didn't mark how the rod caps go on. I'm guessing they are specific also, just like the main caps I numbered them but didn't mark which which way they go. Please help.

[TobyB]

Yeah, 95 said it- the indented notches for the bearing caps are both on the same sides.

As to which cap goes on which rod... the only way I found to figure that out after the
fact was experimentation and plasti- gauge. It sucked on a 4- banger,
I imagine it will suck much worse on a 6.

t

[whodwho]

...
As to which cap goes on which rod... the only way I found to figure that out after the
fact was experimentation and plasti- gauge.
...

The rods and caps will have random numbers on the sides near the rod/cap spit, the rods and cap numbers will match.

[95BMWIC]

First - just double check the arrows on the pistons - to make sure they are all pointing in the proper way (to the front or radiator end). See pic #1 these are e pistons - but the i pistons should also have it.

From the bottom looking at it from the orientation I stated earlier - you will have a couple of slots in the bearings - plural (top and bottom) -(they are offset) and for me were on the right side of the piston cap when installing . See pic #2

the stamping does not necessarily tell you the orientation ( I have one piston rod cap that is backwards from the rest) - be aware that each cap is matched with each piston rod - if these are not matched correctly you could have some serious issues (because they were balanced and matched in assembly).

for my last pic - I marked each cap to know the orientation and the sequence..

[digger]

For the rod caps you can get some idea by looking at the details on the edge and matching the appearance either side of part line There is usually a subtle difference

[95BMWIC]

The rods and caps will have random numbers on the sides near the rod/cap spit, the rods and cap numbers will match.

True.. Have a pic of that too somewhere..


The numbers are stamped on one side - very faint - same number top and bottom. The other 5 pistons were all different random numbers..

[TobyB]

Good to know- Thanks!

That's not true of the earlier M10's...

t