Re: Sodium and Silicone and Torsen

["Fred Munro" <munrof@isys.ca>]

-----Original Message-----
From: Mike Miller <JoMi@email.msn.com>
To: munrof <munrof>
Cc: quattro <quattro@coimbra.ans.net>
Date: Tuesday, June 02, 1998 11:21 AM
Subject: Re: Sodium and Silicone and Torsen


>
>-----Original Message-----
>From: Janet Scruggs <scruggs@mbay.net>
>
>
>
>>I understand the lead
>>deposits coat the valve stems to form a rather tight 'running fit' between
>>the stem and valve guide which further promotes heat transfer from the
>>valve to the head.
>
>
>My understanding is that the lead lubricated the valve seats. Thats why you
>have to put in hardened valve seats when you switch from leaded to unleaded
>gas. Don't know how the lead would have gotten up to the valve stem/guide.
>
>mike miller
>91 200q
>
Ditto my understanding. Without the lead on the valve seat (the lead
deposits on the relatively cool valve seat surface), when the valve closes
the high points "microweld" to the seat. When the valve re-opens, it takes
minute pieces of the seat with it. This gradually erodes the valve seat.
Hardened seats do not have this problem.

Fred Munro
'91 200q  253k km