Are pushrods and springs really needed?

BFT · Jan 23, 2012

A bent pushrod or rods is capable of keeping the valve open. What happens when a valve stays open? The piston punches the sh!t out of it, possibly forcing the valve up breaking retainers busting out keepers...etc.

Putting a stiffer valve spring is asking a bit too much of a stock push rod. Like I said before, stock pushrods are good with stock valve springs.
How do you know that the pushrod is not deflecting and not letting the valve open up all the way?

mike@haller's · Jan 23, 2012

Those parts were secondary damage. When the rod broke out of the piston the motor was still spinning. The rod basicly pushed the piston up slamming it into the cylinder head. It then hit the valve hard enough it broke the valve and shoved it up through the head knocking both springs out of the head. One broke one didnt. It also went high enough it broke the tip off the injector.

Black_Lightning91 · Jan 23, 2012

Forgive me but Im not seeing how a bent pushrod can hold a valve open. Can anyone give me some info on this.

BFT · Jan 23, 2012

Black_Lightning91 said:
Forgive me but Im not seeing how a bent pushrod can hold a valve open. Can anyone give me some info on this.

What is the push rod/ rods job?

lubeowner · Jan 23, 2012

BFT said:
What is the push rod/ rods job?

So what you therorize happens is the push rod opens the valve, then bends, then gets hooked on something to hold the valve open, then the piston comes up and smacks the valve?

I contend that a bent push rod is shorter then a straight one. Thus the bent one does not open the valve at all or not all the way. The push rod may bend on its own but doesnt cause any damage. Or a rod may bend as a result of some other damage, like floated valve that bent and wont open. Just as 97singlecab said.

BFT · Jan 23, 2012

lubeowner said:
So what you therorize happens is the push rod opens the valve, then bends, then gets hooked on something to hold the valve open, then the piston comes up and smacks the valve?

I contend that a bent push rod is shorter then a straight one. Thus the bent one does not open the valve at all or not all the way. The push rod may bend on its own but doesnt cause any damage. Or a rod may bend as a result of some other damage, like floated valve that bent and wont open. Just as 97singlecab said.

the rod never bent on eriks truck, just the piston and rod werent attached anymore.
bent or not the push rod still goes up and this time at a different angle. i dont know how many motors you have gone through in order to prove what you are trying to say. ive been through enough to know what causes the problem but not all the time is it just the pushrod.

have any of the pushrods that started on this thread been checked to see if they are straight?
just like a pool stick, it looks straight till you roll it on the pool table to find out its bent

Wayne · Jan 23, 2012

lubeowner said:
So what you therorize happens is the push rod opens the valve, then bends, then gets hooked on something to hold the valve open, then the piston comes up and smacks the valve?

I contend that a bent push rod is shorter then a straight one. Thus the bent one does not open the valve at all or not all the way. The push rod may bend on its own but doesnt cause any damage. Or a rod may bend as a result of some other damage, like floated valve that bent and wont open. Just as 97singlecab said.

contend all you want, but when a bent push rod gets loose there's a good chance it becomes unseated in the lifter allowing it to sit on the higher edge of it. End result is the distance between the cam lobe and rocker arm grows about 1/4" not factoring in the shorter straight distance between the ends of the push rod.

Now think what kind of damage you would have if you essentially replaced a hydraulic lifter with a solid lifter, then added 1/4" to the length of the push rod. I replaced a 6.0L engine with tha exact senario because the rocker arm actually broke when the valve got slapped by the piston caused by hanging out when the push rod "grew"

lubeowner · Jan 23, 2012

Wayne said:
contend all you want, but when a bent push rod gets loose there's a good chance it becomes unseated in the lifter allowing it to sit on the higher edge of it. End result is the distance between the cam lobe and rocker arm grows about 1/4" not factoring in the shorter straight distance between the ends of the push rod.

Now think what kind of damage you would have if you essentially replaced a hydraulic lifter with a solid lifter, then added 1/4" to the length of the push rod. I replaced a 6.0L engine with tha exact senario because the rocker arm actually broke when the valve got slapped by the piston caused by hanging out when the push rod "grew"

Ok. I will give you that the push rod with a little slippery oily ball on one end can balance on a surface that is less then 1/16" wide. So for this ball to end up balancing on this ledge the push rode would have to bend enough to get, per your measurement, 1/4" shorter. And if it got 1/4" shorter but balanced the edge 1/4" higher then the end result should be same as stock. Truck should run perfectly normal. Unless the push rods strength being bent is not enough to overcome the valve spring load and thus not open the valve.

BFT · Jan 23, 2012

Are you ***ing retarded?... If the ball catches the lip of the rocker arm it compresses the spring/springs opening the valve.

lubeowner · Jan 23, 2012

So how did push rod lose enough force to get unseated in the rocker arm?

BFT · Jan 23, 2012

Because its not straight. When something is straight and goes up and down its has it's set path. Now bend it and let it go up and down and see what it does

madman1234509 · Jan 23, 2012

BFT said:
Are you ***ing retarded?... If the ball catches the lip of the rocker arm it compresses the spring/springs opening the valve.

I dont think this comment is necessary... Especially with a respected companies banner being represented in your signature. This is a simple debate/converstation and there is no need for that.

Dzchey21 · Jan 23, 2012

Almost all pushrods that I have seen bent are a resulting damage not a cause of a major failure unless the pushrod ends up where it can get caught in other moving parts or hold something its not supposed to.

For the record I have seen a bent pushrod wedge between the rocker and the block with the valve open and cause issues but that was only 1 time on a cat engine. Generally when you pull a valve cover and find a bent pushrod your next step is to find the dropped valve seat or valve that caused the valve to stay open with the piston a top dead.

Looking at erics damage it does look like the piston failed first. Not sure why the spring broke but it did look like secondary damage to me.

BFT · Jan 23, 2012

madman1234509 said:
I dont think this comment is necessary... Especially with a respected companies banner being represented in your signature. This is a simple debate/converstation and there is no need for that.

What does my sig have anything to do with what I said? I am held accountable for my own actions and plus I'm staying on subject... Derail over

lubeowner · Jan 23, 2012

BFT said:
Because its not straight. When something is straight and goes up and down its has it's set path. Now bend it and let it go up and down and see what it does

Stand a straight push rod and a bent one up on a table which one will be taller?

BFT · Jan 23, 2012

Get off the whole length thing. If you don't believe that a bent push rod can drop or float a valve then I'm talking to a wall.

Erikclaw · Jan 23, 2012

If it is bent it does not follow the path that it is suppose to. It can start wondering around because of its curvature and then pushes on rockers etc at a point it was not designed to. Like the lip, there for pushes the rocker higher since it is not seated with the "little oily ball thing" in the cup.