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"Best"? exhaust valve guide material?

steve-l

Titanium
Joined
Mar 2, 2012
Location
Geilenkirchen, Germany
Okay fine there Zippy.....:icon_bs:
"There is absolutely no way"
Lovely how you are so "absolute" in your reprimanding me.
The requirements are 100% power for 5 minutes, and 75% for the duration of the flight.
Zippy? There is nothing I stated that is not true. I do not dispute those requirements. I will repeat that a type 1 VW motor is not up to those requirements. There are engines designed for that level of service and that VW motor is not.
 

michiganbuck

Diamond
Joined
Jun 28, 2012
Location
Mt Clemens, Michigan 48035
An airplane engine would have to use the authorized repair parts because they are the ones that have been tested and approved. They are likely a balance between the very best, and good enough to function for the number of hours between the regulated cycles/time between maintenance events.

Catastrophic failure can't be tolerated but would likely occur if the engine was taken off the maintenance events schedule, and just subject to continued use until components wore out.

Because of cost-based, and time-life selection the recommended ones may not be the very best. Using the engine outside of airplane use race car engine parts may be the better selection. A pro race engine rebuilder/designer might give the best advice
 
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Servicar rider

Cast Iron
Joined
Sep 6, 2008
Location
Coggon Iowa usa
I am basing my answer in what I know works in Harley engines. When the lead was removed from gas, Harleys started having all kinds of valve/guide problems especially sticking valves. The cure was found to be fine grained cast iron guides with nitrided stainless valves with valve guide seals.. The upside to this was tighter clearances and much longer life, like at least 4 times what it was previously! You see almost no valve stem or guide wear even with high miles. I would think a VW could benefit from this?
 
I found Thesamba, lots of machinists there with knowledge of machining VW engines.
With that information, i made tooling and a fixture

DSC_0052.JPGDSC_0085.JPGDSC_0079.JPGDSC_0088.JPGDSC_0094.JPG

I thought my engine guru was dodging me, after over a week of non-committal responses. He sent an email with enthusiasm for the project.. Valves and such were ordered mid-last week, hope to see them soon. Guide decisions are still up in the air until we meet to discuss this, and whether any OS dia are needed. One that was removed started spinning before the counterbore was as deep as i'd like; and it is discolored a little partway up the OD above the end that extends into the chamber. In pinch, though, the fixtures and tooling are now on hand if something conspires to force me to complete the heads here including boring for OS guides, or seats. I hope not. :)
 

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dian

Titanium
Joined
Feb 22, 2010
Location
ch
what valves did you opt for? ev4? ev8?

edit: "thesamba" is interessting. i used to hang out on "914world".
 
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stainless get the most votes, especially on the aircraft forums.
Apparently (as alluded to earlier this thread) for VW aero engines, valve jobs and valves are a 200 - 250 hour routine maintenance Item, and you just use them as consumables. It all seems cheap compared to Lycoming and Continental parts, but a regular (pun intended) nuisance. If these heads were not refreshed when the nikasil cylinders were removed and steel barrels installed & logged as "moteur neuf" then they are right on schedule with something around 300 hrs. I would hate to think they were fresh, have this much wear on the exhausts, and were new 33 hrs ago at that log entry.

Hard chrome stems get a lot of support, it's not uncommon for airplanes. But i went with plain. In some of my reading, it appears VW actually used to make sodium filled valves. I did not explore that.

As mentioned, i'll run this all by my engine guy who is also a pilot.

smt
 








 
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