| hardened exhaust valve seats [message #361063] |
Mon, 21 December 2020 14:44  |
rgogan
Messages: 82
Registered: February 2004
Location: Milwaukee, WI
Karma: 0
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I purchased a used J head from a 1975 Oldsmobile Cutlass 455. The rebuilder that I am using cannot tell if the exhaust seats were induction hardened during the original build. He can install hardened seats if I insist but he is concerned that can open up a can of worms. Any engine overheating or exhaust restriction will cause the seat to become undone in the head. This already happened to me in my air cooled Briggs and Stratton riding lawn tractor. Mice had built a nest under the air cooling baffles and the engine over heated and the hardened seats popped out. Tried some internet magic epoxy to rebed the seats but the fix lasted for only one trip around the lawn.
Does anyone know if GM was supplying J-heads with hardened exhaust valve seats in 1975 so I don't have to deal with this problem?
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| Re: [GMCnet] hardened exhaust valve seats [message #361064 is a reply to message #361063] |
Mon, 21 December 2020 15:13  |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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I'd have said the hardened seats started in '72. But Google disagrees:
=====================================
When did GM start using hardened valve seats?
1971
1971 was the first year for induction *hardened valve seats* from the
factory as far as I know. All engines by then had low compression ratios in
1971 compared to 1970 engines.Jan 29, 2011
=====================================
I trust that. And know from experience that trying to use Chevrolet
inserts won't work -- they're too thick and intrude into the Olds water
jacket.
Ken H.
On Mon, Dec 21, 2020 at 3:45 PM Robert J. Gogan via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I purchased a used J head from a 1975 Oldsmobile Cutlass 455. The
> rebuilder that I am using cannot tell if the exhaust seats were induction
> hardened
> during the original build. He can install hardened seats if I insist but
> he is concerned that can open up a can of worms. Any engine overheating or
> exhaust restriction will cause the seat to become undone in the head.
> This already happened to me in my air cooled Briggs and Stratton riding lawn
> tractor. Mice had built a nest under the air cooling baffles and the
> engine over heated and the hardened seats popped out. Tried some internet
> magic
> epoxy to rebed the seats but the fix lasted for only one trip around the
> lawn.
> Does anyone know if GM was supplying J-heads with hardened exhaust valve
> seats in 1975 so I don't have to deal with this problem?
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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| Re: [GMCnet] hardened exhaust valve seats [message #361066 is a reply to message #361064] |
Mon, 21 December 2020 15:48 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Senior Member |
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I have personally installed too many valve seats to remember. At one time
in my life, I was in a partnership with a guy in an automotive engine
machine shop. I spent many hours pulling seats, grinding away material that
was damaged by anti-freeze corrosion, then welding, then re-machining seat
pockets and pressing in new hardened seats. Finally, cutting new guides and
finally a three angle valve seat. Literally hundreds of them. Only had a
few failures, most of them attributed to being in too much of a hurry to
exercise sufficient caution to do it right. My fault, no one else's. So
what does this have to do with Oldsmobile "smogger" heads? Well, quite a
bit, actually. The alloy content of the heads is important, because of the
expansion rate. It is vital to know how much expansion takes place, and at
what temperature it occurs. Valve seats are "interference fit". That is
when the outside diameter is actually larger than the bore it is pressed
into. This is accomplished by heating the head until it expands larger than
the seats. In some cases, the seats must be super cooled, usually with a
CO2 fire extinguisher. -90° Farenheit is damn cold. Bare handed, it will
destroy your skin. So, heat the head, cool the seats, and press them home.
Then after temps have equalized, a ridge is rolled around the seats. They
will not fall out. Ever. Water cooled engines will not approach the
critical temperatures needed to expand enough for the seats to come loose.
Obviously, precision tooling, very sharp, and precision machinery are all
involved. Hand held tools won't work.
Jim Hupy
Salem, Oregon
On Mon, Dec 21, 2020, 1:15 PM Ken Henderson via Gmclist <
gmclist@list.gmcnet.org> wrote:
> I'd have said the hardened seats started in '72. But Google disagrees:
> =====================================
> When did GM start using hardened valve seats?
> 1971
> 1971 was the first year for induction *hardened valve seats* from the
> factory as far as I know. All engines by then had low compression ratios in
> 1971 compared to 1970 engines.Jan 29, 2011
> =====================================
> I trust that. And know from experience that trying to use Chevrolet
> inserts won't work -- they're too thick and intrude into the Olds water
> jacket.
> Ken H.
>
>
> On Mon, Dec 21, 2020 at 3:45 PM Robert J. Gogan via Gmclist gmclist@list.gmcnet.org> wrote:
>
>> I purchased a used J head from a 1975 Oldsmobile Cutlass 455. The
>> rebuilder that I am using cannot tell if the exhaust seats were induction
>> hardened
>> during the original build. He can install hardened seats if I insist but
>> he is concerned that can open up a can of worms. Any engine overheating
> or
>> exhaust restriction will cause the seat to become undone in the head.
>> This already happened to me in my air cooled Briggs and Stratton riding
> lawn
>> tractor. Mice had built a nest under the air cooling baffles and the
>> engine over heated and the hardened seats popped out. Tried some
> internet
>> magic
>> epoxy to rebed the seats but the fix lasted for only one trip around the
>> lawn.
>> Does anyone know if GM was supplying J-heads with hardened exhaust valve
>> seats in 1975 so I don't have to deal with this problem?
>>
>> _______________________________________________
>> GMCnet mailing list
>> Unsubscribe or Change List Options:
>> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
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| Re: hardened exhaust valve seats [message #361077 is a reply to message #361063] |
Tue, 22 December 2020 08:42 |
6cuda6
Messages: 975
Registered: June 2019
Karma: -6
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Senior Member |
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If your unsure or really worried about it....just use stainless exhaust valves. The guy that does all the GM aluminum block r&d work lived near me and thatis what he recommended on my 500hp stroked 340 instead of putting mucho money in aftermarket hardened seats.
Rich Mondor,
Brockville, ON
77 Hughes 2600
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| Re: [GMCnet] hardened exhaust valve seats [message #361080 is a reply to message #361077] |
Tue, 22 December 2020 11:13 |
jimk
Messages: 6734
Registered: July 2006
Location: Belmont, CA
Karma: 9
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Senior Member |
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Should you ever need to insert the Hard treated valve seats, let the
machine shop know , not to use the Chevrolet ones as they will need to cut
in so deep that the head will be worthless.
We get people needing heads where the machine shop ruined them.
On Tue, Dec 22, 2020 at 6:43 AM 6cuda6--- via Gmclist <
gmclist@list.gmcnet.org> wrote:
> If your unsure or really worried about it....just use stainless exhaust
> valves. The guy that does all the GM aluminum block r&d work lived near me
> and
> thatis what he recommended on my 500hp stroked 340 instead of putting
> mucho money in aftermarket hardened seats.
> --
> Rich Mondor,
>
> Brockville, ON
>
> 77 Hughes 2600
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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>
--
Jim Kanomata
Applied/GMC, Newark,CA
jimk@appliedairfilters.com
http://www.gmcrvparts.com
1-800-752-7502
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Jim Kanomata
Applied/GMC
jimk@appliedairfilters.com
www.appliedgmc.com
1-800-752-7502
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| Re: [GMCnet] hardened exhaust valve seats [message #361081 is a reply to message #361080] |
Tue, 22 December 2020 12:33 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Telling the machine shop to use olds seats rather then Chevy seats may come on deaf ears. I told my guy do not try to use Chevy seats or you will go into the water jacket sure enough he ruined the head luckily he had another head of course he blamed it on the head not his dumb idea.
Roy Keen
Minden,NV
76 X Glenbrook
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