Head Porting

8/2/2019 Head Porting

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Once your porting project turns to that, you're beyondthe scope of basic porting techniques.

Why is basic port work important to your engine's

performance? It reduces the restriction in the engine'sintake and exhaust tracts. Reduce that restriction andyou let more air into the cylinders. If you have more air,you can add more fuel.The result is increasedhorsepower.

Most of the work in a basic porting project is focused onreducing those restrictions which are caused by: 1)"steps" that may obstruct intake air flow as it transitionsfrom the intake manifold to a smaller intake port entry inthe head; 2) casting bumps, ridges or other marks, suchas those you may find on port floors or roofs; 3) sharpedges, such as those you will find around the valve

guide bosses at the top of the valve pockets; and 4) thepoint where the intake port floor curves down to thevalve seat.

Basic porting, while somewhat time consuming, is nothard work. It takes about 10-12 hours to do a set ofaverage V8 heads. Some week nights and a weekendinvested in your heads and your basic porting projectwill be complete.

Time is money, so we are not going to tell you doingyour own heads will save a lot; however, mostprofessional cylinder head porting businesses will

Basic Cyl inder Head Por t ing 1

2006 Standard Abrasive

Basic Porting Will

Improve YourEnginesPerformance.

Basic cylinder headporting will improvethe performance ofany productioncylinder head byremoving flaws thatcome through massproduction. Basicporting does notattempt to correctany design orengineering deficiencies.

Here's an interesting head porting fact: In many cases, the greatestperformance gain per dollar spent comes upon application of basicporting procedures to a production cylinder head.

These basics can be done by any do-it-yourselfer, even those with noporting experience, using the Deluxe Porting Kit and the GasketRemoval Kit (part nos. 260001 and 260005) from the StandardAbrasives Motorsports Division, along with a die grinder and somecommon hand tools.

There is a significant difference between basic head porting for a street-high-performance or weekend racer application and the very complexcylinder head work you see in a Pro Stock drag race motor or aNASCAR NEXTEL Cup race engine. Doing full-on race heads requiresthe services of an experienced cylinder head professional, so Pro Stock,NEXTEL Cup and similar heads are best left to experts. Basic headporting, however, is easy...so easy that even beginning hot rodders cando it well.

The area of the valve guide thatprotrudes into the intake orexhaust port is always a placewhere sharp edges andrestriction to flow are found. Abasic porting project seeks tosmooth those sharp edges.

It is easy for the do-it-yourselfer to port cylinder heads.All you need is the Standard Abrasives Deluxe PortingKit, some common tools and some free time.

The components of the Porting Kit areneatly packed in a compartmented box.There are enough abrasive materials to porta set of V8 heads.

D . I . Y .

B a s i c C y l i n d e r H e a d P o r t i n g

A more significant point ofrestriction is where the intake orexhaust port floor curves down tomeet the valve seat. Called the"short side radius," it is also aplace where sharp edges androughness pose a threat to flow. Inthis cutaway of a productioncylinder head, the short sideradius has not one but two verysharp edges.


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powered by motors rated at2.5 horsepower or more willwork well.The air systemshould be equipped with anadjustable pressureregulator.The abrasiveproducts' maximum safespeed is 18,000-20,000rpm. If an air grinder's

maximum rpm exceeds thatyou must reduce the airpressure with the

regulator so that speed isnot exceeded.

While the never-exceedspeed is 18,000-20,000rpm, best durability of theabrasive products isachieved when the grinderruns at 10,000-12,000 rpm.Obviously, measuring thedie grinder's speed isdifficult; however, most toolmanufacturers cite the

maximum speed either in the unit's instructions or on aspecification plate attached to the tool. Supposemaximum speed of your unit is 20,000 rpm, but youwant to run it at 10,000. Operate the grinder at halfthrottle and listen to the noise it makes. Then, run it atfull throttle and adjust the pressure regulator such thatthe noise is about the same as before. That willapproximate 10,000 rpm.

The pressure regulator is important for another reason.You hold a die grinder in both hands, one on the rear ofthe tool and the other on the front of the unit.The fronthand controls the grinder and operates the throttle. It iseasier to manipulate a die grinder with the throttle wideopen than it is to both control the grinder and modulatethe throttle at the same time.

You may be using an electric die grinder. That isacceptable as long as its maximum rpm is below the18,000-20,000 rpm limit. Because electric grinders areoften capable of exceeding that by a significant margin,an electrical device allowing the user to reduce the tool's

speed is necessary. Additionally, speed regulation of anelectric grinder will be necessary if you want to use theabrasives at 10,000-12,000 rpm.

Additional tools and materials required are: A 5/64-in.hex key (Allen wrench), the die grinder's chuckwrenches, a set of the intake manifold gaskets you willuse when you assemble the engine, a set of intakemanifold bolts, a scribe, machinist's bluing (either brush-on or spray-on), a pair of four-inch long 2x4 wood blocksand junk intake and exhaust valves that fit your heads.

None of the techniques used in a basic porting project

charge $400-$600 for what is sometimes known in thetrade as a "street/strip" port/polish job.Your basic portingproject, done with the Standard Abrasives Porting Kit,will allow you to spend that $400-$600 on some otherperformance enhancement you want.

The project is made up of six sub-tasks:

1. Intake port entry enlargement, surface finishingand port matching.

2. Smooth the intake short side radii, valve guidesand valve pockets.

3. Smooth the exhaust short side radii, valveguides and bowls.

4. Exhaust port and bowl polishing.5. Combustion chamber polishing.6. Intake manifold port matching.

Five of these six tasks reduce restriction in the intakeand exhaust tracts. The remaining step, polishing thecombustion chambers, inhibits carbon build-up,decreasing an engine's tendency to detonate or "knock"under heavy load.

After we touch on materials, tools and safetyprecautions, we are going to walk you through thespecifics of a basic port job. As an example, we'll port astandard cast iron head as used on a 5.0-liter ChevroletSmall-Block V8; however, all basic porting techniquescan be applied to the head or heads on any engine,regardless of its manufacturer, configuration or numberof cylinders.

To illustrate the improvement that comes with basicporting work, at the end of this web page, we'll post flow

test results, both before and after porting.

Materials,Tools andSafetyThe first itemsyou need areour StandardAbrasivesDeluxe PortingKit and ourStandardAbrasives 3-inch

Gasket Removal Kit. These contain all the abrasiveproducts required to perform a basic porting job on apair of cast iron or aluminum cylinder heads.

The components in these kits are designed for mountingin a die grinder having a maximum speed of 18,000-20,000 rpm and a 1/4-in. diameter collet or "chuck." Donot use an 1/8-inch collet grinder of the type used inhobby or arts and crafts work.

An air-powered die grinder is desirable because of itsrelatively low cost and variable speed. An air grinder willrequire a compressed air source. Most compressors



This display shows all the items one needs toport a set of heads the easy, Standard Abrasivesway.

This particular air compressorhas a built-in pressure regulator.The pressure control on thepanel selects the regulatedpressure.The gauge on thepanel reads regulated pressurenot the tank pressure. If you usean air grinder, whatever

compressed air source you useshould have an adjustableregulator.


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The point of this exercise is to get a feel for the diegrinder fitted with different tools. Prior to starting yourpractice, use the wood blocks to support the head in amanner that makes the head deck and intake andexhaust port surfaces easy to reach. Lift up the headand place a block between your work bench and a headbolt boss or other surface of the head that will sit on theblock.

The first die grinderoperation to learn ischanging tools. Virtuallyall die grinders comewith a set of wrenchesused to loosen andtighten the chuck.Typically, one wrenchholds the air grindershaft and the secondwrench turns thechuck's nut.You loosen

the nut, insert the tool, then tighten the nut. In theprocess of your basic porting project, you will changethe tool many times. Always disconnect the air grinderfrom the air source and the electric grinder from thepower source when changing tools.

During your practice work, learn to control the grindersuch that you move it smoothly. Grinding in one placewill result in removal of too much material and unevensurfaces. Also, this is the time to set the speed of thegrinder.You neither want to exceed 20,000 rpm nor doyou want the grinder to chatter. Remember, best speedis 10,000-12,000 rpm. Review the previous discussion

about grinder speed if you need to change it.

If you are working with aluminum heads or intakemanifolds, regardless of the type of abrasive, use amore gentle touch than you would if you were workingcast iron. Because aluminum is softer than iron, itabrades faster. If you use the same grinder pressure youwould with iron, before you know it, you will have shavedoff too much material. Additionally, under mostconditions, the abrasive tool will "load- up" with cakedon aluminum as you work. Spraying the tool frequentlywith a light lubricant, such as WD-40, reduces thisproblem.

Throughout this job, your quality control device will beyour finger. During your practice work, find a reasonablyflat spot on the exterior of the head. Use the 40-grit then80-grit cartridge rolls to smooth a square-inch or so ofthis area. Use the exterior of the head because youwant your finished work to be easily visible. Strive for aneven finish with the 80-grit. Then, take off your glovesand use your finger tips to feel the area you have justprepared. Think carefully about what you are feeling.Hold that thought.

After you feel confident you have had enough practice

are dangerous when proper safety procedures arefollowed; however, misuse of the tools or failure toobserve safety procedures may result in injury.

Porting work throws lots of metal chips around, so thefirst thing you need to protect are your eyes. Theminimum protection is shatterproof eye wear designedfor industrial use. Better is a set of goggles with ashatterproof lens. Best is a face shield made of

shatterproof material.

Next, you need snug-fitting work gloves. We recommendthe Goodyear brand since they allow a good sense oftouch while still offering protection. An alternative is ageneric leather work glove of medium thickness. Avoidthin leather gloves or the very thick units intended forwelding. Do not use rubber gloves.

The last two pieces of safety equipment are optional butsuggested. People sensitive to airborne dust may want arespirator mask such as the type used by paint andbody shops. These inexpensive, white cloth masks areheld to your face with an elastic string.

The noise some air grinders make is quite loud. If theloud power tools are a discomfort, do your port workwearing ear protection. Best are the muffs airportworkers wear around jet engines. Acceptable are a setof ear plugs intended for industrial use.

Goodyear gloves can be found anywhere racers buyparts and supplies. You should be able to find the rest ofthis safety equipment at a hardware store. Dedicatedsafety vendors, such as Lab Safety Supply, are also

good sources.

You need a waist high work bench with about a three-foot by five-foot area of clear space. Consider thelighting of your work area, too. Gauging the quality ofyour porting depends on you being able to easily seethe work. If your garage or other work area is dimly lit,consider investing in some fluorescent shop lights or atleast some temporary, auxiliary lighting.

As this project will probably extend over several days,you will want to clean up the work area from time totime. Know that under certain conditions, aluminum dust

is a fire hazard. Dispose of aluminum particles and dustin a covered container.

If you have never used a die grinder to deburr, port orpolish engine parts, we suggest you obtain a junk headand try a bit of grinding with some of the abrasiveproducts in the Standard Abrasives Porting Kit beforeyou start on the heads from your engine. What you wantfor your practice session is a head that is damaged orotherwise unserviceable. Sources for this are wreckingyards and automotive machine shops. Best bet is to geta head similar to the one on which you are going to doyour basic port work.



Tool changing is the first die grinderskill one learns. Most die grinders usethe type of chuck that is tightened withtwo open-end wrenches.


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grinder, put on your eye protection and gloves, then starremoving the gaskets the easy, Standard Abrasives way.Once the gasket surfaces are down to bare metal,disconnect the grinder and remove the conditioning discset-up.

In most cases, your port work will start with enlargingthe "port entry" area to the size of the openings in theintake manifold gaskets. Later, you will reshape the

ports in the intake manifold to this same size.

To ensure the head portentry and the intake manifoldport end up the same size,you scribe an outline of theintake gasket openings onthe head and the manifold.

Machinist's bluing is usedfor this. Apply it to theintake gasket surface

around the intake ports and allow it to dry. Place thenew intake gasket in its normal position and hold it withmanifold bolts. Scribe theinside perimeter of each intakeport onto the gasket surface ofthe head, then remove thegasket.

Pay close attention to theposition of the gasket on thehead. If it is upside down orbackwards, your scribe markswill be in the wrong locations.That will cause a seriousproblem with your port work.

2. Preparing the Intake Port EntryInstall the large, conical,rotary grinding stone (partno. 263901) from thePorting Kit into the grinder'schuck. Tighten the chuckthen reconnect the air hoseor electric cord. Rememberto put your eye protectionback on if you remove itduring the change.

Now you are ready to do your first porting work. You willenlarge the port openings in the intake gasket surface

on the junk head, lay out the "good" heads you will porton the bench. They need to be completely disassembledbefore any port work is attempted. Consult a factoryservice manual if you are going to take them apartyourself or have an automotive machine shop do it foryou.

After disassembly, if the heads came off an engine thathad been in service a while, they will need to be

cleaned. We suggest you have iron heads hot-tanked. Ifyour heads are aluminum, make sure whatever cleaningmethod you choose is safe for aluminum.

Used heads should be carefully examined for cracks,especially around the exhaust valve seats. Additionally,used heads should be pressure checked to make surethey have no coolant leaks. If leaks or cracks are found,have them repaired before doing any port work.

1. Removing Old Gaskets and Marking theIntake Ports

Even though the heads have been cleaned, the gasketand deck surfaces should be conditioned to remove all

traces of old gaskets, paint, gasket sealer, corrosion anddirt. The use of a putty knife or scrapper for this purposeis not acceptable because neither will clean thosesurfaces completely. If your heads are aluminum, a puttyknife or scraper may even damage those surfaces.

The StandardAbrasives' 3-inchGasket Removal Kitis the proper way tocondition the gasketsurfaces withoutdamaging them. It

contains surfaceconditioning discs foruse on cast iron andaluminum along witha holder pad thatattaches to your diegrinder.

Disconnect the grinder, install the Standard Abrasives'surface conditioning disc holder into the chuck andtighten the nut. The conditioning discs use StandardAbrasives' unique SocAtt locking system, so installation

is as simple as a twist of your wrist. Reconnect the



Machinist's blue, in this case spray-on Dykem, is applied to the areasurrounding the intake port entriesin the head.

The areas inside of thescribe lines are the placeswhere material will beremoved.

The intake manifold gaskets,in this case a set of Fel-ProPerformance Gaskets, are

installed on the head. Intakebolts hold them in place andan outline of the inside of thegasket's intake port is scribedon the head.

The first porting operations areusually done with the rotarystone.

The solution is the Surface Conditioningdiscs in Standard Abrasives GasketRemoval Kit.They abrade the surfacedown to bare metal but do no damage inthe process.

Even after it was hot-tanked, this cylinderhead still has very dirtyintake gasket surfaces.Most used heads willcome out of the hot-tankor cleaning bath thisway. Note the sharp-edged "step" formed bythe corners of the portentry in the head.


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by removing materialinside of the scribemarks you made. Then,you'll blend or "feather"the now larger portopening into theremaining port byremoving progressivelyless material as you

move down into theintake port. In mostcases, you want to grind

from the port entry to about 1-1.5 inches into the port.

From your initial practice on the junk head, you knowthat the stone removes large amounts of material ratherquickly so pay attention to control of the grinder. It isbetter to go over the work with several light-to-moderatepasses rather than doing one heavy pass, remove toomuch and possibly render the head useless.

Certain heads, such as Chevy small-block V8 units,have pushrod holes in close proximity to the port wall,

just downstream of the port entry. Enlarge the port entrytoo much and you will grind into a pushrod hole. Thismay destroy the head or at least cause a very expensiverepair. Adequate work on the practice head will help youavoid that.

To see how far you can enlarge the port, go back to thejunk head and grind one of its port entries until you cutinto the pushrod hole. After that, you will know howmuch you can grind in that area without damaging thehead.

Once you have removed the majority of material with thelarge stone, you may need to switch to the smalldiameter, conical rotary stone (part no. 263061) toprofile the small radii at the corners of each port.

The most important thing to remember about rotarystones is they remove large amounts of material. Theyare not for final surface finishing. There may be basicport projects that do not require removal of largequantities of material. An example might be a productionhead on a high-performance engine. Those heads mayalready have fairly large ports and you will find the

material to be removed inside the scribe marks isminimal. In that case,the rotary stones maybe unnecessary.

Disconnect thegrinder, remove thestone and install theshort cartridge rollmandrel (part no.269111). Cartridgerolls come in avariety of sizes and

shapes. The Kit includes straight rolls in two grits andthree diameters, half-taper rolls in two grits and twodiameters and full-taper rolls in two grits. Different gritsare necessary to get the proper finish. Cartridge rollwork starts with 40-grit then switches to 80-grit. It is notpractical to go from a virgin surface or one that hasbeen worked on with the rotary stone to proper finishwith only the 80-grit. It takes too much time and you'dneed more 80-grit rolls than there are in the Kit.

Large-diameter, straightcartridge rolls are forfinishing relatively flatsurfaces like port walls,floors and roofs. Thesmall straight rolls arefor finishing long,radiused areas, such asthe corners of intakeports, or areas of convexcurves such as the corners of the valve guide bosses orthe short side radii. The half-taper and full-tapercartridge rolls are better used on surfaces with concave

curves, such as the"bowl" areas at the topof the valve pocket orcombustion chambercorners. Additionally,half- and full- taper rollsare better to use whenthe tool approaches thework from a steepangle, such as workingon the valve guide boss

through the valve hole.

With the mandrel in place and tightened, place one ofthe large, straight 40-grit cartridge rolls (part no.263161) on the end of it. Note the little orange spot onone end of the roll. Point the spotted end towards thegrinder, then screw the roll onto the mandrel. Reconnectthe air or power supply.

Begin finishing the flat areasin that first 1-1.5 inches pastthe port entry. Only workdeeper in the port if there

are excessive bumps orcasting flaws. Remember tofeather the smooth area intothe surrounding virgin metalat the end of that 1-1.5-inches down the port entry.

Once you have worked theport entry with 40-grit, switchto the large, straight 80-gritcartridge roll (part no.263163). The 80-grit givesyou the smooth, but not

The Cartridge rolls in the StandardAbrasives Porting Kit come in a widevariety of shapes and sizes.

You start with 40-grit rolls andprogress to 80-grit. In manyintake ports, the small-diameterrolls will be needed to finish theradii at the corners of the por t.Typically, you polish only 1-1.5inches down the port.

The cartridge roll mandrel hasthreads that hold the roll. Each rollhas an orange spot which is pointedat the grinder. All you do is push thecartridge roll on the mandrel, then

screw it tight.

Cartridge rolls also come in two grits,80 (left) and 40 (right).

When using the stone, remember that

1) it removes material quickly and 2)smooth, controlled movement of thegrinder is necessary.


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polished, surfacethat is correct forintake ports.Once you finishthe 80-grit step,stop, remove yourgloves and feelthe surface.When your tactile

"QC checker"senses the rightfinish on all theport walls, you'redone.

3. Short Side Radius and Bowl WorkThe point where the intake port floor curves down to thevalve seat is known as the "short-side radius." From anairflow standpoint, this area is the most critical in anyport. Smooth that spot and there usually is a significantincrease in flow through the port.

With most production heads, the short-side radius willbe sharp-edged and rough.The goal is to soften thosesharp edges and smooth the roughness. Depending onthe location of the radius and how you are approachingit, you may keep the short mandrel in the grinder or you

may need to switch tothe long mandrel(part no. 269149).Start with the smalldiameter, 40-gritstraight cartridge rolls(part no. 263021)and, depending onthe location of the

radius and the toolangles necessary toapproach it, you mayalso need to usesmall, 40-grit, half-tapered (part no.263351); large, 40-grit half-tapered (part no. 263751) or40-grit, full-tapered (part no. 263301) cartridge rolls.Again, you start with 40-grit and switch to 80-grit.

Short side radius workis the first time you willbring abrasives near

the valve seat and thatis the one place youwant to avoid hittingwith any abrasive orrotating part of thegrinder. Even thoughyou will have a valve

job done to your headsonce the port work isfinished, it doesn't takemuch of a hit on thevalve seat to render itunusable even after avalve job.

The next step is to do the roofs of the valve pockets andthe valve guide boss. Called "bowl work", this willrequire a mix of the different small-diameter, taperedand straight cartridge rolls. Remember to start with 40-grit and finish with 80.

The valve throat is the smallest diameter in the valvepocket just above the valve seat. A general rule is thatthe valve throat should be about 85% of the valvediameter. If you measure the throat to be smaller than

that, using a combination of the rotary stone andcartridge rolls, open that diameter up to the 85% figure.If you attempt to open up the valve throat, first practicethe technique on your junk head.

4. The Exhaust PortGoals for the exhaust port are similar to those weachieved with the intakes: To reduce restriction to gasflow, but your methods are going to be a bit different.

Exhaust gases carry combustion by-products, of whichcarbon is a component. Over time, carbon deposits buildup on the exhaust port walls and that can impede

In some cases, depending on portlength and the position of the valveguide, it may be necessary to switchto the long cartridge roll mandrel andwork on the guide through the intakeport entry or the exhaust port exit. A

full-taper cartridge roll works best forthat.

(A) In this production intakeport, air starts into the portflowing smoothly. When itencounters the casting bumpon the floor of the por t, smoothflow breaks into tumbling andturbulence.This causes

restriction to the overall airflowin the port.

(B) The turbulence in theairflow becomes more severeas air passes the sharp edges of the short side radius in this drawing.Smoothing the radius and removing casting bumps and flaws reducesturbulence and increases flow.

With this cutaway,we polished thewhole port to betterillustrate the rough-to-touch finish.Note the smoothedvalve guides andshort side radius.

Bowl work is the second part of the basicporting. Here a half-tapered cartridge rollis used to smooth the valve guide. Whilethis picture shows work on an exhaustport, the valve guide work is the same beit in an intake or an exhaust.

Best way to gauge the finish on the por t wallsis with your finger. For intakes, you want thesurface slightly rough to the touch but withoutwaves, gouges or low spots.

Here is a finished intake portentry. Note the slightly roughfinish. At right is a partiallyfinished port.The floor isuntouched and a large castingmark is evident. Also, note thedifference in port heights.Thisis because the left port hasbeen matched to the gasketwhereas the matching of theright port has not beencompleted.


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exhaust flow. To make theport walls more resistantto carbon build-up, in thefinal step you will give theexhaust port as smooth atexture as possible, a"near-mirror" finish, if youwill.

The initial exhaust portwork is very much likewhat you did to theintakes. The major part of

the finishing and polishing will often be done with small-diameter, straight and tapered cartridge rolls. Do theport exits, bowls and valve guide work just like you didon the intakes.

Once you are donewith the cartridge rolls,remove their mandreland install theStandard AbrasivesCombination Mandrel(part no. 269201) andscrew the 120-grit flapwheel (part no.262618) onto it. Theflap wheel is used totake the finish one step past what you put on theintakes. Use the flap wheel on every part of the exhaustport you can reach.

Once your flap wheel

work is done, remove itand install one of thesmall, hex-socketed setscrews into theCombination Mandrel.Tighten it, then screw oneof the maroon-colored, 3-ply, 1 1/2- inch, medium-grade, Cross Buffs (partno. 265054) onto the setscrew. Standard AbrasivesCross- Buffs are the mostunique product in the

Deluxe Porting Kit.Theywere designed exclusivelyfor automotive use. Of all

abrasives in the Porting Kit, Cross Buffs are mostsensitive to grinderspeed and shouldbe run at 10,000rpm for best results.Also, Cross Buffsneed to be usedwith a light lubricant,such as WD-40.

Begin working the exhaust port with the medium CrossBuff. Once you have hit as much of the port as you canwith the medium, make a final pass with the red, 3-ply, 1

1/2-in. very-fine-grade, Cross Buff (part no. 265056).When you are done, the exhaust port walls will have thatnear-mirror finish that will resist carbon deposits.

In most cases, you never port match the exhausts. Manystock exhaust manifolds and virtually all tube headerswill have larger port sizes than do the heads. You wantthat "step" from the port to the larger header tube orexhaust manifold because, as pressure pulses flow backand forth in the exhaust system, it acts as a "reversiondam" by resisting back flow of exhaust gases into theport. If you end up with the rare situation where thestock exhaust manifold has ports smaller than those in

the head, you will need to port match. Use the sametechnique used to match the intakes.

5. Polishing the ChambersYou want to put the near-mirror finish on the combustionchamber walls for two reasons: 1) As a deterrent tocarbon build-up; and 2) to eliminate any sharp edgesthat can cause pre-ignition. The first thing to do is cleanup the stems of your junk valves (Cross Buff or one ofthe surface conditioning discs will work well) then installthe valves into the chamber you will be working on.Theywill protect those all-important valve seats as you polish

You want to flap wheel allaccessible areas of the exhaustport

When flap wheel work is done, anAllen stud goes in its place.

This is a finished exhaustport. Note the smoothedvalve guide and short sideradius. Also, note the finishis significantly different fromwhat we saw on the intakecutaway.

Initially, the exhaust port exits areworked just like the intake port

entries; however, they are finished bypolishing the full port and using finerthan 80-grit abrasives.

After cartridge roll work is complete,you switch to the Combination Mandreland attach the flap wheel.

The Cross Buffs in the StandardAbrasives Porting Kit come in two grits;medium and fine.

Use the Cross Buffs justlike you did the flap wheel;on all areas of the port youcan reach. A light oil mustbe used with Cross Buffs.

Cross Buffs are screwed onto the Allenstud in the Combination Mandrel.


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the surrounding chambersurfaces.

Spray the head deck withmachinist's bluing, theninstall one of the headgaskets you will use toassemble the engine.Scribe the outline of

each chamber hole in thegasket on the deck.

Most important to rememberduring chamber work is thatyou want to remove as littlematerial as possible. Everybit of metal you polish awayincreases chamberdisplacement a tiny bit andreduces your compressionratio a correspondingamount. For that reason,you must not use the rotary stone for chamber polishingunless you need to unshroud the exhaust valves.

Nevertheless, you cannot polish the chambers with justCross Buffs.You must use the cartridge rolls first. Next,smooth the sharp edges where the chamber meets thedeck, but do not grind past the line scribed around thechamber.You may need the larger cartridge rolls for thechamber's flat surfaces.

Exhaust valve"shrouding" occurswhen, at high valvelifts, exhaust flow isimpeded by thecloseness of thechamber walls to theedge of the openexhaust valve.Shrouding is commonwith pre-1971Chevrolet small- and

big-block V8 and early289/302 Ford Windsorheads. At .300-.400valve lift, there shouldbe 3/16-in. or morebetween the edge ofthe valve and the adjacent chamber walls. If you do lack3/16-in. clearance and there is material between theedge of the chamber wall and the gasket openingscribed on the head; remove material along thechamber wall such that exhaust valve shrouding isreduced. Only remove material inside the scribe line andonly enough to achieve the clearance.

Once your chamber workwith cartridge rolls iscomplete, go over allsurfaces with the 120-gritflap wheel. Finally, do thechamber with, first, themedium Cross Buff andthen, the very-fine CrossBuff.

As a final-touch that willenhance engine cooling, take a small-diameter, 40-grit,

straight cartridge roll or thesmall rotary stone andremove any casting flashthat is in the coolantopenings in the head decks.You will be surprised at howmuch of that you find.

6. Port Matching the Intake Manifold

If necessary, clean thegasket surface of the intakemanifold with the surface

conditioning discs in the Standard Abrasives GasketRemoval Kit and apply the machinist's blue.

Get out the intake gaskets you used to scribe the intakeside of the heads and install them onto the intakemanifold. Verify that the correct sides face the manifold.Scribe an outline of the inside of the intake portopenings on the manifold.

Port-match the intake manifold using the cartridge rolls.If there is a lot of material inside the scribe marks toremove, use the rotary stones. If you are doing your

This particular head did not have anexhaust valve shrouding problem;however, heads with small chambers

and big valves may have the problem.The easiest way to check for it is tohold the valve open about 3/8-inchand use a ruler to measure thedistance between the valve edge andthe chamber wall.

This is what a finished chambershould look like.

The Fel-Pro intake gasket isused again to mark themanifold.You want the top of thegasket to face the manifoldwhereas you had the bottom ofthe gasket facing the head.

Cross Buffs are used to finish the

combustion chamber.

Before doing the chambers, installa set of valves to protect the valveseats.

Most heads will have a lot ofcasting flash in the watercrossovers. Use a smallcartridge roll to remove thatflash.

The spray Dykem is again used onthe intake manifold.


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basic port project on anengine with an aluminummanifold, remember to usea more gentle touch thanyou would if you wereworking cast iron.

So...does it work?DIYs are a tough crowd. Skeptics abound, so weneeded a flow test of our heads before and after basicporting. We retained Valley Head Service in Northridge,California to run those tests. After our basic portingproject was complete, intake port flow improved 15.3%at low valve lifts, a significant change. Averageimprovement, from .050 to .500-in. valve lift, was 6.3%.In the exhaust ports, gas flow at medium valve liftsimproved a whopping 17%. Average improvement ofexhaust flow was 7.5%. The exhaust ports showed thegreatest change, which is typical of a production Chevy

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The port matching of the intakeis accomplished like that of theintake port entries in the head.If a lot of material needs to beremoved, start with the rotarystone, otherwise, use a 40-gritcartridge roll. Remember touse less pressure on thegrinder because aluminumabrades quicker than iron.

The port exits in the intakemanifold should feel just like theport entries in the head; slightlyrough to the touch.

head. For an engine of 300 horsepower before porting,these improvements in flow would make an approximatepower increase of 19hp.

Note that we did not skew the results by flowing thehead after a multi-angle valve job. Our tests were donewith stock valve face and seat angles. Airflow of thehead after a good, high-performance valve job wouldimprove even more.

Final RemarksYour basic porting project will go more smoothly if youorganize your work. Dividing the job into sections willenhance your consistency and shorten time on the jobby reducing the amount of tool changes.

Start on the intake port entries first. Hit them all with therotary stone, then do the cartridge roll work. Next, dothe intake bowl work. The third section of the job gets allthe exhaust ports and bowls. Finish the heads by doingthe chambers. Close out the whole job with the intakemanifold port matching. Hold-off on having a valve jobdone on the heads until all abrasive operations arecomplete. A multi-angle valve job is best on headsdestined for any high-performance application becauseit offers additional improvement in low-valve-lift air flow.

You also can contact us using email or you can call usat 800-383-6001 or you can write us at StandardAbrasives Motorsports Division, 4201 Guardian St., SimiValley CA 93063.

Copyright 2006 Standard Abrasives - All rights reserved - Anyunauthorized copying or distribution forbidden by law.

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Head Porting