[AT] [External] Re: Valve Seat Inserts

Fri Dec 4 04:55:34 PST 2020

The hardened seat installation was more needed for high RPM engines with high compression.  That certainly does not apply to old 2 cylinder John Deere engines; low compression in comparison, as well as low RPM made to run on cheap fuels.  I have had to get the machine shop to put valve seats in two old Deeres; one was an LA which has a flat head and where the seats are in the block; it had been overhauled several times; countless hours of abuse by a couple of previous owners; and the engine was so loose it would build up compression in the pan and blow the breather cap 50 feet in the air.  It needed new valve seat inserts to make it run again.  The other was an MT where the head was pretty destroyed but salvageable.  It had sentimental value as it was worn out when I purchased it many years ago. My father in law got scared once bush hogging with an old B with a hand clutch.  I was overseas in the Army, and when I got back to the US I bought the MT because it had a foot clutch and he was taking care of the farm and the fields in the soil conservation program had to be mowed.  That poor thing bush hogged through material as tall as the tractor, and he literally wore it out.  I restored it last year, have way too much money in it, but it will stay in the family.  

Dave Gerber 

Ohio

From: AT <at-bounces at lists.antique-tractor.com> On Behalf Of Jim Becker
Sent: Thursday, December 3, 2020 11:36 PM
To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com>
Subject: Re: [AT] [External] Re: Valve Seat Inserts

As far as I could see, the whole hardened valve seat problem was a lot of Chicken Little.  Back when most of these old tractors (and old cars) were made, regular gas had little to no lead in it anyway.  Tractors in particular were designed to run on the lowest octane gas commonly available.  Many just used valve seats ground straight into the cast iron and ran for decades.  The biggest exception was probably the LP heads that came with hardened seats made for some engines.  As leaded gas started getting harder to find, machine shops all over the country were cutting out perfectly good valve seats and sticking in replacement seats.  Even if the worst fears happened and there was excessive seat wear, the fix would still just be to install valve seats.  Worst case is the same as the preemptive treatment!

Was a waste of effort.

Jim Becker

From: Jason 

Sent: Thursday, December 03, 2020 8:24 AM

To: Antique Tractor Email Discussion Group 

Subject: Re: [AT] [External] Re: Valve Seat Inserts

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. 

Very old low compression motors often don't need this done because their combustion temperatures are so low.

Jason

On Thu, Dec 3, 2020, 8:08 AM Gunnells, Brad R <brad-gunnells at uiowa.edu <mailto:brad-gunnells at uiowa.edu> > wrote:

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.

Brad

On 12/3/20, 12:57 AM, "AT on behalf of Dean VP" <at-bounces at lists.antique-tractor.com on behalf of deanvp at att.net <mailto:at-bounces at lists.antique-tractor.com%20on%20behalf%20of%20deanvp at att.net> > wrote:

    Steve,

    AHA,, I completely overlooked they were two different parts. Now the lights
    go on.  Now I understand. The valve seat might be damaged but the guide may
    still be good or vice versa.   As I recall that was more of a problem in the
    40's and 50's than it is now.

    Dean VP
    Apache Junction, AZ

    -----Original Message-----
    From: AT <at-bounces at lists.antique-tractor.com <mailto:at-bounces at lists.antique-tractor.com> > On Behalf Of Steve W.
    Sent: Wednesday, December 2, 2020 11:38 PM
    To: Antique Tractor Email Discussion Group <at at lists.antique-tractor.com <mailto:at at lists.antique-tractor.com> >
    Subject: Re: [AT] Valve Seat Inserts

    Dean VP wrote:
    > Found a term in this company's price list that rings some memories
    > but really hazy ones.    Could someone explain when and why "Valve
    > Seat Inserts"  are used rather than replacing the whole valve guide?
    > Yes, they are a little less expensive but not that much  Please 
    > refresh my hazy memory from the 50's.
    > 
    > 
    > 
    > Dean VP
    > 

    Different parts. The valve guide holds the valve stem and keeps it in
    position. The valve seat is the ground part of the port in the head that the
    valve face seals against. The reason for the inserts are a few, one is that
    you might have a head with damaged or eroded seats and the valves won't
    seal. You machine out the worn/damaged area, press in the inserts and either
    peen the edge or more commonly you bore the area for the seat with a step so
    the seat locks into the head, to install you freeze the insert and heat up
    the head. Then the two parts lock together as the temperatures normalize.
    Have done both and prefer the second option.

    --
    Steve W.
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