Push Rod Rotation

[Green Bean]

Still trying to find the source of ticking engine noise, previously I had re-adjusted valve clearance. This morning I decided to see if I had a bent push rod by checking for rotation. All I can say is that they all appear to be rotating, albeit some much faster than others. Nothing jumped out to me as being dreadfully out of whack. As always, I'd sure appreciate any feedback on the source of the ticking. (Everything seems to run fine. Starts easy, not oil consumption). Thanks!

 

[Grayscale]

Worn rocker arm bushes. and rocker arm shaft?

 

[brian]

take a slow motion video

 

[B y r o n]

If you are worried about bent push rods then the only reliable check I know of is rolling them on a plate of glass.

 

[Mark Jennings]

The video is pretty cool….shows 2 things for the novice FJ40 owner, 1) don’t be afraid to run the engine with the valve cover off and 2) valve geometry in a working engine.

As far as your ticking, besides being an endearment of a mechanical valve train…a little clatter tells me you have a good valve adjustment. Believe me, I used to work for a VW dealership in the late 60’s and early 70’s, a ticking air cooled engine was a happy air cooled engine. A ticking FJ40 F and 2F is a happy FJ40.

However, on your FJ40, your adjustment may be a bit uneven….your pushrods turning at ‘light’ speed are a bit loose….example #1 exhaust. It’s twice as fast as the intake.

As far as worn rocker shafts….you can flip them over, there are oiling holes top and bottom….that way you have at least clean shaft supporting the rockers….

 

[franklin40]

sorry can't help you but that IS a cool video!!

 

[Its me shaneus]

Camshaft lobes are ground on a very slight taper. This is to promote the lifter to rotate as the cam lobe goes past underneath it. It causes the bottom of the lifter to wear evenly. The rotating lifter passes the rotation on to the pushrod.

 

[65swb45]

If you’re using a standard feeler gauge to measure valve clearance, keep in mind that the valve is narrower than the tip of the rocker arm, so over time, the tips get grooves that are deeper in the middle than the sides.

When I service a cylinder head, I look at the rocker tips, and if they are grooved, I dress them by hand.

 

[Grayscale]

With the rocker arm assembly on the bench, you'll find wear and the resulting clatter. Back when it was in service, there was a set amount of rotational rock that the rockers could move with the cam lobe lift, thermal expansion/contraction, and lash set during tune-up. Along comes oil formulas better suited for hydraulic-lifter-type valve set-ups, or, the engine was just from performing hard work. Now, the circular rocker shaft is looking kinda D-shaped, the face of the rocker is like what Mark - 65swb45 was describing, and there is probably also less cam, lifter, pushrod - it all wore away. With that wear, you get a step where the wear begins on the 'D' of the rocker shaft and bushing, and if you keep the rocker within that worn-out zone, no audible click with the rocker arm assembly, at least on the bench. However, when you adjust the length that the screw protrudes on the rocker arm, the rockers might have to rotate past the little worn-in step on the rocker shaft - hence the click.

Regardless, it must be like hammer-striking-force. When the engine is running, it goes from some lash and zero pressure on the valve stem face, to a force that can overcome the pressure of compressing the valve springs, back to a gap. A thin film of oil is the only cusion for wear and friction. I'd bet that they sounded kinda rough back when they were new.