HIGH-PERFORMANCEIn the serious performance community, there’s moreto intake and exhaust valves than meets the eye.Thanks to the technological advancements madewithin the racing components industry, today we have a mind-boggling array of choices. In this arti-cle, we attempt to explain various materials and de-signs in an effort to better understand today’s valve offerings.Stainless-Steel Valves.Although stainless-steel valves may be offered in varying grades and alloy recipes, high-performance stainless-steel valves are most commonly made of material referred to as EV8 (a more expensive heavy-duty stainless alloy material), and are made from a one-piece forging. In addition, some valve makers offer a stronger stainless-steel formula that offers higher heat re-sistance. Some makers use EV8 only for their exhaust valves, while others utilize this material for both intake and exhaust valves.High-quality performance stainless valves should fea-ture hard stellite tips (since stainless is not hardenable, a hardened tip must be welded onto the stem) and hard chrome-plated stems (not cheap flash chroming) to re-duce guide wear. Undercut stems contribute to a slight weight reduction and benefit flow characteristics. Note : If a particular brand of stainless-steel valves does not fea-ture a hard tip, the use of lash caps will be required.Titanium Valves.Titanium offers the highest strength-to-weight ratio of any known metal. In an unal-loyed condition, titanium is as strong as some steel mate-rials but about 45% lighter. When used to manufacture automotive valves, titanium is alloyed with small percent-ages of various materials, including copper and molybde-num. Titanium can be challenging to machine, as it can gall if tooling isn’t hard and sharp enough, and if the ma-terial isn’t cooled properly during machining.Many titanium valves are produced by starting with a forging, then machined to final shape. But some are pro-duced using a two-piece inertia-welded design. According to Xceldyne Technologies, this process is so effective that inertia-welded valves have been certified as having a su-perior grain structure than a one-piece forged design.The valve is then CNC-machined and in many cases un-dercut in the stem area to allow a bed for the inlay of a coating. The valve is then plasma moly-coated.Specific sections of the valve are further machined and the stem is ground, leaving the plasma moly coating over only the desired stem area. The head, stem and keeper grooves are then final-machined. Stem grinding is finalized to establish dimensional tolerance to within .0002 in. A final precision-polishing reduces the potential for carbon buildup.B YJ IM G IBSONV AL VESThis photo shows a sampling of titanium valves in blank form. Stems have been machined to near-final diameter and the heads are rough-formed, prior to CNC machining.P h o t o c o u r t e s y X c e l d y n e T e c h n o l o g i e sThree styles of valve tips are gener-ally available, which include a hard-ened steel tip or a ceramic-coated tip (ceramic tips are to be used in con-junction with lash caps) and thin-film technology such as a plasma vapor deposition (PVD) coating.Since titanium is a relatively soft material, it requires a protective con-tact surface at the stem tips, usually hardened lash caps. Xceldyne noted that when valves feature stem diame-ters smaller than 5⁄16in. (7mm or less),a specialized hard coating is applied to the stem tip to protect it from lash cap friction.The durable, hard ceramic coating is intended to protect the titanium from the friction caused by the lash cap. Other coatings such as a PVD treatment, a chromium nitride treat-ment, chemical vapor deposition (CVD), diamond-like carbon (DLC)or other highly specialized protective application may be applied to the tips. This hardened feature at the tip prevents material transfer or galling between the tip and lash cap.Hollow titanium valves are also available, either with hollow stems or with a combination of hollow stems and hollow heads. Hollow-stem de-signs reduce valve weight by about10%. The hollow-head design is a proprietary process that removes an additional 6 to 8 grams of weight (de-pending on valve size). As part of the proprietary process, the inside of the valve head may be reinforced to pro-vide a support structure for strength and rigidity.The following precautions should be taken during the handling and use of titanium valves:•Do not touch the valve surface with your bare hands, since finger-print acids may affect the e gloves or coat the valve with oil before handling.•Never use a lapping compound or any abrasive material when the valve is coated with a PVD-style coating.•Replace valve seats during each and every rebuild to ensure a proper valve-to-seat contact. The width of the contact zone (valve face to valve seat) should be at least 1mm.•New valve seats should be a rela-tively soft material, such as bronze or nodular iron (heat-treated to Rock-well RC32 or less).•Unless directed otherwise by the valve maker, always use hardened lash caps on titanium valves. Some makers offer valves built with friction-welded hardened tips. Bare, unprotected titanium tips will mush-room when exposed to rocker arm forces.If the titanium valve features a stellite tip, the tips can be ground dur-ing valve service, but with caution . You should be able to safely remove a maximum of approxi-mately .015 to .020 in.As far as valve seats are concerned, tradi-tional cast or hard seats can wear a groove intothe valve face, so a nick-el-bronze seat material is recommended. Other exotic-metal seats are al-so available.Titanium valves are designed for ap-plications where valve train weight needs to be reduced, for high-rpm and extended high-rpm applications, since titanium valves allow for higher engine speeds and will accommodate highly aggressive camshaft profiles. However,for extreme-temperature situations (blown, turbo and nitro engines), titani-um may not be the ideal choice. Also,for many street applications, titanium may not be a good choice for an engine that doesn’t need to rev as highly, or for an engine that will be buttoned up and not torn down and serviced regularly.In other words, it’s probably best to re-serve the use of titanium for naturally aspirated race or inlet-side forced-induction applications where valve train weight and sustained high-rpm use is paramount.Inconel Valves.Inconel is a regis-tered trademark of Special Metals Corp., and refers to a family of nickel-based superalloys . Inconel alloys are ox-idation- and corrosion-resistant materi-als designed for use in high-heat envi-ronments. Inconel retains strength over a wide range of operating temperatures.As opposed to steel or aluminum,it doesn’t creep as much (change dimen-A variety of specialty coating s can be applied to valves to enhance spe-cific properties such as lubricity,resistance to wear and thermal per-formance to heads, stems or tips.The Pro Stock titanium valve on the left features aPVD-applied diamond-like coating (DLC) for ex-treme hardness and reduction of friction. The Formula 1 titanium valve on the rig ht features a DLC coating on the stem area for a combination of guide wear protection and friction reduction.P h o t o c o u r t e s y X c e l d y n e T e c h n o l o g i e sP h o t o s : J i m G i b s o nsion) under high-heat use.Inconel alloy makeup can include during valve opening cause the liquidsodium to migrate upward inside theHollow-Stem Valves.Hollow-stem stainless-steel or titanium valvesThey may look the same but not all parts are createdequal. Delphi fuel pumps deliver fast-pressure risefor quick engine starts and feature an integrated OEfuel vapor pressure sensor and two-strainer systemfor long-lasting durab ility. What does that mean?Reliab le fuel pumps you, and your customers, cantrust. Providing you with the benefi t of more than 100years of OE heritage, we are the company that makesthe parts cars are born with.High standards.Below the surface.Delphi fuel pumps.IT’S WHAT’S UNDERNEATH THAT SETS DELPHI APARTDelphi Fuel Module // A Integrated Fuel PressureRegulator (1) Maintains pressure at fuel rail (2) Negatesfuel return reducing vehicle EVAP emissions; B Quieter OETurbine Pump Performance matched to OE specifi cationsand lower noise levels – 5 to 10 dB lower – in the cockpit./am©2011 Delphi Automotive Systems, LLC. All rights reserved.ABCircle #2810% as compared to a comparable solid-stem valve.GeneralRecommendationsFor most street engines, a quality stainless-steel valve is recommended.Titanium is generally preferred for most race applications, but some en-gine builders that specialize in tur-bocharged applications prefer a high-nickel Inconel valve. Hollow-stem valves tend to work great on the in-take side, but are much more difficult to manufacture and to inspect for de-fects on the I.D. surface. Many up-per-echelon engine builders shy away from hollow valves for that reason inendurance (NASCAR or 24-hour style) racing.Stainless-steel valves are most com-mon in street and mild-performance racing. Titanium is used when valve weight is important and cost is not a consideration. Inconel is used when exhaust gas temperatures get really high. Stainless steel (for street perfor-mance) has much better durability characteristics than titanium, and the street guys won’t usually see the real benefits of titanium. In racing, use ti-tanium when you want to lose weight…and spend a lot of money.If durability is your customer’s con-cern and he’s already making as much power as he wants and is already turning the engine as high as he wants, then use a stainless-steel mate-rial. If he’s running nitromethane,then an Inconel exhaust valve materi-al will be his best bet if he wants to finish a race.On the exhaust side, sodium-filling is the best way to increase the head capacity of a hollow exhaust valve. Ifstock diameter steel valves are re-Applying a hard coating such as titanium nitride to the stem tip and lock groove (left) protects the titanium valve material from galling damage from a lash cap and retainer locks. Coating the valve face (right) adds protection from heat and deposit buildup to that area.Performance Valve ManufacturersComp Cams Crane Cams, Del West Engineering, Electronic Chrome & Grinding Elgin Industries Ferrea Racing Components KPMI (Kibblewhite Precision Machining) Manley Performance Products Milodon, Inc. Pioneer, Inc. Racing Engine Valves RPM International, SI ValvesSupertech Performance, Xceldyne Technologies Zanzi Spaquired, but a valve weight is not man-dated, going to a hollow intake and only a single groove because it forcesthe lock to grip the valve stem andin the locks, which is fine for streetand low-end performance. BecauseThey may look the same b ut not all parts are created equal. Delphi OE CVCcompressors have proven warranty experience of less than 1 Incident Per ThousandVehicles (IPTV) on major OEM applications. What does that mean? Reliable, highperformance compressors you, and your customers, can trust. Providing you withthe benefi t of more than 100 years of OE heritage, we are the company that makesthe parts cars are born with./amHigh standards.Below the surface.Delphi CVC compressors.ABIT’S WHAT’S UNDERNEATH THAT SETS DELPHI APARTDelphi C C Compressor // A Swash Plate ariableMechanism Patented technology adaptab le to pneumatic andelectronic control for high speed operation at up to 9200 RPM;B Integrated Control Valve Compact packaging and four-port fl owdesign provides a wider range of control set points for improvedfuel economy and emissions.©2011 Delphi Automotive Systems, LLC. All rights reserved.Circle #29。
