fig1 shows a sand core 100 for a high - pressure oil rail according to the prior art . the sand core 100 has metal tube 110 supporting an outer portion 120 having the shape of the high - pressure oil rail . the outer portion 120 is made from a mixture of foundry sand and a binder . the metal tube 110 has a first end 150 and a second end 160 . in making a typical sand core 100 , the metal tube 110 is positioned inside the cavity of a core box ( not shown ). the cavity has the shape of the high - pressure oil rail . the core box typically has two parts that fit together along a parting line 140 to form the cavity . the sand and binder mixture is then poured into the cavity , surrounding and filling the previously positioned metal tube 110 . once the sand is set , the sand core 100 is removed from the core box for further processing and subsequent drying or curing . the nature of the sand - binder mixture results in inter - granular spacing ( not visible ) between the sand grains . the inter - granular - spacing is primarily occupied by the binder material . however , voids 145 and 148 form on the outer surface of the outer portion 120 when the inter - granular spacing becomes large enough and the binder material does not adequately fill the space causing . the two part core box also causes voids 145 to form on the outer surface of the outer portion 120 along the parting line 140 . it will be readily appreciated that there are to be more voids 145 and 148 on the unseen rear surface of the outer portion 120 in fig1 . if the core box has more parts , voids 145 would form on the additional parting lines 140 . in addition , the voids 145 may be located differently if the core box parts fit together differently . during casting , the voids 145 and 148 cause molten iron to penetrate into the sand core 100 . iron penetration results in parting line fins , veins , and other imperfections on the surface of the high - pressure oil rail . these imperfections in the casting surface must be removed by machining or grinding . when the sand core 100 is made , the support member or tube is usually filled with the sand and binder material . alternatively , plugs ( not shown ) may be inserted into the first end 150 and second end 160 of the metal tube 110 . the plugs are usually made from sand , but another refractory or suitable material may be used . both the sand and binder mixture and the plugs prevent molten iron from entering the metal tube 110 during casting . fig2 shows a preferred embodiment of the ceramic fiber casting core 200 according to the present invention . in this embodiment of the present invention a ceramic fiber casting core is used to make a high - pressure rail cavity or passage in a casted engine block that will accept a hydraulic actuating fluid . the pressures encountered in the high - pressure rail cavity in an engine block are typically in the range of 500 - 3 , 500 pounds per square inch ( psi ). and , the hydraulic actuating fluid encountered in the high - pressure fluid is preferably used to actuate engine components , e . g ., to actuate fuel injectors . also , in a preferred embodiment , the hydraulic actuating fluid is engine lubricating oil but may be other appropriate fluids . those of skill in the art will readily appreciate that the ceramic fiber casting core 200 can be configured to any desired shape to fit a particular casting application , not specific to engines . further , in this embodiment , the ceramic fiber casting core 200 has a ceramic fiber physical structure or portion 220 and a support member or tube 210 supporting relation to the ceramic structure 220 . the support member 210 provides structural support for the ceramic fiber casting core 200 during the casting of a metal part . as mentioned already , certain embodiments of the present invention may have a ceramic fiber structure 220 and no support member 210 . the specific parameters and applications requiring a ceramic fiber casting core 200 will determine whether or not a support member 210 is needed . the casting core 200 shown in fig2 has the shape of the high - pressure oil rail , which has a large length which in turn necessitates a support member 210 . the ceramic fiber structure or sleeve 220 is made from a mixture of ceramic fiber and a binder . the support member or tube 210 provides structural support for the ceramic fiber sleeve 220 . further , the support member is preferably a metal tube with a first end 250 and a second end 260 . the support member or tube 210 may also be a solid or hollow cylindrical bar , and may be made from plastic , ceramic , steel or any other material able to withstand the temperatures and stresses of iron casting . in addition , in another embodiment of the present invention , there may be an intermediate sleeve ( not shown ) between the support member 210 and the outer ceramic fiber portion 220 . the intermediate sleeve would enable or improve the connection of the support tube 210 to the ceramic fiber portion or sleeve 220 . the intermediate sleeve would also assist in removing the ceramic fiber casting core 200 after casting . the intermediate sleeve may also be any material suitable for these purposes including paper or cardboard , ceramics , and composites . fig3 is a flowchart showing a preferred method for manufacturing the ceramic fiber casting core 200 according to the present invention . in step 310 , ceramic fiber and binder are mixed in a mixing medium , e . g ., a mixing tank , to form a ceramic fiber slurry . the ceramic fiber may be any ceramic fiber suitable for casting processes and for core making . in a preferred embodiment , the ceramic fiber is preferably an alumino - silicate ( al 2 o 3 . sio 2 ) fiber . further , the binder should be suitable for use with the ceramic fiber and is typically organic . in step 320 , the ceramic fiber slurry is placed or poured into a vacuum forming tank . a perforated mandrel is then placed into the ceramic fiber slurry . a vacuum is created inside the perforated mandrel , causing the ceramic fiber slurry to deposit on the outside surface of the mandrel and form a ceramic fiber structure , portion or sleeve around the perforated mandrel . the time in the vacuum forming tank will determine the amount of ceramic fiber material deposited on the perforated mandrel through vacuum depositing . when sufficient ceramic fiber material is vacuum deposited , the perforated mandrel is removed from the vacuum forming tank . in step 330 , the ceramic fiber structure or sleeve 220 is removed from the perforated mandrel . in a preferred embodiment , the ceramic fiber structure , portion or sleeve can slide off the mandrel . the ceramic fiber portion or sleeve 220 is then conveyed to an oven for drying or curing . the perforated mandrel can then be returned to the vacuum forming tank to form another ceramic fiber sleeve 220 , as described in step 320 . in step 340 , the ceramic fiber sleeve 220 is dried or cured in a convection or radio frequency ( rf ) oven . other ovens may be used if they are suitable for the drying or curing process . if a convection oven is used , the ceramic fiber sleeve 220 is hung on a rack for transporting it through the oven . the rack permits air to flow around the ceramic fiber sleeve 220 . if an rf oven is used , the ceramic fiber sleeve 220 is transported through the oven by either a conveyor belt or a rack . in step 350 , the ceramic fiber structure or sleeve 220 is removed from the oven . in this embodiment , a support member or tube 210 is then located in supporting relation to the ceramic fiber structure or sleeve 220 to form an unfinished ceramic fiber casting core ( not shown ). the support member 210 provides structural support for the ceramic fiber structure 220 during the casting of a metal part . the ceramic fiber casting core is unfinished because the exterior of the ceramic fiber sleeve 220 is “ fluffy ” as a result of the drying or curing process . this “ fluffy ” exterior must be machined or ground to a desired size . as mentioned previously , some casting applications may only require an embodiment of the ceramic fiber casting core 200 with a ceramic fiber structure 220 and no support member 210 . those of skill in the art will readily recognize that a determination of whether or not a support member 210 is required will depend on the specific parameters and dimensions of the metal part being cast . in step 360 , the unfinished ceramic fiber casting core is machined or ground to remove the “ fluffy ” exterior and give the casting core the desired predetermined physical structure or configuration and proper dimensions for the engine part . for a high - pressure oil rail , machining the ceramic fiber casting core will produce a long cylindrical shaped casting core with a smooth surface . for other engine parts , machining permits the exterior of the ceramic fiber casting core to be configured to various dimensions , and structures or shapes . the machining and grinding gives the ceramic fiber casting core a smooth surfaces and precise dimensions . a casting core with smooth surfaces and more precise dimensions provides an as - cast part with smooth surfaces and precise dimensions , virtually eliminating the need to further machine or grind this area of the casting . in step 370 , the ceramic fiber casting core 200 is tested and inspected . the testing and inspection includes measuring the surface hardness , checking its dimensions , determining its loss on ignition , and assessing other factors that may affect its performance . if the ceramic fiber casting core 200 “ passes ” the inspection and tests , it is ready for use . a ceramic fiber casting core 200 made in this manner will not have the parting line 140 and voids 145 and 148 associated with existing sand cores 100 ( shown in fig1 ). consequently , the ceramic fiber casting core 200 does not need core wash or another refractory coating . although not shown , the ceramic fiber casting core 200 may undergo post treatment after testing and inspection . the post treatment may be to correct some “ failure ” identified during testing and inspection . the inspection may reveal the diameter of the ceramic fiber casting core 200 is not to the desired tolerance . in addition , the post treatment may also improve the ceramic fiber casting core 200 . for example , the ceramic fiber casting core 200 may be impregnated with another material to enhance and improve its casting capabilities . prior to placing the ceramic fiber casting core in a mold part , plugs ( not shown ) may be inserted into the first and second ends 250 and 260 of the support tube 210 . the plugs are made of cork or other suitable material . the plugs prevent molten iron from entering the support tube 210 during casting . using plugs can eliminate sand from the coremaking process . fig4 - 11 show cross - sectional side and full end views of alternate embodiments or applications using the ceramic fiber casting core 200 of the present invention to produce a high - pressure oil rail in an engine . the ceramic fiber casting cores are shown in their as - cast position inside the casting . the ceramic fiber casting cores and oil rails are symmetrical in these views . however , those of skill in the art will recognize that the ceramic fiber casting core 200 may take different structures or configurations , even asymmetrical , to produce other engine parts . for comparison purposes , the oil rails depicted in fig4 - 11 all have essentially the same length . fig4 - 11 further show various embodiments of the ceramic fiber casting core 200 with varying physical end structures and inside oil rail diameter . these features provide advantages for the present invention . in high - pressure oil rails , sealing plugs are typically mounted in the ends of the oil passage . presently , the ends of the oil rail are machined to receive the sealing plugs . while the inside diameter of the oil rail remains sufficient to maintain the volume and pressure of the oil for the injectors . fig4 shows a side - section view of a ceramic fiber casting core 400 in its as - cast position inside the oil rail casting 405 . this embodiment has the same physical structure as a typical sand core . the ceramic fiber casting core 400 is comprised of a support tube 410 inside a ceramic fiber sleeve 420 . the ceramic fiber casting core 400 forms an oil rail passage 425 having diameter a ( shown in fig5 ). the ceramic fiber casting core 400 and oil rail casting 405 have a first end 450 and a second end 460 . fig5 shows a first end 450 that corresponds to a full end view of the ceramic fiber casting core 400 of fig4 . fig6 shows a side - section view of a ceramic fiber casting core 600 in its as - cast position inside the oil rail casting 605 . this embodiment is also the same as a typical sand core . the ceramic fiber casting core 600 again is comprised of a support tube 610 inside a ceramic fiber sleeve 620 . however , the ceramic fiber casting core 600 forms an oil rail passage 625 having diameter b ( shown in fig7 ). the ceramic fiber casting core 600 and oil rail casting 605 have a first end 650 and a second end 660 . fig7 shows the first end 650 that corresponds to a full end view of the ceramic fiber casting core 600 of fig6 . comparing the embodiments of fig4 and 6 , oil rail passage 625 ( diameter b ) is larger than oil rail passage 425 ( diameter a ). oil rail casting 405 has sufficient thickness for machining the sealing surfaces ( not shown ) at ends 450 , 460 . however , oil rail casting 405 also has excess material , the unmachined portion in its center , which increases the engine &# 39 ; s weight and size . in contrast , oil rail casting 605 is sized according to the oil rail passage which minimizes its size and weight . a possible downside of this embodiment is that oil rail casting 605 permits no internal machining since there is insufficient material for machining the sealing surfaces . thus , the ceramic fiber casting cores embodiments of fig4 and 6 possess different features and advantages . fig8 shows a side - section view of a ceramic fiber casting core 800 in its as - cast position inside the oil rail casting 805 . the ceramic fiber casting core 800 in this embodiment has an advantageous physical structure that would be difficult , if not impossible , to duplicate in a typical sand core within dimensional tolerances suitable for casting operations . the ceramic fiber casting core 800 is comprised of a support tube 810 inside a ceramic fiber sleeve 820 . the ceramic fiber casting core 800 forms an oil rail passage 825 having diameter c ( shown in fig9 ). the ceramic fiber casting core 800 and oil rail casting 805 have a first end 850 and a second end 860 . moreover , in this embodiment , the ceramic fiber casting core 800 forms a taper 830 at each end 850 and 860 . the taper 830 forms a taper opening 840 at each end 850 and 860 . the diameter of the taper opening 840 is smaller than the diameter c of the oil rail passage 825 . fig9 shows the first end 850 , which corresponds to a full end view of the ceramic fiber casting core 800 of fig8 . fig1 shows a side section view of a ceramic fiber casting core 900 in its as - cast position inside the oil rail casting 905 . again , the ceramic fiber casting core 900 in this embodiment also has an advantageous physical structure that would be difficult to duplicate in a typical sand core within dimensional tolerances suitable for casting operations . the ceramic fiber casting core 900 is comprised of a support tube 910 inside a ceramic fiber sleeve 920 . the ceramic fiber casting core 900 forms an oil rail passage 925 having diameter d ( shown in fig1 ). in this embodiment , diameter d may be the same as diameter c . the ceramic fiber casting core 900 and oil rail casting 905 have a first end 950 and a second end 960 . the ceramic fiber casting core 900 forms a taper 930 at each end 950 and 960 . the taper 930 forms a taper opening 940 at each end 950 and 960 . the diameter of the taper opening 940 is smaller than diameter d of the oil rail passage 925 . moreover , the taper opening 940 is smaller than the taper opening 840 of the embodiment shown in fig8 . fig1 shows the first end 950 , which corresponds to a full end view of the ceramic fiber casting core 900 of fig1 . taper openings 830 and 930 provide additional finish stock for the machining of the sealing surfaces at the ends 850 , 860 , 950 and 960 of the oil rail castings 805 and 905 . the taper openings 830 and 930 reduce the size and weight of the oil rail castings 805 and 905 . in addition , taper opening 930 provides more finish stock on oil rail casting 905 than taper opening 830 provides for oil rail casting 805 . as a result , opening 940 is smaller than opening 840 . a smaller threaded plug may thus be used to seal oil rail casting 905 compared to the seal plug for oil rail casting 805 . this feature results in greater cost reduction to manufacturing an engine part - using the embodiment of fig1 . the invention has been described in relation to a ceramic fiber casting core , and method for such core , for use in making a high - pressure rail cavity or passage in an internal combustion engine that accepts hydraulic actuating fluid . however , those of skill in the art will readily recognize that the invention may be used to provide ceramic fiber casting cores in casting other metal parts , including , but not limited to , engine parts . the present invention is particularly suited for applications using casting cores of variable dimensions and shapes which may or may not required the use of a support member . this is the case since the ceramic fiber casting core of the present invention is capable of being configured , machined and ground to any desired surface shape and dimensions . thus , the present invention has been described and illustrated by way of certain preferred embodiments only . the invention may also be used to manufacture or cast engine parts , other than the high - pressure oil rail specifically discussed herein . additional advantages will be readily apparent to those skilled in the art , who may modify the embodiments without departing from the true spirit and scope of the invention . therefore , this invention is not limited to the specific details , representative devices , and illustrated examples in this description . the present invention is limited only by the following claims and equivalents .