I found that the 351w in my 68 mustang has 8 bent push rods. 6 exhaust and 4 intake. Some of them are so bent that they are scared from making contact with the head. I took off the timing change cover with the assumption that I would find a slipped timing change.
Much to my surprise, the timing has not slipped and the timing chain and gears look to be in good shape. What could cause all of these push rods to bend?

This is a 351w out of a 1975 Gran Torino. The motor has 50k miles on it and is mostly stock. It has a mild cam and stock heads. The motor had been running OK (not great) with the exception of a lot of valve train clatter. I had assumed that the timing chain had slipped because I had just tried to time up the engine with a timing light and the initial timing had to be set to like 20 to 25 degrees to get it to run right.

 

INstalling an adjustable valve train on non-adjustable valve train heads?
Over tightning the lash?
Over revving

Lots of things can cause push rods to bend. Replace with a chromo moly set.

 

Valve springs, when you use upgraded valve springs you need to get hardened push rods. My bro had a similar problem with his stang when he put some '70 351 heads on his 302. They had double valve springs, he bent 2 pushrods within the first 10 mils.
-P.

 

Stuck valves will also cause bent pushrods

 

Have the heads machined for screw in studs and guideplates. Then get a set of poly-locks so you can adjust the valve lash. The factory push in studs will push out over time, especially when you start increasing the valve spring pressure and cam lift.

Stock pushrods are marginal even in stock engines. Along with the oil pump shaft, they should be replaced with any engine rebuild.

 

I had a 78 bronco with a 351M that was totally stock and one day I was taking off from a light and I heard it backfire and then took off like normal. After that it had a valve train tick, and a bit less power, so after a couple weeks driving, I decided to figure out what it was. When I pulled the drivers valve cover, I discovered a bent pushrod. I wasnt even beating on it or anything, just like that it bent. Somehow I dont see this happening to all 8 (or 10, depending on what math you use) of your bent pushrods tho.