Pelican Parts
Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help



Go Back   Pelican Parts Forums > 1- Porsche Technical Forums > 911 Engine Rebuilding Forum


Reply
 
LinkBack Thread Tools Rate Thread
Author
Thread Post New Thread    Reply
Banned from Pelican
 
snowman's Avatar
 
Join Date: Feb 2003
Location: So California
Posts: 3,787
Quote:
Originally posted by Mark McClure
I have been under the impression that lapping in valves is a way of reseating them in the seat. The more you lap the lower the valve is seated and the more the face is matched.

......
The valve seat, in the case of a 3 angle grind is say 0.050" wide, the valve face is approx 2 to 3 times as wide, eg 0.150" wide. Consequently there will be a ring of contact on the valve face that is 0.050" wide, usually near the outter third of the valve face. If the valves are lapped properly they will define a ring or groove that does not have any ridges inside of the contact area, but there will be a sharp step both on the top and bottom of the contact area. They will seal perfactly untill the temperature changes and like I stated before the vavle gets longer, the seat larger in diameter and you now have the contact surfaces sitting on top of one of these ridges. Valve manufacturers send out info on this to machine shops that include a good picture of what is happening

Last edited by snowman; 05-19-2005 at 01:59 PM..
Old 05-19-2005, 01:16 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #21 (permalink)
Banned from Pelican
 
snowman's Avatar
 
Join Date: Feb 2003
Location: So California
Posts: 3,787
The followin has been lifted from a repair manuel for a very late model engine. The info is typical of the entire industry for late model engines. Black, blue, green, even pink felt tip markers can be used instead of blue dye.



Last edited by snowman; 05-19-2005 at 02:16 PM..
Old 05-19-2005, 02:02 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #22 (permalink)
Registered User
 
Join Date: Apr 2005
Location: Co. Carlow, Ireland
Posts: 455
Thanks for posting this Jack - it all sounds like useful stuff, but why does it say that you can lap refaced valves but should never lap new valves "under any condition"? Is there something about the surface of new valves which would damage the seat if you tried to lap them?
__________________
Charles

'84 911 3.2

Last edited by CharlesJones; 05-19-2005 at 03:03 PM..
Old 05-19-2005, 02:26 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #23 (permalink)
Banned from Pelican
 
snowman's Avatar
 
Join Date: Feb 2003
Location: So California
Posts: 3,787
What I have read is that there is some kind of special coating on the face of new valves. Other thing I have heard is that new valves are so perfact and concentric that the only thing you can do to them is to make them worse.
Old 05-19-2005, 03:25 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #24 (permalink)
Registered User
 
Join Date: Jul 2002
Location: Canberra Australia
Posts: 440
Jack,

That all make sence now ........ I was missing the bit about the ridge above and below the contact area after AGRESSIVE lapping.

I am just about to tear into my engine and in a cost saving effort my first though was to lap the valves to make sure I had a good seal. I now think that I should have them cut. OK the price of the rebuild has just gone up.

Thanks for the good information!...........Cheers
Old 05-19-2005, 03:56 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #25 (permalink)
Banned from Pelican
 
snowman's Avatar
 
Join Date: Feb 2003
Location: So California
Posts: 3,787
An additonal note for those taking notes. THe specs for the angles, margins, and seat widths given are for valves that are approx 1" dia to 1.3" dia and for a particular engine. Do not use these specs for your engine, use your manufacturers specs for your year and model.
Old 05-19-2005, 09:09 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #26 (permalink)
 
Reply

Thread Tools
Rate This Thread
Rate This Thread:

 


All times are GMT -8. The time now is 06:54 AM.


 
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2018 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page
 

DTO Garage Plus vBulletin Plugins by Drive Thru Online, Inc.