#3 intake valve

[rasouth]

Any ideas why the #3 intake valve would be clattering on a '78?
The valve clearance is within specs, timing is correct, oil is fine, 20/50 wt oil with some Lucas oil additive to thicken it up, changed valve shim from 4.05 to 4.10 with no difference, valve cup is not out-of-round or heavily scored, cam lobes show very little signs of wear, oil pressure is around 38 at start -up and around 25-30 after warmed up.

[Daniel]

what kind of noise is that valve making a clicking type ? how did you determine # 3

[ventura ace]

Broken valve spring maybe? Excessive valve stem clearance??

Alvon

[So Cal Mark]

foreign object in the cylinder?

[Daniel]

if you have a broken inner valve spring it will start to float the valve around 6k RPM on these engines
causing a miss fire for that cylinder making a kind of poping noise if it was the outer spring not sure
what RPM range it would start to float cause i've never had one break on me but would be lower .

Also when the inner spring was broken on my engine i never heard any noise and drove fine till
it was past 6K RPM .

[rasouth]

I don't think it's the springs. I took apart the heads a while ago and springs were fine. I found which valve it was by using a stethoscope and had it confirmed by a VW mechanic who listened to the noise. The noise sounds as if the cam lobe is slapping the shim. The noise is not always constant, meaning that it starts after the car has run for about 2 minutes and sounds as if it "clacks" 7 to 8 times out of ten revolutions of the cam and only at an idle. Other than the noise the car runs good.

[Daniel]

can you video tape this with audio and upload to youtube ? then we can listen to it if so might be easy to tell you
more or less if it is normal or not if there is a problem might be able to help with that as well . Even with the shims
are within spec these engine tend to be a bit noisy it used to drive me nuts after adjusting the valves on one
of these then start it up every valve was adjusted correct to specs and still hear some ticking

[So Cal Mark]

you said the clearance was correct, but what is it set at? What is the condition of the lobe? You check clearance opposite of the lobe, so the cam could be going flat and still have proper clearance. I've seen lots of bad lobes on these engines

[rasouth]

The clearance was .43 before changing shim. Now it's at .48. The lobe looked okay; no chips or cracks on visual inspection. The last time I had the cams out I measured the lobe with a digital caliper, top to bottom, and all of the lobes were very close to each other, less than 1/32 difference between them.