20 mile engine; is this a rod knock?

[nsracing]

Clay for what? You can check valve-to-piston clearance without it.

Either that valve got bent, inhaled something or the seat just cocked itself in there.

At any rate, at least take that topend off.

Are those forged rockers?

[Sigurd]

Yes, the rockers are forged. Scat 1.25s. The good ones.

There is plenty of oil in there. It drained out when I pulled the valve covers off. All that green stuff is oil (Brad Penn).

There was no clay, but there was a micrometer. There was plenty of valve-to-piston clearance.

I need to fix an oil leak and reseal some of the pushrod tubes anyway, so dropping the engine won't be such a big deal. Hopefully I can get away with just getting that one valve/guide/seat repaired.

[Jimmy111]

If the piston hit the valve it is usually the intake valve. But it is also possible it could be a dropped valve seat. I dont think that you cooked the head after just a short time. But you will find out soon.

[Sigurd]

I have 0.520" of lift on the intakes due to the Scat rockers being a little larger than 1.25. I did check the piston to valve clearance and it was about 1/8". It wasn't overheated. It ran hot for those few miles, with oil getting to about 215F, but I attribute that to tuning. Idle CHT is 250F and the highest it got was 350F. The knock started suddenly, barely audible, but got louder and louder.....while it was idling.

[miniman82]

You might get lucky, and only have to deal with a siezed guide. That usually happens to the exhaust valve on air cooled engines, though.
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[Sigurd]

Tore it down today. The pistons are a little oily. I also found oil in the intake ports.

Here you can clearly see the valve is stuck.

The combustion chambers. Plug #3 is white, and plug #4 is normal brown. Perhaps #3 ran a little lean.

I also noticed that when I took out the pushrods and stood them on end, oil poured out of all of them except #3 intake, which is the valve in question. It looks like it galled and seized in the guide. How are the valve stems supposed to be lubricated? Splash off from rockers? Did I drop a lifter and lose oil somewhere?

[miniman82]

I doubt it's an oiling issue, most likely the guide was too tight when the heads were machined. What usually happens is unscrupulous machine shops will install the guides, but never ream them to finished size. Result is a frozen valve. That's why I always tear down every head I use, even new ones. You never really know what's been done. After I inspect, I do my own lapping job, since that's seldom done by part sellers either. Unfortunately, 'off the shelf' parts are rarely 'finished' parts with this hobby.
The pushrod is empty because when the valve got stuck, there was nothing to keep oil in the pushrod (no spring pressure), so it all leaked out. No other reason than that.

If I were you, I'd see if you can get that spring are retainer off. See if you can coax the valve back out of the guide, and it might be possible to clean up the guide at a machine shop. Might as well look at all of them while you're at it....
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Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747

[Sigurd]

Thanks for the help. My local dude out here is back on Monday. I'll get the spring compressor and take a look.

[Matthew]

It will be easier to take apart if you can get that valve to close first. I would shoot some blaster at the guide from both sides and then gently tap the valve head with the but end of a wooden hammer handle. It will probably move a bit and then snap back closed.
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[Sigurd]

That did it. Thanks, Matthew. Miniman, these were not 'parts seller' heads. They definitely got worked over. I too, did some valve lapping of my own. I just wasn't aware that the guides could do that. What is the typical spec for valve-in-guide play?

[miniman82]

I don't know the spec anymore, I used to. I do it by feel now, same as the flywheel shims. First I stick the valve in it's guide, and let it drop closed by gravity. If it hangs up anywhere, it's not right and need to be cleaned up some more. Then with the valve all the way in and resting just above the seat, I should just be able to feel the movement, but not be able to see it. This is dry of course, no oil. Wiggle in a few different directions, since guides never wear evenly.
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Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747

[Sigurd]

I took both heads into the local shop last week. Hopefully they'll be done soon. New parts and a little more port work. Changing a few other things too; fixing the uneven deck on the case , fixing the uneven cylinders resulting from compensating for the uneven deck height , fixing the mismatched chamber volumes , bumping it up to 9:1 .