dfinnegan

I'm in the midst of a valve adjustment and am poking around as I'm trying to track down a "hammering" type sound from the engine that's been there since I purchased the car about 5+ years ago.

It's not a "ticking" sound like a loose valve. It's more like a miniature ball-peen hammer on metal type sound. In fact, very much like the sound heard in the video link below!

I believe it to be in time with the valve train, as opposed to the crank, and definitely not wheel, gear, transmission, or speed related.

When I grab a rocker arm that is unloaded I find that I can move it side to side along the shaft; as opposed to against the valve stem. It makes a loud bang when it hits either side of its travel. When I move it back and forth quickly it begins to sound very much like the sound I hear when the engine is running under load; not so much when coasting, but under acceleration.

Should the rocker arms have this much freeplay?

This seems a bit excessive to me.

Link to video

Rocket Rob

KaiB

OK, I'll bite Rob (too tired to research)....

Why the popcorn?

Rocket Rob

Why the popcorn? I don't know the answer but am curious to learn the answer. The popcorn icon shows that I'm watching the thread but not participating. Picture someone eating popcorn while watching a movie. This icon is one of the standard RL icons.

KaiB

me too, me too.

I thought the popcorn icon represtnetd the upcoming theater...silly me.

tbennett017

Wow, that does seem pretty loose sounding. I have a similar sound that happens once in a while at startup and it goes away within 1-2 seconds.

I too, shall throw the popcorn.

tbennett017

Popcorn can also happen in the "What oil are you using on your Under-Tray" kind of thread...

KaiB

I got to thinking about this; every engine I've been into and remember allowed at least some sideways movement of the rocker arms - I cannot say this about Porsche heads, but the setup is essentially the same.

To back this up, I searched and the first hit was over at the Pelican forums - verification of the allowed sideways motion.

dfinnegan

Do you have a link?

KaiB

Hey, this am, this is what popped up first.

http://forums.pelicanparts.com/porsc...-movement.html

I found this interesting.

http://forums.pelicanparts.com/911-e...questions.html

This one vague.

http://forums.pelicanparts.com/911-e...questions.html

And this one quite specific.

http://forums.pelicanparts.com/bmw-r...-question.html

I do know for a fact on the older Triumphs (3,4) that lateral movement was normal.

bmohr

I can concur that I have this same movement in my engine as I just did a valve adjustment (first one) a few weeks back. The reason the movement stood out to me, is because It gave the impression of valves that was at TDC...made that similar amount of movement...only side to side instead of vertical.

elbeee964

...Sounds normal to me.

But 'sounds' don't tell the whole story.
How many inches lateral throw (total) is that?
Sitting here, I'm thinking that, oh, 0.05" lateral travel wouldn't 'blow my hair back none'.
But I haven't delved into the shop guide minutiae to get that number.
It's only what I recall seeing max. magnitude-wise when I last laid under Red.

dfinnegan

Lonnie: I didn't measure the lateral travel; though, I could easily have done so, and now wish I had! However, as a total swag I'd guesstimate something like 0.020"; maybe 3-5x the valve lash.

KaiB: Thanks for the links. I went over to Pelican and tried a couple of searches, but came up empty. Must have been user-error, some how. Interesting reads.

All of the rocker arms do move somewhat side to side. It seems like some move more than others; if only perceptively.

In the end I'm really after the unpleasant sound coming from my engine. It's always sounded a bit like $$$ to me and makes me nervous. It's been there since I bought the car back in '05 and has been noticed by a couple of folks, though no one has commented on a source. One shop said it sounded like the valves were very much out of adjustment. They were not.

I'll try and post a video clip of the sound the engine makes once I'm back on the road (not quite finished buttoning up the tin and mufflers), but it is a bit difficult to hear on a recording with all of the background noise the road and engine make. I've been researching noise analysis software lately in hopes that will help me isolate the sound.

Sure wish I had a neighbour, or friend close by, with a "Porsche ear" who could give it a listen.

I'll post again when I have more data.

Thanks for the input.

Cheers,
Dave

JasonAndreas

The numbers I have for axial play are (and I've never measured so I'm not even sure if these are correct);

0.100 (0.0079") - 0.350mm (0.0138")

and the wear limit is; 0.50mm (0.02").

dfinnegan

Jason, thank you.

Do you know what the "wear" in this case is? Is this actually wear on the sides of the cam tower casting where the rocker arms touch?

And, do you know if nearing the wear limits would cause noise?

Also, does anyone know if it's possible to have uneven wear on the cam, itself, such that the rocker arm is pushed from side to side as the cam rotates; which would be a possible explanation for the noise I'm hearing?

Isn't the issue on oil zddp levels all about cam wear? . . .

Thanks, again,
Dave