 Why do valves need adjusting?, What's behind it all? |
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| kpfoten |
 Nov 25 2008, 01:22 PM
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#1
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Member  Group: Members Posts: 220 Joined: 15-April 08 From: Escanaba, MI Member No.: 8,927 Region Association: None  |
I'm a relative newbie when it comes to engine rebuilding, the physics, mechanics, etc, but I'm fascinated by it all and have been reading up on how it all works... I've done my share of valve adjustments, but the thought came to mind--why do we adjust valves? Is it a combination of heat and wear that causes them to need adjusting? Does spring fatigue have something to do with it?? |
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| 749142 |
Nov 25 2008, 01:28 PM
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#2
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Member Group: Members Posts: 254 Joined: 8-January 08 From: Bakersfield, Ca Member No.: 8,545 |
Its a combination of heat and wear mainly, the valve stem and tappet obiously wear, but the valve wears into the valves seat, and over the period of about 3,000miles the valve and valve seat where enough to remove your clearance, or your tappet and valve stem wear faster and then theres too much clearance
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| ericread |
Nov 25 2008, 02:13 PM
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#3
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The Viper Blue 914 Group: Members Posts: 2,177 Joined: 7-December 07 From: Irvine, CA (The OC) Member No.: 8,432 Region Association: Southern California |
Accordint to Auto Atlanta:
"Proper valve adjustment is critical to proper engine operation. Since the 914 engine is air cooled, it operates in a much broader temperature range than a water cooled car, resulting in more extreme expansion and contraction. This movement necessitates periodic valve adjustment." Eric Read |
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| kpfoten |
Nov 25 2008, 02:39 PM
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#4
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Member Group: Members Posts: 220 Joined: 15-April 08 From: Escanaba, MI Member No.: 8,927 Region Association: None |
Thanks!
I would assume that air cooled motors (even though with valves regularly adjusted) need the heads re-done sooner over time? |
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| Cap'n Krusty |
Nov 25 2008, 07:36 PM
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#5
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
QUOTE(kpfoten @ Nov 25 2008, 12:39 PM)  Thanks! I would assume that air cooled motors (even though with valves regularly adjusted) need the heads re-done sooner over time? Not particularly. BTW, spring fatigue has come up before, and it's not a possible answer, because the valve is a fixed length, the spring retainer is in a fixed location, and any tension at all will cause the valve to be fully closed at rest. Note I said "closed", not "sealed". The Cap'n |
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| VaccaRabite |
Nov 25 2008, 08:28 PM
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#6
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En Garde! Group: Admin Posts: 13,442 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
There is a brilliant B&W video on Youtube about VW T1 valve adjustments, and why they are important. I think it was from a VW tech school in the 60s. I'm going to go look for it, and if I can it will post it up. Its fun to watch old movies, but this one really cleared up a lot of questions for me when I first started getting curious.
Zach |
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| VaccaRabite |
Nov 25 2008, 08:30 PM
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#7
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En Garde! Group: Admin Posts: 13,442 Joined: 15-December 03 From: Dallastown, PA Member No.: 1,435 Region Association: MidAtlantic Region |
Sorry, not B&W, but still old and good. here is part 1:
http://www.youtube.com/watch?v=EpH7VftH3_I Here is part two: http://www.youtube.com/watch?v=vQ9ccGXtZL0 You should watch, its good stuff. Zach |
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| kpfoten |
Nov 25 2008, 10:05 PM
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#8
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Member Group: Members Posts: 220 Joined: 15-April 08 From: Escanaba, MI Member No.: 8,927 Region Association: None |
Thanks! Youtube is great for a lot of rebuild stuff. There's some guy in New Jersey that has good (Type IV Beetle?) rebuild video, and then the stuff from Costa Mesa R&D is really something else--I'm hooked on machining videos right now. I really wish I knew more about this stuff when I was younger--it may have influenced a career path... (IMG:style_emoticons/default/smile.gif)
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