2 bent push rods- Why?

[rollguy]

I found out the lack of compression problem with my SX4.  I heard somewhere that the push rods can come out, so I decided to pull the valve cover to see if that was the culprit. 

AI found two bent (Z shaped) push rods.  A trip to my local Pick-A-Part, and I found an old DJ.  I could not get the cover off (it had 1/4" hex screws), so I tried a 4.0 L in a Cherokee.  I was not sure if they were the same length, but the valve cover was easy enough to remove to check.  I got 2 push rods for $1.99 each.   After arriving back home with the parts, I put them down in the holes and they were too short!  Grabbing a flashlight, I peered down the hole to see the lifters laying sideways in the engine!   I was able to use a magnet to pick them up and get them back in the holes without having to pull the head (Thank You LORD!).  I put the rockers back on and had a friend crank the engine to make sure everything was OK. Immediately one of the push rods bent again.  I was not sure why, but back in the car to Pick-A-Part for more push rods! (I got 4 this time).   I took a socket and hammer and whacked the top of the valve spring top to loosen it.   That seemed to work, as after putting it all back together, it cranked for a long time an no parts broke, bent or flew off!.  I ran out of time, so I will finish putting it back together and fire it another day.
Does anyone know what causes the push rods to bend?..Rich

[Hawk258]

it sounds like your valves are seized not sure why, but I suggest a tear down of the head and have it cleaned with new valve seals and check for burrs in the valves themselves, Not 100% but that is what I would check, also which cylinder or cylinders? If it is 5 or 6/ or both then I would check for carbon build up on the head of the piston about an inch tall on #6 and 1/2 an inch on #5. I know I had some bad rings and stuff when I first bought my SX/4. You may be in for a bit of work, but since you are already halfway there it wouldn't hurt to take a peak.

[eaglefreek]

I had a problem with bent pushrods. After installing new valve springs I cranked the engine and instantly bent a couple pushrods. Bought new ones, installed them, cranked the engine and bent the 2one new ones and a couple more. It was suggested to me that the lifter may have over pumped and to to install the pushrods and let it sit for a day or two. I waited 24 hours,  cranked it up and no bent pushrods.  That was 2 years and 20,000 miles ago.

[rollguy]

The engine has sat for more years than it has been used.  When I first built the car, I used it several times a month (off road).  After the first couple years, I only used the car twice a year.   I have to say that there is probably less than 5,000 miles worth of driving on the engine since the rebuild (12+ years ago). All that to say that it does sit a lot.  I would agree about the stuck valves, as they probably have not had much lubricating since the lifters popped out of their holes. After the second trip to P-A-P for more push rods, I lubricated the valve stems (as much as I could through the springs) and moved the offending valves up and down by hammering a socket against the spring retainers.  That must have worked, as it cranks good now with all rockers and valves moving freely.

[Jurjen]

On my Yamaha TX 750 with sticky valves I put some engine oil in the gas (1:150) like a two stroke. That helped, but note that it will only help the inlet valves.

[carnuck]

80-82 4.2L also have an issue with #2 valveguides from the factory in about 20% of the cars and Jeeps.

[GRONK]

I have a distributor gear on a power drill attachment for my Jeepster Commando.  It gets drived 1 or 2 times a year.  before starting it up each time, I pull the HEI distributor and "prime" the system with the drill.  This helps lubricate everything before initial start up.  I do this because that's what I was taught to do on older engines that sit more than drive.  It was under $12 to make the primer and really doesn't take very long to do.

Just a suggestion for starting those 1ce a year drivers and 4x4's.

I know they do this with race engines at the track too.

[BenM]

The 4.0 rods are supposed to be different sized then the 4.2 rods, and that could cause them to continue bending.

I agree that it's probably varnish on the valves. You should drain the old gas out of the tank or it may re-occur.

[captspillane]

The engine I just rebuilt had low miles, yet it took three or four times longer to clean than I expected. Years of oil inside had a layer of gunk everywhere. I ended up soaking the lifters in degreaser for a few days because there was visible junk built up around them. I also took an old lifter and drilled a hole in the bottom and made a tool that I could use to clean the cylinder bores down with. I've heard of people draining a third of their oil out and filling it with diesel oil or ATF to act as a lubricating degreaser, then running the car for a 100 miles or so.

The first picture shows the difference in height between a 4.0L and a 4.2L pushrod. The 4.0 is shorter. The second picture is the tool I made.

[mudkicker715]

[img width=775 [img width=775

Lifters are also different