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Re: Valve seat fit

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  • marshengnz
    OK .007 - .008 is 0.17-0.20. This is for cars so I might be a bit smaller than this. 1/250 is 0.145 - Close to what I have. I think that I have been getting
    Message 1 of 28 , Feb 1, 2011
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      OK .007 - .008 is 0.17-0.20. This is for cars so I might be a bit smaller than this.

      1/250 is 0.145 - Close to what I have.

      I think that I have been getting interference fits all wrong.

      The chap that sold the guide said it is about 0.05 interference fit.
      That really means 0.10 oversize as it is 0.05 on each side.

      I think we get mixed up with piston clearance which is measured in total. Ie 2 thou clearance is actually 1 thou either side but we say 2 thou clearance. Does interference not mean one face to another.

      The question, a cast iron cylinder sleeve in a aly barrel, is it 0.08 mm interference fit which means bore + 0.16mm ?


      Thanks Wallace
    • Ian
      ... So you would put an old BMW intake seat in with nearly 0.30mm interference ?? That s VERY VERY tight Hans. Cheers IAN See www.drysdalev8.com for :
      Message 2 of 28 , Feb 1, 2011
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        >I use the "rule of thumb" 1/250 x diameter, that works good for me
        >with most head materials. Only for the old soft BMW-heads up to
        >1/175 x dia. is recommended.


        So you would put an old BMW intake seat in with nearly 0.30mm interference ??

        That's VERY VERY tight Hans.



        Cheers IAN


        See www.drysdalev8.com for :
        - Drysdale 750-V8 Sports & 1000-V8 Cruiser
        - DRYVTECH 2x2x2 Experimental
        - Carberry Enfield 1000cc V-Twin
        - Drysdale Hillclimb Open Wheeler
      • Ian
        ... Interference is always taken as TOTAL, not PER SIDE. Cheers IAN See www.drysdalev8.com for : - Drysdale 750-V8 Sports & 1000-V8 Cruiser - DRYVTECH
        Message 3 of 28 , Feb 1, 2011
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          >The chap that sold the guide said it is about 0.05 interference fit.
          >That really means 0.10 oversize as it is 0.05 on each side.


          Interference is always taken as TOTAL, not PER SIDE.


          Cheers IAN


          See www.drysdalev8.com for :
          - Drysdale 750-V8 Sports & 1000-V8 Cruiser
          - DRYVTECH 2x2x2 Experimental
          - Carberry Enfield 1000cc V-Twin
          - Drysdale Hillclimb Open Wheeler
        • hans_o_man
          Good thanks I own no BMW :-) but you are right. I would be afraid of shrinking in a seat with that interference. This recommendation comes from an old BMW
          Message 4 of 28 , Feb 1, 2011
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            Good thanks I own no BMW :-) but you are right. I would be afraid of shrinking in a seat with that interference. This recommendation comes from an old BMW engine-mechanik, and in the moment I'm not shure, if he was kidding.


            --- In mc-engine@yahoogroups.com, Ian <iwd@...> wrote:
            >
            >
            > >I use the "rule of thumb" 1/250 x diameter, that works good for me
            > >with most head materials. Only for the old soft BMW-heads up to
            > >1/175 x dia. is recommended.
            >
            >
            > So you would put an old BMW intake seat in with nearly 0.30mm interference ??
            >
            > That's VERY VERY tight Hans.
            >
            >
            >
            > Cheers IAN
            >
            >
            > See www.drysdalev8.com for :
            > - Drysdale 750-V8 Sports & 1000-V8 Cruiser
            > - DRYVTECH 2x2x2 Experimental
            > - Carberry Enfield 1000cc V-Twin
            > - Drysdale Hillclimb Open Wheeler
            >
          • mike lowe
            I ve made lots of seats for cars, mostly out of old hydraulic ram spears, abate not performance stuff other wise I buy proper seats. Lead and surface finish is
            Message 5 of 28 , Feb 1, 2011
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              I've made lots of seats for cars, mostly out of old hydraulic ram
              spears, abate not performance stuff other wise I buy proper seats.
              Lead and surface finish is as important as fit. I use .003" as basic
              rule of thumb but, that depends on the section of the seat and how
              hard the head material is. With really fat seats ie where I've had to
              bore the hole out to some ridiculous size to get rid of damage, I've
              gone down to .0015.
              I make a dolly and tap them in cold. If the fits right they sound
              and feel right when you tap them in. When it get to the bottom of the
              hole the hammer should have a sudden and nice bounce to it. Or,
              somethings wrong.
              It is nigh on impossible to press them in, as some think they
              should be.

              Interestingly, I made a seat for a Mac truck head (valve the size of a
              tennis ball) some time back using the .003" rule and it promptly
              dropped out as soon as it reached running temp. Turned out the genuine
              Mac seats only have .004" interference, I literally pushed it in with
              my thumbs. But it didn't fall out.
              The more expensive the engine is the more nervous I get but so far
              that the only failure I've had. Touch wood :0)

              Mike Lowe
            • Ken Augustine
              Old /2 BMWs would be running fine when shut down at night then go clank when kicked over in the morning as cool air could waft up the exhaust pipe to an open
              Message 6 of 28 , Feb 1, 2011
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                Old /2 BMWs would be running fine when shut down at night then go clank when kicked over in the morning as cool air could waft up the exhaust pipe to an open exhaust valve, the seat would contract from the warm head and fall down the valve stem.   The head would then cool and the seat would be trapped down the stem, messing up  everything when the piston was kick started into it.   An extra .002"f press would have eliminated the problem but I don't know what the original press fit had been or the hardness of the aluminum.  

                If the insufficient interference was called material softness, I wouldn't be surprised but proper interference always fixed the situation.  

                Ken A

                From: hans_o_man <der_hiha@...>
                To: mc-engine@yahoogroups.com
                Sent: Tue, February 1, 2011 1:17:09 AM
                Subject: Re: Valve seat fit

                 

                Good thanks I own no BMW :-) but you are right. I would be afraid of shrinking in a seat with that interference. This recommendation comes from an old BMW engine-mechanik, and in the moment I'm not shure, if he was kidding.

                --- In mc-engine@yahoogroups.com, Ian <iwd@...> wrote:
                >
                >
                > >I use the "rule of thumb" 1/250 x diameter, that works good for me
                > >with most head materials. Only for the old soft BMW-heads up to
                > >1/175 x dia. is recommended.
                >
                >
                > So you would put an old BMW intake seat in with nearly 0.30mm interference ??
                >
                > That's VERY VERY tight Hans.
                >
                >
                >
                > Cheers IAN
                >
                >
                > See www.drysdalev8.com for :
                > - Drysdale 750-V8 Sports & 1000-V8 Cruiser
                > - DRYVTECH 2x2x2 Experimental
                > - Carberry Enfield 1000cc V-Twin
                > - Drysdale Hillclimb Open Wheeler
                >

              • Ken Augustine
                Air cooled VW valve seats are often staked in after installation and Wright aircraft heads wound up having their valve seats being screwed in then staked with
                Message 7 of 28 , Feb 1, 2011
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                  Air cooled VW valve seats are often staked in after installation and Wright aircraft heads wound up having their valve seats being screwed in then staked with the later valve seats trapped by a screwed in ring and actually allowed to float radially to conform to the valve stem axis as that changed with temperature. 

                  All this was fixed by substituting a jet turbine engine for the reciprocating unit.  

                  Ken A



                  From: mike lowe <mikelowe@...>
                  To: mc-engine@yahoogroups.com
                  Sent: Tue, February 1, 2011 1:36:10 AM
                  Subject: Re: Valve seat fit

                   

                  I've made lots of seats for cars, mostly out of old hydraulic ram
                  spears, abate not performance stuff other wise I buy proper seats.
                  Lead and surface finish is as important as fit. I use .003" as basic
                  rule of thumb but, that depends on the section of the seat and how
                  hard the head material is. With really fat seats ie where I've had to
                  bore the hole out to some ridiculous size to get rid of damage, I've
                  gone down to .0015.
                  I make a dolly and tap them in cold. If the fits right they sound
                  and feel right when you tap them in. When it get to the bottom of the
                  hole the hammer should have a sudden and nice bounce to it. Or,
                  somethings wrong.
                  It is nigh on impossible to press them in, as some think they
                  should be.

                  Interestingly, I made a seat for a Mac truck head (valve the size of a
                  tennis ball) some time back using the .003" rule and it promptly
                  dropped out as soon as it reached running temp. Turned out the genuine
                  Mac seats only have .004" interference, I literally pushed it in with
                  my thumbs. But it didn't fall out.
                  The more expensive the engine is the more nervous I get but so far
                  that the only failure I've had. Touch wood :0)

                  Mike Lowe

                • hans_o_man
                  I have a pic of WW2-aircraft valve seat, shrink-screwed: http://www.nefo.med.uni-muenchen.de/~hiha/bilder/Museum01/DB605-ventilsitz.jpg With soft head I
                  Message 8 of 28 , Feb 1, 2011
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                    I have a pic of WW2-aircraft valve seat, shrink-screwed:
                    http://www.nefo.med.uni-muenchen.de/~hiha/bilder/Museum01/DB605-ventilsitz.jpg

                    With "soft head" I meant an alloy with high thermal expansion, which is also quite soft when warm.
                    Cheers,
                    Hans
                  • Ken Augustine
                    All aluminum heads are soft when heated enough. Part of the trick to longevity of aluminum heads is to not allow them get too hot. Water cooling helps
                    Message 9 of 28 , Feb 1, 2011
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                      All aluminum heads are soft when heated enough.   Part of the trick to longevity of aluminum heads is to not allow them get too hot.   Water cooling helps immensely and free exhaust breathing is crucial.  

                      If you want to make a IC engine run hot, block up the exhaust.  -  Ken A



                      From: hans_o_man <der_hiha@...>
                      To: mc-engine@yahoogroups.com
                      Sent: Tue, February 1, 2011 2:09:15 AM
                      Subject: Re: Valve seat fit

                       

                      I have a pic of WW2-aircraft valve seat, shrink-screwed:
                      http://www.nefo.med.uni-muenchen.de/~hiha/bilder/Museum01/DB605-ventilsitz.jpg

                      With "soft head" I meant an alloy with high thermal expansion, which is also quite soft when warm.
                      Cheers,
                      Hans

                    • Ian
                      ... Aircraft engines still run on the ragged edge cylinder head temp wise, helicopters will routinely drop valve seats if not run down for 3 minutes. Not
                      Message 10 of 28 , Feb 1, 2011
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                        >Air cooled VW valve seats are often staked in after installation and
                        >Wright aircraft heads wound up having their valve seats being
                        >screwed in then staked with the later valve seats trapped by a
                        >screwed in ring and actually allowed to float radially to conform to
                        >the valve stem axis as that changed with temperature.


                        Aircraft engines still run on the ragged edge cylinder head temp wise,
                        helicopters will routinely drop valve seats if not "run down" for 3 minutes.
                        Not such an issue with fixed wind as they're effectively idling when on
                        approach and then taxi at low power back to the hangar, a chopper is
                        at close to full power in hover, so it lands with a hot engine.


                        >All this was fixed by substituting a jet turbine engine for the
                        >reciprocating unit.


                        Amen.


                        Cheers IAN


                        See www.drysdalev8.com for :
                        - Drysdale 750-V8 Sports & 1000-V8 Cruiser
                        - DRYVTECH 2x2x2 Experimental
                        - Carberry Enfield 1000cc V-Twin
                        - Drysdale Hillclimb Open Wheeler
                      • 750guy
                        Hi All, This may be an off the wall question but can a valve seat be pushed in (loose fit) with a JB Weld type of epoxy. Then staked? I have the problem in an
                        Message 11 of 28 , Feb 1, 2011
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                          Hi All,
                           This may be an off the wall question but can a valve seat be pushed in (loose fit) with a JB Weld type of epoxy. Then staked?  I have the problem in an old 2 cylinder air cooled OMC Cushman motor that has a loose valve seat, air cooled aluminum head and cylinder in one piece, very low power/RPM. 18 HP. It was in a 3 wheeled truckster but it's going in a bike.
                          Joe
                           
                        • Jamie Worthington
                          I was given a john deere garden tractor that had a kawasaki 12 horse engine that had the exhaust seat come out, probably due to overheating. I just put it back
                          Message 12 of 28 , Feb 1, 2011
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                            I was given a john deere garden tractor that had a kawasaki 12 horse engine that had the exhaust seat come out, probably due to overheating. I just put it back in and staked it.

                            Only after I did that, did I see a service manual which said to stake the seat in after replacement. I am assuming this happened quite a bit (the seats falling out) , for this information about staking to be included in the manual.

                            I have not any issues since. If enough material exist to stake the seat, and it wasn't loose at room temp, I don't know that you would need anything else. But I do believe loctite makes a product specifically for this. (620?)

                            750guy <the750guy@...> wrote:

                            >Hi All,
                            > This may be an off the wall question but can a valve seat be pushed in (loose fit) with a JB Weld type of epoxy. Then staked? I have the problem in an old 2 cylinder air cooled OMC Cushman motor that has a loose valve seat, air cooled aluminum head and cylinder in one piece, very low power/RPM. 18 HP. It was in a 3 wheeled truckster but it's going in a bike.
                            >Joe
                          • GStarRon@aol.com
                            Any engine that I have seen that has had a valve seat come out when running made a big mess... Why not do it properly..?? On an aluminum (large type 2
                            Message 13 of 28 , Feb 1, 2011
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                              Any engine that I have seen that has had a valve seat come out when running made a big mess...  Why not do it properly..??   On an aluminum (large type 2 valve) head, anything under 0.003" is marginal, 0.005" is better but more difficult to install... at 0.007 it should never go anywhere..!  Using the liquid Nitrogen will shrink a steel valve seat a bunch (done properly.. then head the head... but also make sure some pressure is kept on the seat until the temperatures are evened out.... as the seat could move during that time..  (Same with the installation of a cylinder liner, keep pressure on it until the cylinder cools off..or it may move).    Yes with an iron head the fit can be a lot less than above.
                               
                              Now even IF a "loose" seat does not fall out due to staking it still can move, two things can happen, first it WILL allow leakage, and with leakage goes some of your H.P. next is the seat and or the head can get damaged, especially if the O.D. of the seat is close to the O.D. of the valve, as you may find in a high performance application.
                               
                              Valve seats are not expensive and come in many sizes and several manufacturers will make them to your spec, and one MFG will give you 24 hour turn around time...  They do not have a wide variety in choice of materials, but if you need a hardened steel seat fast, they can do it..!  http://www.tuckervalveseat.com/tucker_valve_services  I think they have a $50.00 minimum, but that would be about 2 seats and shipping...
                               
                              Ron
                            • Ian
                              ... If we re talking bush engineering........what about high temp silicon, then staked ? It s more of a get home fix than permanent fix, but silicon has a
                              Message 14 of 28 , Feb 1, 2011
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                                >This may be an off the wall question but can a valve seat be pushed
                                >in (loose fit) with a JB Weld type of epoxy. Then staked?


                                If we're talking bush engineering........what about high temp silicon, then
                                staked ? It's more of a "get home fix" than permanent fix, but silicon has
                                a much higher temp rating than epoxy.
                                _________________________________________________________

                                On this subject, there was a time when Ducati's were so unreliable that
                                dealers offered zero warranty, to the point where dealers didn't even start
                                them during pre-delivery. There was a dealer in the town near where I
                                grew up and he had 2 bevel 750's that didn't make it to the end of the
                                street before dropping the exhaust valve set out of the rear cylinder.
                                At least one of these ( after multiple rebuilds ) ended up with a Honda
                                750-4 engine in it, neat job too.

                                BTW - in the early 70's, Australia was the biggest market outside Italy
                                for Ducati, and also Laverda I believe, whose early triples also suffered
                                from seats coming loose.


                                Cheers IAN


                                See www.drysdalev8.com for :
                                - Drysdale 750-V8 Sports & 1000-V8 Cruiser
                                - DRYVTECH 2x2x2 Experimental
                                - Carberry Enfield 1000cc V-Twin
                                - Drysdale Hillclimb Open Wheeler
                              • marshengnz
                                Thanks for all the feedback. I we back to supplier of the seats. After scratching his head for a while he phoned one of his expert customers. His spec was 5
                                Message 15 of 28 , Feb 1, 2011
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                                  Thanks for all the feedback.

                                  I we back to supplier of the seats. After scratching his head for a while he phoned one of his expert customers. His spec was 5 thou or 0.12 mm. As the aly is soft can there be any problem with being too tight?

                                  The next problem I have is the old seat was 32.5 mm and the new 36.5. As this is a small motor, when I opened up the seat hole to 36.5, the total depth increased to more that the new valve seat width so it is useless.

                                  Buying things off the shelf always catches me out!!

                                  The best material I can find locally is Al Nickel Bronze AB2 and I have some on order. Copper Alloy No. C95800 Alpha Nickel Aluminum Bronze CDA 958 ASTM B 505 , ASTM B 271.

                                  I had to offset the valve seat hole away from the sparkplug by about a mm, but I can't see anything wrong with that.

                                  I'm going to try the Liquid nitrogen as I have not done that before and I keen to know how it works.

                                  Cheers Wallace.
                                • marshengnz
                                  I have a CBR150 head here that needed a new seat. The valve bent and dented the old seat. The seat measured 23.08 mm and the hole 23.02. I would say that the
                                  Message 16 of 28 , Feb 2, 2011
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                                    I have a CBR150 head here that needed a new seat. The valve bent and dented the old seat.

                                    The seat measured 23.08 mm and the hole 23.02. I would say that the original hole in the head was 23.oo mm. This gives an interference fit of 0.08. So with a 36 mm seat, 0.12 mm is not far off the mark.

                                    The seat was 7 mm long so it had a good face to mate on.

                                    Anyone in Carins on this list ?

                                    Cheers Wallace.
                                  • john fisher
                                    It doesn t look like Cairns ll be Inter-tubing for a while, does it? Thats a big storm. our sympathies.
                                    Message 17 of 28 , Feb 2, 2011
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                                      It doesn't look like Cairns'll be Inter-tubing for a while, does it? Thats a big storm.

                                      our sympathies.

                                      On 02/02/2011 12:58 PM, marshengnz wrote:

                                      > Anyone in Carins on this list ?
                                    • Ian
                                      ... I have a niece who lives there, she is OK, looks like it passed 60km to the south, so less damage than would otherwise have been done. You live in a
                                      Message 18 of 28 , Feb 2, 2011
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                                        >Anyone in Carins on this list ?


                                        I have a niece who lives there, she is OK, looks like it passed 60km to
                                        the south, so less damage than would otherwise have been done.

                                        You live in a tropical paradise, cyclones are one of the things that you
                                        have to put up with, along with crocodiles living in the swamp at the
                                        end of her street.



                                        Cheers IAN


                                        See www.drysdalev8.com for :
                                        - Drysdale 750-V8 Sports & 1000-V8 Cruiser
                                        - DRYVTECH 2x2x2 Experimental
                                        - Carberry Enfield 1000cc V-Twin
                                        - Drysdale Hillclimb Open Wheeler
                                      • marshengnz
                                        I did both seats today. My gas supplier arrived at the workshop and filled my thermos with liquid nitrogen. $6.50 a litre. I was quite surprised. Some energy
                                        Message 19 of 28 , Feb 3, 2011
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                                          I did both seats today. My gas supplier arrived at the workshop and filled my thermos with liquid nitrogen. $6.50 a litre. I was quite surprised. Some energy drinks cost more than that.

                                          The heat heated to 120degC and the seat at -200, didn't quite drop in but two lights taps with a small hammer and I heard that reassuring Ting Ting as the seat went fully home.

                                          We did the CBR150 seat as well without any problems.

                                          You do need a guide of sorts as there is no time to bugger around with it.

                                          The new seat should not center on the valve guide as they are not concentric. I allowed the seat to float in the holder. I set the seat and holder up in the head and gently nipped up the screw to hold it in position. I marked the head and seat and aligned them when assembling.

                                          Worked well and I would do it again.

                                          0.12 on the 36.5 mm seat and 0.08 on the 23 mm one.

                                          Thanks Chaps
                                        • Matt Patterson
                                          I have a question about dry ice. I m sure if I do a bit of local leg work then I can find it, but the DIY approach interests me. I did a google and found
                                          Message 20 of 28 , Feb 4, 2011
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                                            I have a question about dry ice.

                                            I'm sure if I do a bit of local leg work then I can find it, but the DIY
                                            approach interests me.

                                            I did a 'google' and found that either a CO2 fire extinghuisher or a CO2
                                            tank will work.....appartently.

                                            So I dashed home, dug out my best pillow case to make an 'ice bag' and
                                            succeeded in turning my workshop into a rock concert stage, but
                                            unfortunately no dry ice.

                                            I stole the CO2 off my Mig welder and then presumed that I'm not blowing the
                                            liquid out, just the gas, so disregarding any personal safety I laid the
                                            bottle with it's bottom slightly up and tried again. Possibly got a better
                                            effect for the rock stage, but still no dry ice.

                                            Should I give up and just go and buy it? Or go and buy a fire extinguisher
                                            and try again?

                                            Buying it is the easy option, but I get impulses late at night to make
                                            things and press things together, and my freezer is so full of bearings and
                                            shafts and what have you that there's no room for the Sunday roast, but I
                                            want to go colder than this, especialy after all this talk of liquid
                                            nitrogen.

                                            Any suggestions?

                                            Regards,

                                            Matt.
                                            www.tyga-performance.com



                                            ----- Original Message -----
                                            From: marshengnz
                                            To: mc-engine@yahoogroups.com
                                            Sent: Thursday, February 03, 2011 4:55 PM
                                            Subject: Re: Valve seat fit



                                            I did both seats today. My gas supplier arrived at the workshop and filled
                                            my thermos with liquid nitrogen. $6.50 a litre. I was quite surprised. Some
                                            energy drinks cost more than that.

                                            The heat heated to 120degC and the seat at -200, didn't quite drop in but
                                            two lights taps with a small hammer and I heard that reassuring Ting Ting as
                                            the seat went fully home.

                                            We did the CBR150 seat as well without any problems.

                                            You do need a guide of sorts as there is no time to bugger around with it.

                                            The new seat should not center on the valve guide as they are not
                                            concentric. I allowed the seat to float in the holder. I set the seat and
                                            holder up in the head and gently nipped up the screw to hold it in position.
                                            I marked the head and seat and aligned them when assembling.

                                            Worked well and I would do it again.

                                            0.12 on the 36.5 mm seat and 0.08 on the 23 mm one.

                                            Thanks Chaps
                                          • Danny Whitfield
                                            On Fri, Feb 4, 2011 at 9:09 AM, Matt Patterson ... Can t you buy liquid nitrogen? I saw a cooking show where they were dipping strawberrys into a liquid
                                            Message 21 of 28 , Feb 4, 2011
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                                              On Fri, Feb 4, 2011 at 9:09 AM, Matt Patterson
                                              <matt@...> wrote:
                                              >
                                              >
                                              >
                                              > I have a question about dry ice.
                                              >
                                              > I'm sure if I do a bit of local leg work then I can find it, but the DIY
                                              > approach interests me.
                                              >
                                              > I did a 'google' and found that either a CO2 fire extinghuisher or a CO2
                                              > tank will work.....appartently.
                                              >
                                              > So I dashed home, dug out my best pillow case to make an 'ice bag' and
                                              > succeeded in turning my workshop into a rock concert stage, but
                                              > unfortunately no dry ice.
                                              >
                                              > I stole the CO2 off my Mig welder and then presumed that I'm not blowing the
                                              > liquid out, just the gas, so disregarding any personal safety I laid the
                                              > bottle with it's bottom slightly up and tried again. Possibly got a better
                                              > effect for the rock stage, but still no dry ice.
                                              >
                                              > Should I give up and just go and buy it? Or go and buy a fire extinguisher
                                              > and try again?
                                              >
                                              > Buying it is the easy option, but I get impulses late at night to make
                                              > things and press things together, and my freezer is so full of bearings and
                                              > shafts and what have you that there's no room for the Sunday roast, but I
                                              > want to go colder than this, especialy after all this talk of liquid
                                              > nitrogen.
                                              >
                                              > Any suggestions?
                                              >
                                              > Regards,
                                              >
                                              > Matt.
                                              > www.tyga-performance.com
                                              >
                                              > ----- Original Message -----
                                              > From: marshengnz
                                              > To: mc-engine@yahoogroups.com
                                              > Sent: Thursday, February 03, 2011 4:55 PM
                                              > Subject: Re: Valve seat fit
                                              >
                                              > I did both seats today. My gas supplier arrived at the workshop and filled
                                              > my thermos with liquid nitrogen. $6.50 a litre. I was quite surprised. Some
                                              > energy drinks cost more than that.
                                              >
                                              > The heat heated to 120degC and the seat at -200, didn't quite drop in but
                                              > two lights taps with a small hammer and I heard that reassuring Ting Ting as
                                              > the seat went fully home.
                                              >
                                              > We did the CBR150 seat as well without any problems.
                                              >
                                              > You do need a guide of sorts as there is no time to bugger around with it.
                                              >
                                              > The new seat should not center on the valve guide as they are not
                                              > concentric. I allowed the seat to float in the holder. I set the seat and
                                              > holder up in the head and gently nipped up the screw to hold it in position.
                                              > I marked the head and seat and aligned them when assembling.
                                              >
                                              > Worked well and I would do it again.
                                              >
                                              > 0.12 on the 36.5 mm seat and 0.08 on the 23 mm one.
                                              >
                                              > Thanks Chaps


                                              Can't you buy liquid nitrogen? I saw a cooking show where they were
                                              dipping strawberrys into a liquid nitorgen thermos looking bottle to
                                              quick freeze them.

                                              Dan W
                                            • Ava Pxia
                                              http://www.speedzilla.com/forums/rc51-technical-discussion/64780-my-rc30-motor-bike-build-new-post.html Some interesting pictures of a head for a V4 RC30 and
                                              Message 22 of 28 , Mar 21 5:16 AM
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                                                http://www.speedzilla.com/forums/rc51-technical-discussion/64780-my-rc30-motor-bike-build-new-post.html

                                                Some interesting pictures of a head for a V4 RC30 and info on the alloys used with Ti valves.

                                                -------------- copy paste of alloy response ------------------------------
                                                Beryllium Copper alloy seat inserts matched with our titanium valves. Tight dimensional control of 0.0125mm ( 0.0005") is held. Tighter control is available where it is desired.
                                                Del West offers 2 Beryllium Copper alloys namely Alloy 25 and Alloy 3.
                                                • Alloy 25 has the optimal material properties best suited for the intake valve environment. This alloy is 98% copper and provides sufficient heat transfer and superior strength. This alloy will transfer the necessary heat to extend the intake valve life while being able to withstand the forces applied by the intake valve upon closing.
                                                • Alloy 3 has the optimal material properties best suited for the exhaust valve environment. This alloy is more than 97% copper and provides superior heat transfer and sufficient strength. This alloy will transfer the necessary heat from the exhaust valve into the cylinder head to help prevent premature seat pitting and heat related fractures.
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