Topic: Broken pushrod in a 289 K code - anyone ever see one?

[Bill]

Was driving the "K" home a while back and as soon as I slowed down I noticed that it was missing a cylinder. Lmped her home and the next day took off the valve cover and there laid a pushrod broken! I bent one several years ago but never saw a broken one and, really, don't know how that could happen. Anyone else ever seen a busted pushrod? I've attached a picture.

It damaged the top of the valve so we took off the heads to get them looked at and fixed. The rebuilder said he found washers under the vale springs (?), replaced about four valves, replaced the valve seats along with guides. Heads checked out well but it was weird the last time I had the heads resurfaced (over 10 years ago) somebody put in the washers for shims.

Bill Krieger

[RoyceP]

Yes, very common. Even when they were new. These engines were made to rev, hopefully you run the snot out of it like all its other owners have. That's what is fun about them!

Bent or broken pushrods can be caused by a multitude of things. Primary causes might be worn or misaligned parts that cause undue stress on the pushrod, which is meant to be the weak link in the chain. A bent pushrod is much better than a blown up piston and a rod through the side of the block.

The washers being used to shim a valve is not unusual, in fact it would have been common 40 years ago. It's not pretty looking but if done right it would not be a problem.

Too tight valve guides can cause valves to hit pistons and bent pushrods. Best practice would be to replace all the valves, valve springs and pushrods. If your rocker arms are suspect replace them too. All of those parts are relatively cheap compared to a 289 HP block. When assembling the engine particular attention must be paid to the pushrods and their alignment throughout their range of motion.

[Bill]

Thanks - bought three new pushrods and all the others appears straight with no dings or any flaws. Guys that redid the heads are competent. Pistons and cylinder walls check out okay so I am VERY lucky in that way.  May start a new topic on the "K" timing gear/chain/sprocket. Since the narrow ones are few and far between, going to replace mine with the standard one and dump the "hatchet". She ain't gonna be dragging anyone soon.

Thanks  again.

Bill

[jwc66k]

I've had four "K" codes (64 Fairlane Sports Coupe, 65 Mustang Fastback, 66 Mustang Fastback and a 66 Mustang Fastback GT) and the only engine problems I've had (two) were the valves themselves, no push rods. Most of the Shelby guy I've hung around with claim the same, valves. Transmissions and rear ends seem to be in second place.
JIm

[Bob Gaines]

Thanks - bought three new pushrods and all the others appears straight with no dings or any flaws. Guys that redid the heads are competent. Pistons and cylinder walls check out okay so I am VERY lucky in that way.  May start a new topic on the "K" timing gear/chain/sprocket. Since the narrow ones are few and far between, going to replace mine with the standard one and dump the "hatchet". She ain't gonna be dragging anyone soon.

Thanks  again.

Bill

Bill,  "going to replace mine with the standard one and dump the "hatchet". She ain't gonna be dragging anyone soon." If by these statments you are implying the hatchet head is for high RPM running then you mis understand. The hatchet head was a counterbalance so that the engine with the heavier rods could balance out within reasonaable specs in a mass produced assemblyline setting with out the benefit of the better but more labor intensive dynamic balancing like machine shops commonly do at a extra charge. Most racers dump the counter weight and have the the engine balanced to compensate for it not being there and switch out to a wider more durable under high performance conditions timing chain. Basically they dump the counter so that they CAN go dragging someone .Without it Less stuff to go wrong is what many racers say. If you already knew this then for those reading.

[jwc66k]

Bill,  "going to replace mine with the standard one and dump the "hatchet". She ain't gonna be dragging anyone soon." If by these statments you are implying the hatchet head is for high RPM running then you mis understand. The hatchet head was a counterbalance so that the engine with the heavier rods could balance out within reasonaable specs in a mass produced assemblyline setting with out the benefit of the better but more labor intensive dynamic balancing like machine shops commonly do at a extra charge. Most racers dump the counter weight and have the the engine balanced to compensate for it not being there and switch out to a wider more durable under high performance conditions timing chain. Basically they dump the counter so that they CAN go dragging someone .Without it Less stuff to go wrong is what many racers say. If you already knew this then for those reading.

Bingo!
Jim

[Texas Swede]

I have seen this problem with bent push rods happen a couple of times on HiPo's  over the years:
1: The rocker arm is worn and jumps sideways binding the push rod.
2: The stud at the bottom binds the rocker arm.

Personally I believe that when parts get worn and out of alignment s..t  happens.
Texad Swede

[Bossbill]

You don't mean REAL washers, do you?

Any decent valve job will include shimming valve springs with "shims" specifically designed for adjusting valve springs in order to get even spring pressure. They come in various thicknesses and diameters.

Even new springs are not perfectly matched at equivalent installed valve heights.  Basically, you measure the spring pressure at each valve using special tools, find any spring measuring a bit low and install a shim under that valve spring to slightly increase its pressure to match the others. Essentially blueprinting your spring pressure.

Shims usually have writing on them to denotes size and thickness, but not always.