Pushrods keep bendind
 

a friend of mine has a 1996 ford f150 2wd with a 302, he recently took it in to have new head gaskets put in, a week after he got it back it started to act up and the top end of the motor was knocking, he took it back to the shop and they said it was a bad lifter, they took it apart and replaced 2 lifters and 2 push rods that were bent, after he got it back it ran good for a week or so then started acting up again, he took it back and they said it was a lifter again, they took it apart an found 2 more bent pushrods and 2 broken rocker arms, what would cause this to keep happening.

Cam timing is wrong.
Cam lift is too high.
Wrong style of valve stem seals installed causing coil bind.

Tough one, they ONLY replaced the head gaskets, didn't take the head apart?

Was the head milled, did they take it to a machinist?

Was it the same 2 valves again?

I would guess that somehow in all that was done a couple valve stems got bent causing them to bind up some and overstress the lifters/pushrods.

yes it was the same two heads, the shop that put the heads in said they dont know what would be the cause, the heads have not been taken to a machine shop, they are all original valves and guides

But is it the same 2 valves? You said on 2 occasions they had to replace parts on 2 valves, which 2 and were they the same 2 on both occassions?

It seems like some info is missing here.

At the onset of this problem...why did your friend have the head gaskets replaced? Water in oil, low compression, wouldn't run, etc.

If he troubleshot it down to head gaskets, how did he come to that conclusion?

If we start at the beginnig, we may be able to figure out how he got to this point.

same reason anyone would replace the head gaskets, antifreeze in the oil and exhuast

jeffmeyers 351, I'm sorry if I may have offened you, I assure you that wasn't my intension, I just wanted to be sure the orginal problem was taken care of and the bent pushrods aren't a symptom of the orginal problem.

If nothing else but the head gaskets were replaced, and all parts were reinstalled in the correct position, then nothing should have changed. By that I mean the distance the valves are opening.

If however, when the heads were removed and all the parts were just thrown into a box and not properly identified then the push rods/rocker arms are most likely going to be missed matched.

Could mismatched parts make a difference? I would think the differences would be so small that it wouldn't really matter....but maybe it does.

My Ford maunal basically says during removal identify all parts and for assembly reinstall them in the orginal position and oriention. It goes on to say that if parts are replaced then check valve clearance and if necessary install a longer or shorter pushrod. There is also a procedure to identify the correct lengths pushrods.

My manual doesn't give a pushrod length...maybe someone could chime in with the stock lenght as a good starting point.

Anyway, I hope this helps.

if the mechanic only did the head gasket, sounds like he mixed an matched the push rods to different lifters/rockers.

Pushrods are all the same lenght

Sounds like he needs to find a new shop..

he took it to another shop, they took it apart and found that it the pushrods they replaced were and odd size, they went ahead and replaced all pushrods and lifter with the right ones, he got it back today and its running good now

Glad he got everything fixed up. :)