<div dir="auto">Yes. Lead in addition to be an antiknock agent also coated the valve seats to prevent wear on valve seats. Only the exhaust seats need to be replaced.<div dir="auto"><br></div><div dir="auto">Very old low compression motors often don't need this done because their combustion temperatures are so low.</div><div dir="auto"><br></div><div dir="auto">Jason</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Dec 3, 2020, 8:08 AM Gunnells, Brad R <<a href="mailto:brad-gunnells@uiowa.edu">brad-gunnells@uiowa.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Wasn't there something also with the change from leaded to unleaded fuels? For some reason I thought manufacturers started putting harder valve seats in later model engines due to the limiting of lead. I could be way off here but I thought I'd heard about that back in my dirt track racing days.<br>
<br>
Brad<br>
<br>
On 12/3/20, 12:57 AM, "AT on behalf of Dean VP" <<a href="mailto:at-bounces@lists.antique-tractor.com" target="_blank" rel="noreferrer">at-bounces@lists.antique-tractor.com</a> on behalf of <a href="mailto:deanvp@att.net" target="_blank" rel="noreferrer">deanvp@att.net</a>> wrote:<br>
<br>
Steve,<br>
<br>
AHA,, I completely overlooked they were two different parts. Now the lights<br>
go on. Now I understand. The valve seat might be damaged but the guide may<br>
still be good or vice versa. As I recall that was more of a problem in the<br>
40's and 50's than it is now.<br>
<br>
Dean VP<br>
Apache Junction, AZ<br>
<br>
-----Original Message-----<br>
From: AT <<a href="mailto:at-bounces@lists.antique-tractor.com" target="_blank" rel="noreferrer">at-bounces@lists.antique-tractor.com</a>> On Behalf Of Steve W.<br>
Sent: Wednesday, December 2, 2020 11:38 PM<br>
To: Antique Tractor Email Discussion Group <<a href="mailto:at@lists.antique-tractor.com" target="_blank" rel="noreferrer">at@lists.antique-tractor.com</a>><br>
Subject: Re: [AT] Valve Seat Inserts<br>
<br>
Dean VP wrote:<br>
> Found a term in this company's price list that rings some memories<br>
> but really hazy ones. Could someone explain when and why "Valve<br>
> Seat Inserts" are used rather than replacing the whole valve guide?<br>
> Yes, they are a little less expensive but not that much Please <br>
> refresh my hazy memory from the 50's.<br>
> <br>
> <br>
> <br>
> Dean VP<br>
> <br>
<br>
Different parts. The valve guide holds the valve stem and keeps it in<br>
position. The valve seat is the ground part of the port in the head that the<br>
valve face seals against. The reason for the inserts are a few, one is that<br>
you might have a head with damaged or eroded seats and the valves won't<br>
seal. You machine out the worn/damaged area, press in the inserts and either<br>
peen the edge or more commonly you bore the area for the seat with a step so<br>
the seat locks into the head, to install you freeze the insert and heat up<br>
the head. Then the two parts lock together as the temperatures normalize.<br>
Have done both and prefer the second option.<br>
<br>
--<br>
Steve W.<br>
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