I've managed to bend the exact same push rod twice in a matter of two weeks, neither time was it being driven hard. Does anybody have any idea on what might be causing the same push rod to bend while all the others are perfectly fine?

 

It could be valve train bind, bent or broken rocker, bent valve, valve adjusted too tight (causing piston to valve contact), pushrod too long, etc.

Probably, the issue has to do with adjustment though.

 

Adjustment won't cause a bending pushrod unless it results in binding. Probably a piston to valve issue or a rocker arm related issue, it's binding up the valvetrain motion and the force gets relieved through the pushrod. Is the rocker arm clearing the valve spring and mounting location? Turn the engine over by hand and check for binding.

Edit: Just though, couls also be a coil binding issue. Haven't had any valve float either, have you?

 

Ummm, I would venture to say that valve adjustment is the cause of quite a few bent pushrods, I am of the opinion that a lot of these issues are caused when the valves are adjusted so tight the piston "kisses" the valve. Not so much with an experienced builder but.....

I didn't want to write a book....

 

overrevving (valve float) can cause it as well. i checked my rev limiter yesterday, and figured that the 12V source at the connection was gone. fixed it, so I should be safe again. I'm quite sure that's how I eneded up withg bent pushrods

 

Sticky valve bent one of mine a long time ago...

 

Valve train bind has already been mentioned. But what hasnt is the lifter. If you have hydrolic lifters it is possible for the lifter to stay in the extended position and not relieve down as the valve train heats up and expands.

If it was me. The cheapest thing is to replace the lifter and see what it does. If the pushrod bends again then you can see about a head job for the rest of the valve train.

 

The lifter cup would have to be totally frozen in place to do that(whether from being mechanically stuck or if the hydraulics are plugged up), in which case there wouldn't be proper preload and it would adjust like it was a solid lifter with lash. And if there's slight valve-piston "kissing" then it's not so much an adjustment issue, but a PTV clearance issue. And if the PTV clearance is SO tight that a slight valve misadjustment causes contact, then the PTV clearance was incorrect when the engine was built in the first place.

First thing's first, since PTV contact is a big cause of bent pushrods, do a compression test first. If compression is low on the cylinder in question, or it leaks air out of the intake/exhaust port that has the bent pushrod, then chances are that's the problem. Also, put a good pushrod in place, adjust the lash, and turn the engine over by hand and see what it does. Look to see if the coil windings in the springs are making contact, or getting really close. The coils need to have enough clearance to account for thermal expansion and vibration when in operation. Even if you have clearance when cold and not running, heat and vibration can cause the spring to slap itself and damage the valvetrain. Measure clearance with the valve fully open, and remember that the lifter will be compressed. So it could also have clearance when cold but when running and the lifter is pumped up, the clearance goes away(coil bind is one of the other largest causes of bent pushrods). Also check to make sure the rocker body isn't making contact with anything like the trunion mount or the spring itself. Some Ford rockers don't always clear larger diameter springs.

Those are the easiest problems to find, so target those first. If it's none of those then we can start looking at the less likely stuff.