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nsracing Samba Member
Joined: November 16, 2003 Posts: 9459 Location: NOVA
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Posted: Fri Aug 14, 2009 2:46 am Post subject: |
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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? |
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Sigurd Samba Member
Joined: April 18, 2006 Posts: 2639 Location: Rockford, IL
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Posted: Fri Aug 14, 2009 5:30 am Post subject: |
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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. |
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Jimmy111 Samba Member
Joined: October 05, 2006 Posts: 2643 Location: Wyoming
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Posted: Fri Aug 14, 2009 6:59 am Post subject: |
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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. |
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Sigurd Samba Member
Joined: April 18, 2006 Posts: 2639 Location: Rockford, IL
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Posted: Fri Aug 14, 2009 7:06 am Post subject: |
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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. |
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miniman82 Samba Swamp Donkey
Joined: March 22, 2005 Posts: 9515 Location: Southern Maryland
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Posted: Fri Aug 14, 2009 8:13 am Post subject: |
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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. _________________ Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747
Glenn wrote: |
satterley_sr wrote: |
I just wanted to bitch but I'm getting no sympathy. |
Welcome to the Samba. |
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Sigurd Samba Member
Joined: April 18, 2006 Posts: 2639 Location: Rockford, IL
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Posted: Sat Aug 15, 2009 10:57 am Post subject: |
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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? |
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miniman82 Samba Swamp Donkey
Joined: March 22, 2005 Posts: 9515 Location: Southern Maryland
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Posted: Sat Aug 15, 2009 12:25 pm Post subject: |
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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.... _________________ Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747
Glenn wrote: |
satterley_sr wrote: |
I just wanted to bitch but I'm getting no sympathy. |
Welcome to the Samba. |
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Sigurd Samba Member
Joined: April 18, 2006 Posts: 2639 Location: Rockford, IL
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Posted: Sat Aug 15, 2009 10:37 pm Post subject: |
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Thanks for the help. My local dude out here is back on Monday. I'll get the spring compressor and take a look. |
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Matthew Samba Member
Joined: January 29, 2004 Posts: 1760 Location: Eastern Tennessee
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Posted: Sun Aug 16, 2009 8:13 am Post subject: |
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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. _________________ 1965 Beetle sedan
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Sigurd Samba Member
Joined: April 18, 2006 Posts: 2639 Location: Rockford, IL
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Posted: Sun Aug 16, 2009 9:17 am Post subject: |
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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? |
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miniman82 Samba Swamp Donkey
Joined: March 22, 2005 Posts: 9515 Location: Southern Maryland
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Posted: Sun Aug 16, 2009 10:13 am Post subject: |
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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. _________________ Build thread: http://www.thesamba.com/vw/forum/viewtopic.php?t=212747
Glenn wrote: |
satterley_sr wrote: |
I just wanted to bitch but I'm getting no sympathy. |
Welcome to the Samba. |
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Sigurd Samba Member
Joined: April 18, 2006 Posts: 2639 Location: Rockford, IL
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Posted: Tue Aug 25, 2009 10:24 am Post subject: |
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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 . |
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