As valve adjustment "ages"

S785Carrera · 10-19-2005, 07:15 AM

I have about 15,000 miles on my 3.2 since my last valve adjustment. It runs great and the valves are relatively quiet.
The question is, as the valves become "mis -adjusted" or "age"
Do they tend to get looser / louder or quiet / tight ? If they get
loose / louder over time, could you just wait till they got a little loud before adjusting them?

Thanks,
Mike

livi · 10-19-2005, 07:27 AM

They could likely go either way. Problem being that its impossible to hear if say one or two valves are going the "wrong" way - getting tighter - for all the noise of the rest thats getting looser..

I would think.... But hey, I am a newbie !

If you have 15k on them its probably about time for an adjust.

thunderdenton · 10-19-2005, 07:30 AM

What he said.

I will add this. It is much more dangerouse if the valves are too tight. And if they are too tight these valves would be quite! Adjust them at 15000 to be safe.

S785Carrera · 10-19-2005, 09:02 AM

Thanks-

So some will get tighter and others will get loose? I would think from a mechanical standpoint that they would tend to either get loose or tight,
but not both. But then again I have not done a valve adjustment myself yet. Is there anyone that has a lot of valve adjustment experience that
can confirm that they some would get loose while others get tight?
What is the mechanical reason for the valves getting tight or loose with time / miles?

livi · 10-19-2005, 09:15 AM

You will get answers from the gurus I hope. But I guess most people in your corner are sound a sleep right now or about to rise and shine shortly.

I am surprised the two of you are up ! Must be very early in the morning over there ?

S785Carrera · 10-19-2005, 09:32 AM

Nope, 1:30 in the afternoon here. So the Gurus are awake hopefully !

livi · 10-19-2005, 09:39 AM

Oh oh - your right. Is that the time ? I should be sleeping !!

jet911 · 10-19-2005, 09:45 AM

I don't understand how a valve could get tighter (I suppose it is possible). I can understand how they can loosen up and get louder. At 15K do the adjustment. You need to check all valves and may only end up adjusting a couple or so. Just make sure you can get the feeler gauge back in after you adjust them. There sould be some resistence when pulling the blade out. Have fun!

thunderdenton · 10-19-2005, 09:48 AM

Most of the time they will get more lose.

If the heads become slightly loose this will make valves tight.

This can happen.

S785Carrera · 10-19-2005, 09:53 AM

In this case wouldn't you re-torque the head ?

William Miller · 10-19-2005, 09:57 AM

Good question on the valves! I'm responding just to see what happens.

thunderdenton · 10-19-2005, 10:29 AM

Quote:

Originally posted by S785Carrera
In this case wouldn't you re-torque the head ?

Exactly!

I will be a little more verbose (I was on my Blackberry earlier), so if I say something you know then just ignore it.

With the heating and cooling cycles your engine goes thru will affect your valve clearances. These valve clearances will generally get looser unless your heads need to be re-torqued.

If the heads need to be re-torqued you may also notice some popping sounds until the engine warms up (expanding the cylinders to close the distance between the heads). You may not hear this when they first start to get out of speck.

Adjusting your valves gives you an opportunity to know if you need to re-torque your heads.

If the valves are too tight then they will stay partially open creating a potential for the piston and the valve to collide.

KobaltBlau · 10-19-2005, 10:34 AM

Quote:

Originally posted by thunderdenton

If the valves are too tight then they will stay partially open creating a potential for the piston and the valve to collide.

Or the more imminent damger if the exhaust valve is too tight and doesn't contact the seat well is it gets "burned"

thunderdenton · 10-19-2005, 10:43 AM

Quote:

Originally posted by KobaltBlau
Or the more imminent damger if the exhaust valve is too tight and doesn't contact the seat well is it gets "burned"

For the mechanical reason for this (since it was asked earlier):

The heads act as a heat sink to move heat away from the valves. If the exhaust do not make good contact with the head they will get “burned”.

One of the reasons it is more “imminent” is most pistons now have a cut out that helps prevent valve piston collisions, or the shape of the piston helps prevent the collisions.

Flipseat · 10-19-2005, 11:19 AM

Quote:

Originally posted by S785Carrera
Thanks-

So some will get tighter and others will get loose? I would think from a mechanical standpoint that they would tend to either get loose or tight,
but not both. But then again I have not done a valve adjustment myself yet. Is there anyone that has a lot of valve adjustment experience that
can confirm that they some would get loose while others get tight?
What is the mechanical reason for the valves getting tight or loose with time / miles?

Valves can get tight and loose... not the same valve at the same time though. You may have some that are loose, and others that are tight. Valve adjustments are a key maintenance item that need to be done. If you drive too far on a tight valve you can burn one....and thats no good. Too loose is better than too tight. But, we're talking thousandths of an inch here, so don't get too crazy. You don't want a valve way too loose!

A valve will get loose because of wear on the valve train. A valve will get tight if a valve seat is sinking, or a valve is stretching. You can keep a log of your valve adjustments so you know whats happening over time. Just write down what cylinder, and what valve, and what the measurement was before the adjustment or simply if it was loose, tight, or ok.

On my air cooled VWs I check/adjust the valves at every oil change which is usually about 1500-2000 miles (no oil filter) and the recommended time to adjust/check them is 3K miles. Thats VW though...