Johnson AD12 connecting rod

[stanley]

Trying to build one decent motor from parts pile.I have rods marked 277196-1 and 277196-2.Is there a difference that requires a -1 and a-2 to make a pair or can I use two -2s ?

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[chris-p]

I cannot remember the difference off hand between the casting numbers. Ill check my parts to see.

If they are the same, make sure you go over those rods closely! They are prone to failure. If I had a dollar for every AD parts motor I have had with a hole through the block I would be rich.

So many uneducated people out there NOT running them on 16:1 like they should be. These motors MUST be run on a 16:1 mix, or else.

Make sure they are not scored, worn out of round, worn out of size, etc… before installing, or you are just wasting your time.

Personally, when I rebuild an AD, I install NOS rods. That’s just me though.

[adam1961]

I think that these rods are just different casting numbers. Does the -1 rod have the oil groves on the other side of the big end? I seem to remeber looking into it when I did my AD and think that the -2 was a later casting that may be better??? As Chris mentioned, good used AD rods and cranks are hard to find. If you have two rods that fit the crank well and work, I would use them and have it making smoke again.

[stanley]

I can’t tell where the oil grooves were on -1 rod.If you look at the picture,the cap was loose on that one and the rod flopped around and ground the sides off.The two -2 rods have grooves on both sides.I’m going to inspect it well,as Chris said,and put it together and run it,like Adam said.All of it is leftovers,so nothing to lose.

[dan-in-tn]

Seems like I remember the -2 casting having the slash marks on both sides of the big end? That way the rod can not be put in upside down. It was a manufacturing thing as well as service aid. I usually spend a little time making sure no flashing is left so oil can get into the big end easily. I have considered adding a hole in the small end well? That way the wrist pin would be oiled better, but decided against it since wrist pin oiling is not a problem on this model. Don’t fix it if it ain’t broke!

Dan in TN

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