CA1092919A - Insert for rebuilding valve guides and method for making same - Google Patents

Abstract

INSERT FOR REBUILDING VALVE GUIDES
AND METHOD FOR MAKING SAME

ABSTRACT OF THE DISCLOSURE
The specification discloses an insert for lining and/or relining valve guides for reciprocating-type poppet valves in cylinder heads of internal combustion engines, The insert has multiple layers of metallic materials and prefer-ably includes an inner sleeve or tube of spring-tempered phosphor bronze and an outer carrier sleeve or tube of steel or aluminum. The combined sleeves provide the insert with high wear resistance and lubricity and excellent heat transfer properties. Separate formation and later assembly allows precise control of wall thicknesses, diameters and concentricities.
Also disclosed is a method for manufacturing the insert including separately forming the inner and outer sleeves or tubes, and inserting one within the other for frictionally holding them together.

Description

2S~

1 BACKGROUND OF Tl-IE INVENTION
.______ Ihis invention relates to devices providing a lining for a valve guide to receive the stem of a recipro-cating type poppet valve in an internal combustion engine and, more particularly, to an insert particularly adapted to line or reline a worn valve guide to return it to its original or better operating condition.
Inserts -for lining or relining worn valve guides in internal combustion engines are well known. Typically, the worn valve guide of an internal combustion engine is bored out to receive a cast iron insert having an inside diameter which receives the stem of a valve Eitted there-through. The cast iron sleeve is force fitted into or otherwise retained in the bored-out valve guide passageway.
Cast iron inserts of this type suffer from two major disadvantages. They are relatively expensive to manufacture, the meeting of tolerances with respect to wall thickness and concentricity requiring generally repeat ma-chining of either the inner or outer insert surfaces fol-lowing initial machining of the insert. The wear charac-teristics of these cast iron inserts, most importantly, leave much to be desired. They do offer the advantages~ however, of having good heat transfer characteristics and have for years been produced in standard O.D. sizes minimizing the number of specialized tools required for installation.
Materials possessing wear characteristics sub-stantially better than cast iron have been known for a substantial period of time. In this inventor's prior U.S.
patents 3,828,415 and 3,828~756 entitled METHOD AND APPARA-TUS FOR REBUILDING VALVE GUIDES issued August 13, 1974, there is disclosed an insert fabricated from spring-tempered phosphor bronze and a ~g2~

1 method of installing the same. This insert has achieved substantial commercial success and affords, when installed, wear characteristics markedly better than those attained with cast iron. There has been a significant problem, however, with the installation o-f these inserts. The physical characteristics of the insert material, its mode of installation and the rather high cost of the material, more particularly, have dictated that its wall thickness be kept ; as thin as practical. I'hese clictates have resulted, for any given valve stem O.D., in a liner having an installed O.D.
requiring a peculiarly sized reamer or other boring tool to form the passageway within which the insert is to be in-stalled. These reamers are very expensive and, in many cases, mechanics, repairmen and the like have chosen to continue installing the clearly inferior cast iron guides in order to avoid the time and expense involved in the purchase and selec-tion of these peculiarly sized tools.
Simllar problems are encountered where an engine has been previously rebuilt using standard sized toolings.
Removal of the now-worn replacement guide, as will be readily appreciated, leaves little choice but to rebuild with a cast iron or other guide having the same O.D.
The present invention provides an insert which retains the salient features o-f the insert described and claimed in the aforenoted patents. At the same time, however, the inventlon preserves all significant advantages inherent in the prior art cast iron and similar inserts, particularly with respect to avoiding totally the necessity for peculiarly specialized tooling at the installation situs.

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:J109Z919 The present invention provides a multi-layercd insert for lining or relining valve guides of internal combustion engines including separately formed and sub-sequently assembled outer and inner cylindrical tubes or sleeves fitted one within the other. The outer or carrier cylindrical sleeve has a standard outside diameter adapted to substantially match the diameter of a reamed or bored valve guide to be lined or relined, such reaming or boring having been accomplished with standard tools already on hand in virtually all shops. The inner cylindrical sleeve is substantially coterminous with and extends the entire length of the outer sleeve. The inner sleeve also has an outside wall surace slightly larger than the inside wall surface of the outer sleeve and adapted to tightly frictionally engage and be retained within the inside wall sur-face o-f the outer sleeve when inserted therewithi`n. The Inner sleeve also has an inside diameter adapted to receive a valve stem there-through.
In a specific, preferred embodiment of the Pverall invention the outer sleeve or tube is cut and roll fPrmed ~` from sheet stock with the resulting longitudinally extending seam welded and the tube being redrawn to eliminate the weld ~ flash. Alternately, the seam may be left open for later ;~ 25 ~ coDtraction within a reamed valve guide. The outer sleeve may also be foTmed as a seamless, extruded tube in the first instance.

:

~ -4-,~_~,i , 1 Also, in a preferred embodiment of the overall invention, the inner sleeve or tube is also cut and roll formed and includes a longitudinally extending seam. The opposing edges of the seam are tightly abutted against one another to form a substantially seamless tube when that inner sleeve is either inserted within the outer sleeve of the closed and welded or seamless variety, or co~bined with an open seam, outer sleeve and inserted within a valve guide.
The present insert provides significant advantages over prior known valve guide inserts. In addition to the high wear resistance, lubricity and the excellent heat transfer properties in the multi-layered insert as mentioned above, the separate formation and subsequent assembly of the inner and outer sleeves or tubes provide precise and accurate control over dimensions and tolerances such as wall thickness and concentricity for both the individual and combined sleeves or tubes. Such control can be consistently maintained on a high volume basis without costly and time-consuming machining operations being necessary. Such increased control over dimensional tolerances provides the ability to consistently produce inserts which accurately fit the reamed or bored valve guides. Further, it is not necessary to utilize specially sized reamers or boring tools which have been previously necessary to fit irregularly sized inserts.
Standard sized tools may be used with the consistently obtalned tolerances providing an excellent fit for the present insert.
These and other objects, advantages, ~urposes and , ,~

~9 ~

1 :Eeatures of the invention will become more apparent -Erom a study o-f the ollowing description taken in conjunction with the drawings.
B~I:EF DE~sc~IpTIoN OF TH~3 D~AWII~GS
Fig. 1 is a perspective view of a first embodiment of the lnsert -for lining/relining valve guides;
Fig. 2 is an exploded, perspective view o the inner and outer sleev:es or tubes prior to assembly to form the insert shown in Fig. l;
Pig. 3 ls a sectional view of the insert taken along plane III-III of Fig. l;
Fig. 4 is an end view of the insert shown in Figs.
1 and 3;
Fig. 5 is a perspective view of a second embodi-ment of the insert, both the inner and outer tubes having longitudinally extending seams;
Fig. 6 is an end vlew of the insert shown in Fig.
5;
Fig. 7 is an exploded, perspective view of the inner and outer sleeves or tubes of the insert o Figs. 5 and 6 prior to their assembly;
Fig. 8 is a sectional elevation of the inner sleeve or tube being inserted;into the outer sleeve or tube to form an insert such as is shown in Fig. l;
Fig. 9 is a plan view of a blank of metallic material prior to roll forming into an inner or outer tube of the present invention;
Fig. 10 is a block diagram of the steps of the preferred method or manufacturing the insert o the present lnvention;
Fig. 11 is a fragmentary, sectional view o-f the 9~

1 insertion of an insert of the type shown in ~igs. 1-~ into the bored or reamed valve guide of an internal combustion engine; and Fig. 12 is a fragmentary, sectional elevation of the insertion of an insert o-f the type shown in Figs. 5-7 into a bored or reamed valve guide of an internal combustion engine.
DESCRIPTION OP T~IE PREFERR~.D EMBODIMENTS
Referring now to the drawings in greater detail, Figs. 1-4 illustrate a first embodiment 10 of the valve guide insert of the present invention. Insert 10 is a right circular cylindrical tube having multi-layered walls providing the tubes with both high wear resistance and lubricity as well as excellent heat transfer characteristics and strength.
Insert 10 includes a right circular cylindrical outer or carrier sleeve or tube 12 preferably formed from steel (alumi-num has also been utilized and other materials including cast iron may be utilized) and having a predetermined wall thick-ness, concentricity, and inside and outside diameters. Tube or sleeve 12 is preferably roll formed from a precut, planar sheet of steel or aluminum (Fig. 9) into the right circular cylinder such that it includes a longitudinally extending seam 14. Seam 14 may be straight or include an aligning step or ofset as desired. The cylinder is welded at seam 14 and redrawn to elimlnate the resulting flash. The welded tube is therefore a continuous, seamless outer tube within which is fitted the inner tube or sleeve 16. Alternately9 as will be more fully explained below, tube or sleeve 12 may be formed from extruded, seamless tubing of a predetermined wall thickness.
Fitted within tube or sleeve 12 is an inner tube , :
..
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~29~19 1 or sleeve 16 preferably roll formed from a precut blank or planar sheet (Fig. ~ of spring-tempered phosphor bronze metallic material such that it includes a longitudinally or axially extending seam 18 extending its entire length in one portion o its wall. In order to maintain axial alignment of the ends of the tube and also the side edges of the tube which oppose one another across seam 18, a step or o~fset is included in seam 18 including opposing edge portions 19, 20 each of which extend in a plane extending generally transverse to the longitudinal or axial direction of the tube.
Alternately, although not presently preferred, inner sleeve or tube 16 may be formed from extruded, seam-less phosphor bronze tubing of an outside diameter slightly greater than the inside diameter of welded or seamless outer tube or sleeve 12 so that the inner tube or sleeve 16 may be press-fitted into tight, frictional engagement within the outer tube or sleeve 12.
In either case the thickness of the sheet material is chosen such that the O.D. of carrier tube 12 will be such as to fit wlthin a valve guide formed to a stand~rd diameter by a standard sized tool--i.e., 1/2", 5/8", 7/16", etc.
As is seen in Figs. 1-3, the sleeve or tube 16 is press fitted within owter sleeve or ~ube 12 such that it fits coaxially therein with the end surfaces of the two tubes or sleeves being coterminous with one another. A
chamfer or bevel 22 is formed on the inside diameter at one end of the outer sleeve 12 to facilitate insertion by press-fitting of the inner sleeve or tube 16 within the outer sleeve or tube 12 in the manner shown in Fig. 8. Preferably7 the outside diameter and edges at both ends o~ the insert 10 ~9~

1 are cham:fered or beveled at 24 to facilitate insertion of the insert in a valve guide after manu-facture as is shown in Figs. 11 and 12.
The pre-ferred wall thicknesses for insert 10 are -5 approximately 0.0~9 to O.Q80 inches for sleeve 12, depending on the.overall size of the insert~ and approx.imately 0.016 inches for sleeve 16.
The O.D. of the Einished insert 10 shbuld exceed the diameter of the reamed passageway in wllich it is to be installed by approximately 0.0015-0.002 inches to insure a prope.r press-fit. The O,D. of the phosphor bronze liner 16 (when circumferentially compressed), similarly should exceed the I.D. of carrier tube 12 by approximately 0.002 inches to insure'its positive retention in the carrier tube.
Thus, where the guide'is to be reamed with a one-half inch reamer or other tool (typical), the O.D. of the composite liner should be 0.5015-0.502 inches.
Insertion of inner tube or sleeve 16 within outer tube or sleeve 12 causes con~raction or compression o-f the inner sleeve or tube closing seam 18 tightly such that the side~edges of the roll formed blank press tightly against and abut one another. The inner tube or sleeve is thus substantially and effectively seamless after insertion as shown in Figs. 3 and 4. A spiral groove 26 knurling or ~he like may be formed on the inside surface o-f the inner tube 16 after insertion wlthi'n the outer tube by machining such as knurling or the like. The machining forces the inner tube out~ardl~ against t.he outer tube to facilitat.e fric-: tional retent:ion of the' inner tube within the'outer tube.
:: 30 Alternatel'y, machining of the groove or knurling may be performed prior to roll: forming of the' planar blanks of . ~

1~)9;;~919 1 material into the right cylindrical cyli,nders.
Finally, the I.D. of the composite'line 10 may be finished after installation to match closely the'diameter of the valve stem it is to carry. This is particularly advan-tageous since valve stem diameters for a nominal size often vary as much as Q.QQ5 lnche's depending upon the particular manufacturer and extent of use.
Referring now to Figs. 5-7, a second embodiment 30 of the insert -for lining and relining valve guides is illustrated including an outer sleeve 32 roll formed from a blank or planar sheet of aluminum or steel into a right circular,cylinder. Sleeve 32 includes a longitudinally extending seam 34 formed by the side edges of the precut blan~ or she~et being axially and radially aligned with one another but slightly spaced apart circumferentially. In order to prevent axial misalignment of the side edges across seam 34, a step or offset formed by transversely extending edges 36, 38 is provided at at least one position ~ along the seam 34. Instead of closing and welding outer tube 32 as is done with tube 12 in insert embodiment 10, the outer sleeve is left~with an open seam to be closed later upon pTess-fitting within the valve guide of an internal combustion engine.
The inner right circular cylinder 40 is also ~; 25 ~ preferably roll ormed but from a blank or precut sheet of phosphor bronze of a predet~ermined thickness. Sleeve 40 includes a longitudinally extending seam 42 formed by the circumferentially spaced, aligned side edges of the roll ; ' formed blank. Seam 42 also includes transversely extending, opposing edge portions 44, 46 in at least one portion along its length'to pre~ent axial misalignment of the' side edges '' -lQ-10~'~9~19 l which form the walls of the tube or sleeve.
As is best seen in Figs. 5 and 6, inner tube or sleeve 40 is inserted within outer tube or sleeve 32 with seams 34, 42 respectively being~ left open. Seams 34, 42 need not be in any special relationship to one another because both wi'll be tightly closed when insert 30 is posi-tioned in a valve guide ~s in Pig. 12. Thus khe seams may be in registry, spaced 180 apart or at any position in between without affecting the' ultimate'operation of the insert. Frictional engagement between the tubes or sleeves holds them together until they are'inserted in an internal combustion engine valve guide in the manner shown in ~ig. 12 utilizing a special insertion tool having a tapered opening ~hich substan~iall~ matches the bored or reamed size of the valve guide. Insertion in the valve guide compresses or closes' both of the seams 34, 42 in the outer and inner sleeves so that the sleeves become essentially seamless a~ter insertion to prevent loss of oil or abnormal wear. '~n this case, the spiral groove, knurling, or broaching opera-tion to provide an oil-retaining groove or the like within the inner sleeve is performed after insertion in the valve guide. Alternately, the blank or sheet phosphor bronze material may be grooved or knurled prior to roll forming into the right circular cylinder.
As an example of the diameters of the sleeves or - tubes 32, 40 of insert 30, for a one-hal-f inch valve guide bore, auter sleeve or tube 32 has a maximum uncompressed or free diamet'er of 0.562 inches. In its -free state, the inner sleeve or tube, before insertion in the' outer sleeve is 0.432 inches'. ~hen the' seams 34 and 42 are closed, the outer slee`ve or tube~has-a diameter of 0.5Q2 inches designed ~o~z9~

1 to be press-fitted into an 0.500'inch bore or valve guide.
The inside diameter of the outer sleeve or tube 32 in its free state is 0.401 inches. These dimensions include tolerances for spring back after forming and before pressing into the cylinder head of the internal combustion engine.
The preferred wall thicknesses for insert 30 are the same as those discussed in connection with insert 10.
Like insert 10, the end outer diameter edges of outer sleeve 32 may be chamfered or beveled at 31 to facili-tate insertion in the valve'guide. At least one inner end edge of sleeve 32 may also be chamfered or beveled to facilitate insertion of inner sleeve or tube 40.
Referring now to Figs. 8-10, the preferred embodi-ments 10 and 30 of the valve guide insert both include inner and outer sleeves or tubes pre-ferably formed from flat metallic sheet stock of appropriate desired thickness, precut or fashioned into a blank as shown in Fig. ~. The side edges of the blank, insofar as liners 16 and 40 are concerned, are preferably precut to include the trans~erse edge portions which prevent axial misalignment in the finished cylindrical tubes. The thickness of the blank is ' chosen for the desired wall thicknes's of the finished tube or sleeve. The widths of the blanks for sleeves 12 and 32 or 16 and 40 ? denoted as dimension "A" in Fig. 9 7 are selected to effect a tight, press-fitted engagement with the reamed or bored valve guide being repaired or the inside surface~of the outer sleeves, respectively9 after rolling and when the seams of the resulting right circular cylinders are closed.
Each blank is formed by conventional progressive rolling to its desired diameter depending on wll'e'ther it will ~ ~ 2 ~ 1~

1 be used -Eor an inner or outer sleeve or tube. Such rolling allows the concentricity of the' tubes being formed to be precisely and accurately controlled while the wall thickness of the res'ulting tube or sleeve is maintained because of the uniform thic~ness ~of the precut blank.
In the case o-f sleeve'or tube 12 shown in Figs. 1-4, whi'ch is preferably roll -formed from sheet steel, the side edges' of the rolled blank are'axially and radially aligned, abutted together, and welded by el0ctrical resist-ance welding along the resulting butt joint to form a closed, seamles's tube. Therea-fter, the closed, seamless~
welded tube is redrawn to remove any wel'ding flash and to obtain the ~rue desired diameter for the outer ~ube. The inside wall surfaces of the outer tube are finish machined to the proper size designed to receive the inner sleeve or tube~, after which ~he ou~er tube is cut to length and chamfered or beveled on its outer diameter end edges and at least one of its inner diameter end edges. The outside diameter of the outer tube is then centerless ground to the exact desired size for insertion into the reamed or bored valve~guide being repaired.~
In the case of outer sleeve or tube 32, the blank of materiaI shown in Fig. 9 preferably either steel or aluminum is roll formed to the desired diameter but the seam between the opposing, aligned side edges is left open. The inner sleeve or tubes 16 or 40, formed from sheet phosphor bronze material of desired ~all thickness for the inner tubes, are roll -formed in the same manner as outer sleeve 32 with their se-ams 18, 42 being left open.
After ormation of the inner and outer sleeves or tubes,~the'two are assembled together in slightly differing ~O~

l manners depending on embodiment 10 or 30. Insert 10 is asse~nbled as shown in Fig. 8 wherein the outer closed seamless or welded tube 12 is positioned in an upstanding manner in a fixture 50 on a supporting sur-face. A cylin-drical, hbllow insertion tool ti2 is positioned on the top end ~dge of sleeve 12 such that its lowermost inside diameter is coaxial with and aligned with the inside diameter of sleeve 12. The inside diameter o:~ tool 52 is equal to or slightly less than that of sleeve or tube 12. The upper end of the tool 52 tapers at 54 to the desired inside diameter of the inner sleeve 12 such that the inner sleeve or tube 16 or 40 can be easily inserted in its expanded, free state in the upper end and driven downwardly to compress and contract the size of the inner tube and inserted or press-fitted within the outer sleeve or tube 12. Such insertion or press-fitting is accomplished by driving sleeve 16 through ;~ tool 52 with a shouldered cylindrical ~ool 56 located in the upper free end of inner sleeve 16. Tool 52 has a length at ; least as long as the length of sleeve 16 for fully supporting ~20~ the relatively thin side ~alls of sleeve 16 during such insertion. Sleeve 16 is driven completely through tool 52 into place within sleeve l2 such that it is coterminous and aligned therewith.
In the case of the assembly of insert 30, tool 52 as explained above may also be used; however, because outer sleeve or tube 32 is expandable because of the open seam 34, inner tube or sleeve 4Q may be more easily pressed or fitted within outer sleeve 32 since tight, gripping frictional engagement of the two tubes does not result until the insert 30 is in place within the cylinder`head.
Following press~-fitting of the tubes` 12 and 16 -14~

~9:;~9~9 1 together for insert 10, the inside wall sur~ace of the inner tube 16 is spiral rolled or knurled to provide an oil-retaining groove to -facilitate lubrication o-f the valve stem when inserted therethrough in the cylinder head. Such spiral rolling or knurling which may also be accomplished by ball broaching or othe~ machining operation, also forces or expands the inner tube outwardly against the outer sleeve or tube to facilitate frictional engagement and retention of the tubes within one another to prevent separation of the tubes when in use. Altho'ugh this latter step' may also be performed after tubes 32 and 40 are assembled together, it more pre-ferably is accomplished after insertion of insert 30 in the cylinder head. Alternatively, the blanks as shown in Fig. 9 from which the inner and outer sleeves or tubes are roll formed, may be knurled or grooved prior to rolling.
After assembly in the above manner, inserts 10 or 30 are inserted in the bored or reamed valve guides being repaired as shown in Figs. 11 and 12. In the case o-f insert I0, one of the chamfered ends of insert 10 is placed against a valve guide 60 to be repaired which has been previously reamed or bored to a standard diameter. Thereafter, a driving tool 58 having a shoulder at one end and a cylin-drical locating projection coaxial therewith is placed over the end of insert 10 (Fig. llj and the insert is driven into :: :
~25 place within the bored or reamed valve guide. ~ecause insert 10 is completely closed and compressed to its ultimate outside diameter, it is not necessary to use any tapering insert tool 52 or to support the side walls of insert 10 during such insertion.
Howe'~er, in the' case'of insert 30 as shown in Fig.
12, both'the' outside tube 32 and the inner tube or sleeve ~9 2 ~ ~

1 40 are in an expanded condition larger than their u]timate sizes when inserted in the valve guide 60'. In such case, when using insert 30, an insert tool 62 having one end matching or slightly smaller than the desired inside dia-meter of the valve guide 60' is placed ato-p the valve guide while the other end includes a taper 6~ allowing easy insertion of the expanded insert 3Q but narrowing to the desired diameter at the lower end. A tool 58 having a standard diametçr equivalent to the inside diameter of guide 60' and the lower end of to~l 62 is used to drive insert 30 through insert tool 62 into the valve guide. Tool 62 thus compresses or contracts both the inner and outer sleeves during such insertion to their final, ultimate diameters wherein seams 34, 42 are closed tightly to -form a substantially seamless insert as in the-case of insert-10 which is completed prior to assembly in the valve guide. Tool 62 preferably has a length at least as long as insert 30 so as to provide ~ ~ support or the side walls of the insert during such insertion ; in the valve guide 60'. After insertion of the inserts 10 and 30 as shown in Figs. 11 and 12, slight finishing, boring, or reaming of the inside diameter to assure matching to the diameter of the valve stem fitted therethrough may be necessary. This is particularly true when the lnsert has been shlpped in "unsized" condition so that minor variations in valve stem diameter may be accommodated in the field.
The inserts may either be~finished in specified lengths which have been preselected to match the engine being overhauled or manufactured, or may be cut off after install-ation by stanclard techni~ues.
After such insertion of either insert 10 or 30, the valve stem of the poppet valve may be inserted through 1 the inside diameter of the insert and the remainder of the valve train assembled on the cylinder head. As with insert 10, insert 30 in its compressed state has an outside diameter slightly greater than the inside diameter o~ valve guide 60' S so as to be tightly press-fitted therewith and to stay in place during use.
The present invention, therefore, provides a valve guide insert for lining or relining during repair of worn valve guides including multi-layered walls, the interior o which is highly wear resistant and self-lubricating or lubricious because of the use of phosphor bronze, and the exterior of which is size accommodated to standard diameter tools. Other materials having these qualities may also be used. The outer tube or sleeve provides strength and support for the inner sleeve or tube. Not only does the separate formation and subsequent assembly of the two different types of inner and outer sleeves or tubes result in the above advantages but also importantly allows accurate and precise control of dimensionaI tolerances for the insert including wall thickness, concentricity inside and outside diameters and the like. Finally, because such outside diameters can be so precisely controlled, standard sized reaming and boring tools used to prepare the valve guides for insertion of the insert may be used.
~ While several forms of the lnvention have been shown and described, other forms wlll now be apparent to those skilled in the art. Therefore, it will be understood that the embodiments shown in the drawings and described above are merely for illustrative purposes, and are not intended to limit the scope of the invention which is defined by the claims which follow.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

A valve guide insert for lining and relining the entire length of a valve guide of an internal combustion engine comprising an outer, metallic, cylindrical sleeve having an outside diameter adapted to be press-fitted within a valve guide and an inside diameter adapted to receive an inner sleeve; and a separate, wear-resistant, metallic, inner cylindrical sleeve located concentrically within, being substantially coterminous with, and extending the entire length of said outer sleeve, the metal of said inner sleeve being dissimilar to that of said outer sleeve, said inner sleeve having an outside diameter slightly larger than said inside diameter of said outer sleeve before insertion in the outer sleeve such that the outside wall surface of said inner sleeve tightly, frictionally engages the slightly smaller, inside wall surface of said outer sleeve after insertion to positively retain said sleeves together, said inner sleeve having an inside diameter adapted to receive a valve stem therethrough whereby the separate formation and subsequent assembly of said inner and outer sleeves allows precise control of tolerances, wall thicknesses and con-centricities of said insert and provides strength, wear-resistance, and an outer diameter adapted for installation with standard size, commonly available installation tools.

The insert of claim 1 wherein said outer sleeve is formed from a metallic material having excellent heat transfer qualities such as steel or aluminum; said inner sleeve being formed from a material having high wear resistance and lubricity such as phosphor bronze.

The insert of claim 1 wherein said outer sleeve is a cylinder cut and roll formed from a sheet of metal having the desired ultimate wall thickness for said outer sleeve and opposing side edges along a longitudinally extending seam in one wall of said outer sleeve, said opposing side edges of said outer sleeve being radially and axially aligned with and abutting one another along said seam, said side edges being spaced slightly apart across said seam after forming to allow compression and contraction of said sleeve for a tight engagement with a valve guide when the insert is inserted therein and sub-stantially seamless after such insertion.

The insert of claim 3 wherein said inner sleeve is a cylinder cut and roll formed from a sheet of metal having the desired ultimate wall thickness for said inner sleeve and opposing side edges along a longitudinally extending seam in one wall of said inner sleeve, said side edges of said inner sleeve being radially and axially aligned with and abutting one another along said seam, said side edges also being spaced slightly apart across said seam after forming to allow compression and contraction of said sleeve for a tight engagement with the inside of said outer sleeve when inserted therein and substantially seam-less within said outer sleeve after insertion.

The insert of claim 4 wherein the side edges of at least one of said inner and outer sleeves include adjacent transverse edge portions opposing one another across said seam and extending in planes generally perpendicular to the axial direction of said sleeve to prevent axial misalignment of said side edges.

The insert of claim 5 wherein the side edges of both of said inner and outer sleeves include said adjacent, opposing transverse edge portions.

The insert of claim 4 wherein the inside surface of said inner sleeve includes a spiral groove to aid reten-tion of lubricating oil therein for the valve stem when the stem is inserted through the sleeve.

The insert of claim 4 wherein said outer sleeve includes a chamfer on its outside diameter at at least one end thereof to aid insertion in a valve guide to be relined as well as a chamfer on its inside diameter at at least one end thereof to aid insertion of said inner sleeve.

The insertion of claim 1 wherein said outer sleeve is a cylindrical tube formed from a blank cut from a sheet of metallic material having the desired ultimate wall thickness for said outer sleeve, said tube including a welded seam extending longitudinally along its side wall where the side edges of said blank are welded together after being aligned and abutted against one another.

The insert of claim 9 wherein said inner sleeve is a cylinder cut and roll formed from a sheet of metal having the desired ultimate wall thickness for said inner sleeve and opposing side edges along a longitudinally extending seam in one wall of said inner sleeve, said inner sleeve tightly frictionally engaging the inside surface of said outer tube such that the side edges of said inner sleeve seam are aligned with and abut one another whereby said inner sleeve is substantially seamless within said outer tube.

The insert of claim 1 wherein said outer sleeve is a closed tube having continuous side walls; said inner sleeve is a cylinder cut and roll formed from a sheet of metal having the desired ultimate wall thickness for said inner sleeve and opposing side edges along a longitudi-nally extending seam in one wall of said inner sleeve, said inner sleeve tightly frictionally engaging the inside surface of said outer tube such that the side edges of said inner sleeve seam are aligned with and abut one another whereby said inner sleeve is substantially seamless within said outer tube.

The insert claim of claim 1 wherein the outer diameter of said outer cylindrical sleeve is slightly larger than the diameter of a standard-size boring tool whereby the insert is adapted to be force fitted within a valve guide which has been sized by such a standard-size boring tool.

The insert of claim 1 wherein said outer cylindrical, metallic sleeve is a tube having inside and outside wall surfaces and inside and outside diameters; said inner, cylindrical, metallic sleeve being a tube formed from phosphor bronze and having inside and outside wall surfaces;
said inner, phospher bronze tube being significantly thinner than said outer metallic tube, having a wall thickness less than one half the wall thickness of said first tube; and said inner tube located coaxially within said outer tube.

The insert of claim 13 wherein said inside wall surface of said inner tube includes a machined groove formed after insertion of said inner tube within said outer tube so as to force said inner tube outwardly against said inside wall surface of said outer tube to help retain said tubes together.

The insert of claim 1 wherein said outer sleeve is a closed, continuous tube formed from a metallic material having high heat transfer qualities such as steel or aluminum and including a welded seam extending longitudinally along its side wall; said inner sleeve being a tube formed from a metallic material which is highly wear-resistant and lubricious such as phosphor bronze, and being preformed with a length equivalent to that of said outer tube, said inner tube also having opposing side edges along a longitudinally extending seam in one wall of said inner tube, said inner tube tightly, frictionally engaging the inside surface of said outer tube such that the side edges of said inner tube seam are compressed together and aligned with and abut one another whereby said inner tube is substantially seamless within said outer tube whereby said insert is strong, longwearing and provides improved heat transfer characteristics.