Well, it is correct that the intake pushrod should be steel and the exhaust pushrod aluminum on this engine. Either someone simply put in a steel rod because they did not know better, or also because they did not know better, you might find that both pushrods on cylinder # 2 are aluminum. So check cylinder # 2 to see if it has 2 aluminum pushrods.
Forum member Walt Conner has a method for securing migrating valve guides, but the method is not for a casual mechanic and certainly not for a novice.
I don't get the impression you are a novice, but the method Walt has does require some machine shop skills and a thorough understanding of what is going on when trying to correct for out of place valve guides.
Perhaps Walt will chime in here and give his e-mail address.

As to whether someone installed it incorrectly or if it happened by itself. The answer is that it did this all by itself.
Usually, a valve guide moves in response to an overheat event or condition, and an overheat event or condition is usually due to blockage of the cooling air flow from the fan being blocked by obstructions like mice nests or food caches built in the ducts behind the sheet metal.
You already suspect mice chewing on the plug cable, so you may as well suspect that mice at one time built a nest in the cooling duct that led to overheat of that cylinder.
Briggs will sell you a head but they will not sell you a valve guide.

This post was edited by mownie on Sun, Apr 13, 14 at 21:42

Mownie, thanks for the help. yes, there was a mouse nest around the cylinder, and even a dried up dead mouse !

I don't have machining skills (or tools), but I do have access to a good machine shop locally.

Briggs sells valve guides for this engine Part #692057, but if it is exactly the same bore as the OEM, I worry it will do the same thing.

good thought about the two aluminum push rods on the opposite cylinder. I had hoped to stay out of there, as the engine ran pretty smooth on one cylinder, but now, I worry maybe one of the other guides has moved also.

the more I read, it seems lots of people have had similar problems with these engines, has it been established it is always related to overheat? if not, maybe the famous Walt Conner fix should be applied to all 4 guides before they move?

I think the issue with valve guide purchase is that the Vanguard (which is what I think I have), is different than the Intek, in that Intek you cant buy guides, Vanguard you can. Same issue though: same bore as OEM...may move again?

You are correct on both counts, Vanguard and replaceable valve guides. My mistake earlier. I was thinking Intek.
I sent you a PM.
The method Walt describes will hold the valve guides "no matter what"

mownie, thanks again for the help. I don't know how to find PM on this site. where do I look?

click on my profile (click mownie in the heading of any post I have made) and go to "send me an e-mail".
The PM I sent went to your e-mail address that you listed in your profile. So either you have not checked your e-mail, or my message went straight to the spam folder or something.

A PM will show up in the email account you registered with.

Just a point of clarification. If a person has an Intek, you can't repair the valve guides? You need to replace the heads?

With Walt's method, the existing valve guide can be reused. The valve guide must be removed for the machine operation and then reinstalled into the head and secured against future migration. Walt's method is about how to keep the guide from ever migrating again.
Briggs wants you to replace the heads and it is the plain Jane Intek engines that replacement guides are not sold for.

This post was edited by mownie on Mon, Apr 14, 14 at 11:30

Thank you.