Valves tight ,, why?

Sinking valveseats?

J.

Did you check them while the engine was cold? How often do you check them?

as I understand the Muir's book. if you adjust them above 122 degrees F. you set them too tight. right? as it was I reset them and the compression reading came back to match cylinders 3 & 4. 125 or so. Wish me Luck OK?

LUCK! ;-)

You should be fine. BTW I usually check the torque of the lower cylinder head nuts before I adjust valves. I think the Muir book recommends that.

I concur -- loose heads would cause strange problem like this. Now, if the heads are loose you may have other problems. If the engine was running hot for a long drive, they would do it.

-Steve Ballantyne

Valves and valve seats wear. As they wear, the valve clearance goes down, so it's normal for valves to tighten up at some rate. If this is happening quickly, then something unusual may be going on, but "quickly" is subjective.

I find that I have to adjust 2-3 valves just a bit every 3000 miles, but they should never be at zero clearance in that time unless you're running the engine really hard or really hot.

BTW, if you have head studs coming loose, that will show up as loose valve clearance, not tight. And, yes, you should always adjust the valves with the engine at room temp.

----------------------------------------------- Jim Adney snipped-for-privacy@vwtype3.org Madison, WI 53711 USA

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I checked them today after sitting in 48 degrees over night. Drove 30 miles since the "correction" now they are fine.

thanks, group for the suggestions.

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It's time for a valve job.

In the VW valve train, wear accumulates at the interface between the cam and the cam-follower, between the cam-follower and the push-rod, between the push-rod and the rocker-arm, between the rocker arm and the rocker-arm shaft, and finally between the adjusting screw and tip of the valve stem. This accumulation of wear is dealt with by the adjusting screw. After about five adjustments the face of the adjusting screw will become faceted and the adjusting screw must be replaced. The accumulation of wear on the rocker-arm shaft appears as galling on the side of the shaft nearest the head. Standard procedure is to dismantle the rockker-arm shaft and reverse it, presenting an un-worn surface to the rocker arms.

You will note that in each of the above cases the accumulation of wear results in the adjustment becoming WIDER.

The ONLY time the adjustment can become SMALLER is when the valve stretches OR the valve seat is driven deeper into the head.

Both of these cases begin as heat-related phenomena, aided by hot-rod conventional wisdom that sez bigger valves and stronger springs -- are inherently better. In fact, the larger the diameter of the valve, the hotter it is going to run since its amount of heat-transfer surface is now proportionally small than for a smaller valve.

In the same manner, when the valve spring(s) are stronger than stock their excessive tension promotes 'necking' or stretching of the valve.

It is also worth mentioning that the use of larger valves and stronger springs is a technique used primarily in LIQUID-COOLED engines, where cylinder head temperatures are typically less than 200 degrees Fahrenheit. Apply that same technique to an air-cooled engine having CHT's as high as 450 degrees and you have virtually guaranteed stretched valves and failed valve seats.

-R.S.Hoover

Regarding 'hot rod' engines with larger valves, Bob, would you say this increased heat is a side effect that's bound to happen, as the larger springs generally complement hotter cams in order to prevent valve float?