CYLIN­DER HEAD TECH

Diesel World - - Tractor Talk 1962 John Deere 3010 -

The diesel en­gines of to­day are quite ad­vanced com­pared to those first found in farm and com­mer­cial equip­ment from decades ago, with elec­tron­i­cally con­trolled in­jec­tion events, high­pres­sure in­jec­tion pumps and vari­able-ge­om­e­try tur­bocharg­ers. It seems fed­eral stan­dards for cleaner emis­sions is re­ally what drives the OEMS now, but lucky for us big­ger horse­power and torque num­bers keep com­ing year af­ter year. While the mo­tors of to­day have some ex­cel­lent tech­nol­ogy and parts inside them, there is al­ways room for im­prove­ment when it comes to ab­so­lute peak per­for­mance. Just like in the gas en­gine mar­ket, cus­tom cylin­der heads are still one of the best ways to find hid­den po­ten­tial within the Duramax, Cummins and Power Stroke en­gines.

Turn­ing to the crew at In­dus­trial In­jec­tion for a lit­tle in­sight on af­ter­mar­ket cylin­der head tech­nol­ogy, we can get a lit­tle info on just how in-depth diesel cylin­der head ma­chin­ing can go. In­dus­trial In­jec­tion of­fers street and com­pe­ti­tion ori­ented cylin­der heads based on what a par­tic­u­lar ap­pli­ca­tion needs to at­tain a spe­cific horse­power goal. There are a few ma­jor changes made to im­prove the cylin­der head po­ten­tial for both stock and mod­i­fied en­gines.

Port­ing of the in­take and ex­haust run­ners, per­for­mance valves and high­rev valve springs are the ones we all ex­pect, but there are other up­grades that can fur­ther en­hance a head’s dura­bil­ity and po­ten­tial un­der the most ex­treme con­di­tions.

Heads that are cleaned up and pass the crack and pres­sure tests can start the ma­chin­ing and assem­bly process. To al­low com­plete ac­cess to the in­take and ex­haust port run­ners, valve guides and valve seats are re­moved. Through years of test­ing flow pat­terns on a flow bench, master port­ing di­men­sions and CNC pro­grams were writ­ten to bring the cylin­der head to max­i­mum flow po­ten­tial with­out sac­ri­fic­ing dura­bil­ity. The cylin­der ports’ wall thick­ness has to be taken into con­sid­er­a­tion if dura­bil­ity is a con­cern, as port­ing too thin can lead to pre­ma­ture fail­ure. This is es­pe­cially true in a diesel, which ex­pe­ri­ences such a large heat ab­sorp­tion and tem­per­a­ture change in such short amounts of time.

On a 5-axis CNC ma­chine built specif­i­cally for cylin­der head port­ing, state-of-the-art CAD/CAM soft­ware runs through each in­take and ex­haust run­ner for a lengthy ma­chin­ing process. An­gles and smooth­ness of the bore are done to ex­act­ing spec­i­fi­ca­tions to en­sure proper air dis­tri­bu­tion to the valve, which will help with over­all flow and make for a more use­ful power band. Af­ter the port match work is com­pleted, ma­chine work be­gins on the valves and other ar­eas of the head. New high-strength, iron-based al­loy guides can be in­stalled, which are heat treated for un­par­al­leled dura­bil­ity and wear re­sis­tance. The new valve guides also of­fer a spi­ral groove on the inside bore that aids in oil­ing and lu­bri­ca­tion of the valve while the en­gine is op­er­at­ing.

The cylin­der head will then get new valve seats made from a nickel-based, non-mag­netic ma­te­rial. These valve seats were de­vel­oped to per­form un­der the most ex­treme con­di­tions and are ex­tremely re­silient to heat stress frac­tures and crack­ing. Drop­ping a valve seat in a brand-new en­gine is not some­thing you want to be con­cerned about, and these seats have proven them­selves in plenty of en­gines sold by In­dus­trial In­jec­tion. The valve seats re­ceive full multi-an­gle ma­chin­ing to max­i­mize air­flow in and out of the cylin­der head.

At this point, the mat­ing sur­face of the cylin­der head can be ma­chined and milled us­ing CBN or di­a­mond tool­ing de­pend­ing on the sur­face fin­ish re­quired by the cho­sen head gas­ket. De­pend­ing on the ap­pli­ca­tion, the cylin­der head may also be ma­chined for fire rings, which places a small ma­chined ring groove around each com­bus­tion cham­ber. This is ex­tremely com­mon on both the 12-valve and 24-valve Cummins heads, as fire ring gas­ket kits have proven to be the most re­li­able way to seal a cylin­der head to the en­gine block in high-per­for­mance and high-boost ap­pli­ca­tions. Some cylin­der heads will also have the freeze plug ports drilled and tapped for threaded in­serts, which will re­place the fac­tory-style pressed-in plugs. Once all the ma­chin­ing has been com­pleted, the cylin­der heads will un­dergo one last wash and the fi­nal assem­bly can be done. New valves and high-rev valve springs with ti­ta­nium keep­ers can be in­stalled as well.

 This 24v cylin­der head is be­ing prepped for in­stal­la­tion on a fully built com­pe­ti­tion 6.7L Cummins short block. In­dus­trial In­jec­tion’s com­pe­ti­tion head in­cludes full CNC port­ing on the in­take and ex­haust, new valves, guides, per­for­mance valve springs and fire ring head gas­ket grooves. The fac­tory in­take man­i­fold is also ma­chined off, leav­ing a flat milled sur­face that is drilled and tapped to ac­cept an af­ter­mar­ket high-flow man­i­fold.

 On the Street Duramax heads, ad­di­tional ma­chine work is done around the valves. This is re­ferred to as an “un­shrouded valve.” Since most diesel en­gine cylin­der heads have the valve face re­cessed from the deck sur­face to al­low for proper pis­ton clear­ance, the amount of time the valve is open and the amount of air that can be passed through it is af­fected. Ma­chin­ing small grooves around the valves gives the air that much more area to travel through be­fore the valve is fully closed. You’ll also no­tice the groove doesn’t go all the way around the valve, as this por­tion gets too close to the outer cylin­der wall and could cause is­sues with the head’s seal­ing sur­face with the en­gine block.

 Be­cause of the 5-axis CNC ma­chine and CAD/CAM soft­ware de­signed specif­i­cally for cylin­der head port­ing, the in­take run­ners on the Duramax cylin­der heads are nearly per­fect ev­ery time. The smooth in­ter­nal bores and match­ing pro­files elim­i­nate re­stric­tion in the air stream’s path and will help with over­all en­gine ef­fi­ciency. The cylin­der head port­ing should also help in­crease tur­bocharger per­for­mance, es­pe­cially when paired with the right camshaft pro­file that will al­low the valves to open and close at the ex­act mo­ment they are needed to.

 This cut­away of a Com­pe­ti­tion Se­ries 12-valve cylin­der head shows the in­take run­ner’s path. If you look at the wa­ter jacket path­way on the right, you can see how im­per­a­tive it is that the port­ing job be done cor­rectly. If the port work is taken too deep, that di­vid­ing wall can be­come too thin and will be more likely to crack and leak, at which point the head would be un­re­pairable and needs to be re­placed.

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