after valve adjustment knock

GMR911 · 08-04-2006, 06:50 PM

Hi, just adjusted my valves today on my 911. Have done it numerous times before without issues. However, when I started it up, I hear a knock from the 4-6 cyl bank, seems to be more pronounced on the intake side than exhaust. I usually adjust the valves so there is a slight drag on the blade. Could I have gotten one too loose, or did some dirt get in there? I also change the spark plugs this past Wednesday. Any ideas before I take the valve covers off again and re-check or re-adjust the valves. Thanks Jerry

ianc · 08-04-2006, 10:57 PM

Not much to do but pull the covers off and try again. It's not that bad. Try to isolate the noise to a particular cylinder before doing so. Good luck,

ianc

gerard vaglio · 08-05-2006, 01:11 AM

Take off the top valve cover first, if your lucky you'll get the noisy one and be done!

If that doesn't work jack up the side of the car you'll be working on before you take off the bottom valve cover to let the oil run to the other side of the engine.

Now you won't even have to empty the oil to do the three exhaust valves on that side. This trick will save you a lot of time.

Oh, one more thing, sometimes an exhaust leak can sound a lot like a noisy valve. Look at where the exhaust bolts up to the engine for any signs of carbon. If one of those little gaskets fails just a little you'll swear it's a valve tapping.

I know I did.

Good luck, let us know what happens.

livi · 08-05-2006, 01:23 AM

You describe the sound as knocking - not ticking. Spontaneously it does not sound like a loose valve.

GMR911 · 08-05-2006, 05:12 AM

Thanks for the responses. The noise I am hearing sound like a knock coming from the the valve train, more so on the top. The funny thing is that is was not there previously to adjusting the valves and changing the spark plugs. I am thinking that I may have got some dirt or debris in one of the valves possibly or just adjusted one of the valves too loose. If I got some dirt in there how would you clean it out say if it was caught in a valve. I would think it would get burned up quickly. Sunday AM I am going to reset the valves again, anything else I shoud look for? Gerrard good point on lifting that side of car, may save me a couple qts of fresh oil. Also I just changed the oil and there was no visable metal filings on either the sump or tank plugs so I don't think this is a rod knock. Thanks again Jerry

Nine9six · Nine9six's Garage

Quote:

Originally posted by livi
You describe the sound as knocking - not ticking. Spontaneously it does not sound like a loose valve.

I agree...A loose valve will tick, and certainly would not be described as a knock. You may have other issues.

Nine9six · Nine9six's Garage

Quote:

Originally posted by GMR911
Thanks for the responses. The noise I am hearing sound like a knock coming from the the valve train, more so on the top. The funny thing is that is was not there previously to adjusting the valves and changing the spark plugs. I am thinking that I may have got some dirt or debris in one of the valves possibly or just adjusted one of the valves too loose. If I got some dirt in there how would you clean it out say if it was caught in a valve. I would think it would get burned up quickly. Sunday AM I am going to reset the valves again, anything else I shoud look for? Gerrard good point on lifting that side of car, may save me a couple qts of fresh oil. Also I just changed the oil and there was no visable metal filings on either the sump or tank plugs so I don't think this is a rod knock. Thanks again Jerry

Jerry,
Sorry I dont have a recommendation for you, but from what you describe above, I dont see anything that would create a knock.
Does the car idle smoothly, or does it run rough? At slightly off idle, can you still hear the knock? Have you tried pulling and reseating your plug wires?

GMR911 · 08-05-2006, 03:26 PM

Runs very smooth, idles nice. Yes you can still here the knock as you increase the RPMs. Pulled the plugs today and everything looks good with them. Sunday I am going to readjust the valves on the 4-6 cyl side, see if this helps, Jerry

Pasman · 03-07-2016, 07:29 AM

Just adjusted my valves on my 964 and have the what
sounds like the same issue. Almost a cracking noise when
engine is revved that turns into a knock when engine is
warmed up. Engine runs fine otherwise. What happened
with your issue many years ago, any resolution?
Thanks from a former Utican...

Guardsred911 · 03-08-2016, 04:04 PM

I had similar issues on my '80 sc. I went thru all the valves again and had a couple that were shockingly sloppy. I am not even sure what happened the first time but when I redid it, no issues.