67 283 keeps bending pushrod
 

fellas,
I have a 67 283 and cylinder 7 the intake valve rocker slips off and bends the pushrod.
I installed a new lifter/pushrod then put the original rocker back on and when adjusting it if I barely tightened it it would want to slip off. I changed out another rocker and the same thing happened.
I tightened it just enough to take the tick away and took it for about a 15 mile spin, about 10 miles in I gave it a good shot and bam I got the lifter tick, came home pulled the cover and found the rocker off the valve with a bent pushrod.
The post on the head doesn’t seam bent
Any ideas?

Cheers
Brant

Re: 67 283 keeps bending pushrod
 

When you adjust the valve how many turns does it take to take up the lash? I'm thinking a possible broken spring. Check the tip of the valve for squareness also

Re: 67 283 keeps bending pushrod
 

After the lash was taken up if I tightened it up a typical 1/2 turn it would want to slip right off , if I took it 1/4 it wasn’t really square on the valve but enough to not slide off… until I hit about 4000 rpm

Re: 67 283 keeps bending pushrod
 

Is the top of the valve worn? It looks like it in the pic.

Re: 67 283 keeps bending pushrod
 

Looks like it to me also.

Re: 67 283 keeps bending pushrod
 

Things that can bend a push rod.
1. Spring coil binds
2. Valve retainer hits top of valve guide
3. Slot in rocker arm not long enough to allow full lift. (Rocker stops moving. Against rocker stud, not likely your problem)
4. Bent valve.
That hole in the head where the push rod goes, should be flat on each side. It is a guide for the Push rod to ride against. To keep the rocker on the top/ center of the valve stem tip. It could face or into your problem.....

Something is hitting something solid and stopping free valve train movement.

If your pickup is needed as a daily driver, you know that the 1/4 turn adjustment works at Lowe engine speeds, this would allow you to limp it around for a while, BUT could cause more damage...

Re: 67 283 keeps bending pushrod
 

Is the fuel fresh? Old gas can varnish the valve stems causing them to stick in the guides which in turn bends the pushrods.

Re: 67 283 keeps bending pushrod
 

A close-up pic of the top of the valve stem would be helpful. Push rod guide looks enlarged also. Possible worn cam lobe creating slop in rocker, damaging top of valve stem and misaligning push rod to wear guide.

My .02

Re: 67 283 keeps bending pushrod
 

Check to see if there's a slot worn in the side of the rocker arm stud. That will let the rocker to move sideways and slip off the pushrod. The mushroom look of the top of the valve indicates loose adjustment also.

Re: 67 283 keeps bending pushrod
 

Just a thought. Is it possible the press in stud is starting to back out of the head? Of course, it would start making a racket as it loosened up.

Re: 67 283 keeps bending pushrod
 

Good advice. Take a rubber mallet and bounce it on the valve stem. Make sure the stem is free to slide.

Re: 67 283 keeps bending pushrod
 

If the studs are all the same height and the valves are all adjusted the same, you should have approximately the same number of exposed threads above all the adjuster nuts.
If the exposed threads are different, this should help you find the problem.
Why did you change the lifter? Was this problem there before?

Re: 67 283 keeps bending pushrod
 

Hey guys thanks for all the input, turns out the valve was worn on a angle I guess due to a loose rocker? Wore over time ? Enough to make it slip off eventually . Had a couple options grind the valve stem flat again or slap on a newer vortec 350 style rocker with guides on either side… it’s a 289, not planning on breaking any land speed records. We will see how it holds up. Down the road it may be due for an overhaul, 61 000 original miles and it’s just a Sunday driver for now , the patina looks nice , I installed a tach, temp and oil pressure sensor

Re: 67 283 keeps bending pushrod
 

Should be a couple pictures

Re: 67 283 keeps bending pushrod
 

Welcome aboard .I'm glad you may have fixed it for now .(flipped pic) :)

Re: 67 283 keeps bending pushrod
 

That's a good, low buck and practical idea. Let us know how it works out.

Re: 67 283 keeps bending pushrod
 

Can’t help with the rocker issue but I love your color and the 3 on the tree ! I miss my 68 GMC with it…:metal:

Re: 67 283 keeps bending pushrod
 

Welcome to the Boards. Nice truck and looks vaguely familiar. Sorry for the valve grief so soon.

Re: 67 283 keeps bending pushrod
 

I had a 67 El Camino with a 327. It had 200,000 miles on it. The holes in the head that act as pushrod guides were worn and it started bending pushrods. The fix is getting steel pushrod guides like these:

https://www.amazon.com/Small-Block-C.../dp/B075NPHNPZ