1958 Johnson 7.5 piston direction

[pro-crastinator]

Hi guys,
My latest confusion is shown with the attached pic.
One piston is easy to see and one is not.
One piston is oriented correctly and one is not.

None of the screws / bolts are tight and now is the time to get this straightened out.

Thanks in advance for your help.
-Bennett

 

[racerone]

Bottom one is wrong.

 

[pro-crastinator]

Thanks. (sheepishly)

 

[pro-crastinator]

No Title

OK. piston oriented -
now I'm looking at rod caps. They seat nicely as shown.
numbers are "facing" different directions.
WHats the prevailing opinion here?

 

[racerone]

Are the wee marks on the caps on the same side ?----You can not mix these things up.

 

[HighTrim]

We cannot tell from the pics if the caps are on correct. As racer stated, they should have hash marks on them to align them. You CANNOT swap between rods, nor flip them. They MUST go back exactly the same way, and from the same rod, as they came off. Always mark them with a sharpie before you dismantle them. They are made from 1 piece, and then "cracked". While tightening down the bolts, wiggle the cap until it rests into its position. Then ensure proper torque.

Also, the rods go in with the hole in them facing UP>

 

[pro-crastinator]

"Also, the rods go in with the hole in them facing UP>"

Please explain this further.

 

[F_R]

Not all rods are the same in that respect. But they usually have an oil hole positioned so gravity feeds oil from the recessed channel on the top side to the bearing(s). Most often seen at the wrist pin end.

Actually, the aluminum rods are not "cracked" as the steel ones are. The rough cap is screwed to the rod, THEN the bearing hole is machined. Point is, swapping them gets the bearing out of alignment or out of round.

 

[pro-crastinator]

No Title

Here we have it.
I looked for the hash marks and took the caps on and off. Keeping them in their own rod.
This is how they feel the best.
No lip inside on the bearing surface, snaps into place readily.
I see where the "numbers are oriented diffently but cant resolve it any other way.

Hash marks don't seem to have a correlation.

Note: when I put the caps on "the other way", it was difficult to put them together and there was a noticable lip inside on bearing surface.

 

[Chinewalker]

If memory serves, the 7.5 rods have a rough alignment nub cast into the sides of the rod cap end, nearer to the bearing surface portion, not the outer rim. Could be different, though, depending on which rod castings you've got. Are the oil holes up on both rods?

I always mark the rods and caps with an awl when I remove them - one hash mark across both halves for top, two for bottom.

 

[pro-crastinator]

No Title

Oil holes up.
The oil access to lube the bearing looks like its the notch in this pic.
The oil can make its way down the channel and lube the bearing.