Type 4 Connecting Rod Direction

[misszora]

Hey there,
So the matching numbers on the connecting rod caps and bodies all face the same direction when connected to the crank shaft. Do the numbers point toward the flywheel or the fan?

thanks!
- Paige

[ruckman101]

There are bumps, or small rises on one side of the connecting rods that should be oriented up, at least for a type 1 engine. Pay attention that two of the rods are oriented correctly, not going the wrong direction from where they would be if connected to the pistons. I've seen that happen. There is a slight offset from center with the rods for some concern of engineering, so they can be connected upside down. Things will run, just not as long.


neal

[misszora]

I just realized that the numbers are not going to be facing the flywheel nor the fan because they will be facing north or south, if you will. No bumps for type IV but the Wilson book mentions that the bearing tangs should be at the bottom of the journals when the crank is horizontal. I am doing the assembly with the crank mounted to the flywheel so it is vertical.

What I'm thinking is imagining that when it is horizontal, the two timing dots that align with the cam shaft's singe dot will be positioned around 4 o'clock and I can determine the "bottom" of the journal by that. Is that correct?

[SlowLane]

"Bottom" of the rod journals will be utterly independent of the timing gear dots. The rod orientation to the outside world doesn't rotate with the crankshaft, but rather reciprocates.

With the crankshaft vertical (presumably clamped in some sort of jig), you need to identify for yourself which journals go with which cylinders, then picture which way the rods will point for each cylinder/journal. From that rod orientation, you should be able to determine which side of the rod will be "down" (ie. closest to the bottom of the crankcase).

From memory, the cylinder/journal ordering from the flywheel to the rear of the engine should be 3, 1, 4, 2.

Does that make sense?

[misszora]

We actually figured it out, did an imaginary lay down into the half case to confirm. Thanks!
I spaced on the fact that I would be able to rotate the crankshaft to position the timing dots.

[Amskeptic]

We actually figured it out, did an imaginary lay down into the half case to confirm. Thanks!
I spaced on the fact that I would be able to rotate the crankshaft to position the timing dots.

The Type 4 engine's connecting rods do not have the offsets as found in the Type 1 engine. The raised casting marks must be obeyed with the Type 1.

I came up with my own rules regarding the tang orientation on the Type 4 engines, and none of mine have blown up or shown premature wear as a result.

The crankshaft rotates *clockwise* as you look from back(fan) to front(flywheel), right? The right side rods push the journals *down* and the left side rods push their journals *up*.

I choose to have the cut-out tangs opposite the firing push points. That would mean the right side rods I would have the tangs up, and the left side rods would have the tangs down. LIKE IT MATTERS ....
Colin

[misszora]

I guess the important part is that the rod cap numbers correspond to the correct connecting rod and face the same direction when connected to each other.

[Amskeptic]

I guess the important part is that the rod cap numbers correspond to the correct connecting rod and face the same direction when connected to each other.

This is true that.
Colin

[misszora]