Harley-Davidson® spells hundreds of dollars for your shop

By Joe Mondello


This article covers the proper way to port and polish Evo and Twin Cam 1998 to present cylinder heads with or without valve guides in place. My way to do a great valve job and maintain the 89% throat dimension for intake and exhaust ports will achieve the highest horsepower and torque numbers in the country. I will briefly touch on cams, but the most important component of these Harleys is the big bore kit with real, usable compression ratios on today’s gasolines. We will discuss how to bore and hone the barrels to keep them straight and round.

Cryogenically freezing the heads, pistons, rings, and barrels; then applying high heat and lubricity coatings make for a cooler running bike with no detonation — even on the 10:1 and 11:1 for street use. When using the higher ratio pistons a compression release valve needs to be installed in the cylinder heads.

On these hot summer days and nights, grab a beer, sit back and read all about it! The cost is really not much for porting supplies; you might need to add a few more carbide cutters, flapper paper, some porting valve guide height gauges, and my signature series Mondello 2010 porting lube to your stock, but it’s well worth it.

The proper way to bore and hone with correct torque plates will require a small investment to do a good job. Coatings and freezing you will have to farm out. If you now use Neway 30, 45, and 60 degree angle cutters for performance use this will have to change. Use the multiple angle seat cutters to obtain good flow numbers and throttle response; get away from that old school stuff. The old cutters can be used on other jobs; they are better than stones but once you use the 3D system and multi-angle cutters you will see what I mean. My signature series cutter blades, distributed by Goodson, are absolutely the best in the industry. We prove this daily in all applications; our numbers out-shine all those you find in other magazine articles.

It’s not as easy as you might think. You have to achieve good port designs and shape, keep the 89% throat dimensions, create good port and combustion chamber finishes plus do a multi-angle valve job, make the proper cam choice, and most of all have a great piston ring seal in your cylinders.

Now, after all this is said and done, you must choose the best ignition system, tuner and exhaust pipe. Then, after it’s all buttoned up, you need to find an expert individual to put your bike on a chassis dyno and tune it with performance upgrades!

I have built hundreds of sets of Harley heads, together with big bore kits and good cam choices, they have shipped all over the world and guess what? There is a difference of about 20-25 horsepower and the same amount of torque from the same combinations going to different builders and tuners! All my parts, heads, compression ratios, and cams are equal but the difference is between the individuals who assemble them. This really blows me away so here are some tips to keep the numbers high.

When porting your heads with the guides in; drive the guide down from the valve seat side about 1/2 inch. This will allow you to have more room to port and shape around the back side of the valve guide boss. Partially shape the gussets on each side of the guide boss towards the port opening intake and exhaust. You will finish shaping the front of the valve guide bosses from the valve bowl side. Do not remove material on the back side of the intake or exhaust valve bowl area behind the valve guide bosses.

When porting the valve bowls and shaping the guide bosses, an 18-20 tooth regular cut 1/2” diameter egg/oval carbide cutter is the best to use unless you are a good porter with much experience. If you are very confident, use an 8 tooth fast mill cutter like I do to rough in your ports much quicker. I like to shape the intake port and port mouth, shaping the “D” port with an 18-20 tooth regular cut 1/2” flame carbide cutter. If any ridges, high or low spots appear where the port blends into the valve bowl and guide boss area, use the 1/2” egg/oval to blend.

Always try to keep your cutters as flat to the surface you are porting as possible. This applies to all carbide cutters, cartridge rolls, flapper paper and cross buff pads, too.

Always use a good porting lube like my 2010 on all items listed above. A very light mist of the lube is all that is needed.

When porting your heads with the valve guide in, totally finish all porting operations before you drive the valve guides back into their stock height.

While doing the valve bowl porting be sure you do not exceed the 89% throat dimension. Usually all Evo, Twin Cam, and V-Rod heads are smaller than 89% so be sure you do not open up the throat dimension with an 86° or 90° straight blade cutter while doing your finish valve job. We hand grind and finish our throat dimensions to 89% of the valve size with a 24 tooth 1/2 regular or double cut round nose tree or egg/oval carbide cutter. Again, be sure to use a good porting lube like my 2010.

When porting heads without the valve guides in you should use our porting plugs; inserted from the spring seat side of the head into the valve guide hole (HDP4 set of 4 – .500, .600, .700, .800); to determine the height of the roof of the intake and exhaust ports. You should shorten the valve guide boss at a slight angle towards the back wall of the intake or exhaust valve bowl; grind the boss down until you can touch the front edge of the plug making sure you have the plug tightly pushed manually up against the spring seat. We use the plugs to maintain a correct height in the runner. I like to use .600 on the intake and .700 for the exhaust. I use an egg carbide to shorten the valve guide bosses and re-form the gussets next to them. Shape a small fin going out towards the intake port mouth but do not make it sharp; leave it gently rounded. In the exhaust side, after you shorten the guide boss and for the gusset, use a rounded shape towards the exhaust mouth opening. Egg and flame shaped carbides work best for this.

On early Evo and Twin cam heads (1998-2004) make a “D” shaped exhaust port. They make more power and torque. We have a layout flange available which you can use to grind the perfect shaped “D” port (item #DP-TC). Put the flange in the exhaust port and rotate it until the flat portion of the “D” is at the same angle as the exhaust valve seat on the floor of the exhaust port.

In the 1998-2004, there is a large bump on the exhaust port wall. Totally remove it and straighten that wall back into the valve bowl area. I supply the intake layout rings for most Evo and Twin cam heads.

Next, you must re-shape the short side radius. I have designed a special carbide cutter just for this porting procedure. It is a reverse teardrop shaped like an ice cream cone (RT series) which comes in 7/16 and 1/2 diameter recommended in 22 tooth regular cut for this project. You don’t want an aggressive cutter in this area. If you are going to flow test just roll the short side radius from the bottom of the seat into the floor of the port with a smooth, rounded shape. If you need more top end air flow then lay back the short side radius making it flatter to the floor. Be very careful here because you can ruin a good set of heads by removing too much material from the short side radius.

As you complete these rough-in procedures remember the smoother the porting job the easier the polishing is! After I rough-in my ports using the finer 18-20 tooth regular cut carbide with 2010 porting lube I start my polishing operation with a 1/2 x 1-1/2 x 1/8 60 grit straight full round cartridge roll using porting lube to clean up and blend any imperfections left from the carbiding. Sometimes you may have to use a 1/4 or 3/8 diameter roll to get behind the valve guide bosses.

Once you are through smoothing with the roll, use the flapper paper stick. I finish the intake ports at 80 grit for a carburetor and go to 120 grit for fuel injection. When you roll up the flapper paper, use a 6 inch strip with the end flush with the slot and roll it clockwise; away from you holding it tight while turning it into an ice cream cone shape spiral. Adjust the grinder air speed so you can nearly stop the flapper stick with your fingers. If the paper is bouncing, it is not wound round or tight enough; if it is shredding or flying apart the grinder speed is too high.

If I’m going to use high temp non stick coating on the exhaust ports I finish them with 80 grit flapper paper. Otherwise, I go to a high finish using in 80,120,150,180 grit then use medium and ultra fine crossbuffs. Again, all abrasives should be used with porting lube.

Your next step is to install new valve guides. I recommend AV&V bronze. Always measure your guide holes after the guides have been removed. Do not order in .001 over assuming the stock guides were indeed .5625. I have seen some Harley heads from the factory that had smaller than stock guides in. Always mic the guide holes.

When installing the guides, heat the heads from the valve cover side to between 150-175° then freeze the guides in home freezer two hours or use Minnesota Fast Freeze from Goodson.

Use an AV&V carbide reamer or diamond hone for proper valve guide clearance of .0012 – .0014 intake and exhaust with chromed stem stainless steel valves. When using high speed or nickel plated reamers, material flow back will occur leaving an inaccurate sized hole. A Sunnen “Hone-All” valve guide tool will also work but I recommend breaking the edge at both ends of the stone into a taper.

Now you are ready to finish honing your valve guides. Start on the valve job. I like to use a 1.900 intake valve for 88 CI engines and 1.940 on 95-107 CI engines. The 1.575 stock exhaust valve makes the best power and torque with 1.900 or 1.940. Many think if you install a 1.940 intake valve you must replace the seat — no, you don’t. On this performance set of heads do not use the Neway valve system because the angles are not right, nor are the widths of the cuts. I recommend the use of my Harley-Davidson cutters, available through us or Goodson, using a 3-D system or DMC, Serdi, Sunnen, Kwik-Way, etc. Doing the valve job correctly will give you 15-20 cfm more flow on intake and exhaust plus higher velocity than any others.

Use IFT4539B-HP intake seat cutter, then use the IFT1556HD to top cut the ridge in the chamber that is left by IFT4539B-HP cutter. Intake seat angles are 45° primary cut, 39° top cut, 60° bottom cut. Below 45° this cut width should be .080 – .100 wide, top chamber cut blending in 39° top cut use IFT1556HD radius cutter. Just use the edge of radius to blend into chamber floor. Blend in the 89° below 60° bottom cut to finish off. Exhaust seat angles 45° primary cut, 39° top cut, bottom cut full radius. This will have a ridge at the bottom of the radius and will have to be blended to your 89%. Use the same radius top cutters as the intake to blend into the chamber floor.

Remember, when doing the valve job you must know what the camshaft overlap is so the valves won’t hit each other. For 98% of our head jobs we use a 2.030 stem height for intake and exhaust. This is the valve tip height measure from the spring seat to the top of the valve. Always port your heads and do the valve jobs in pairs as it is easier to match guide boss uniformity, D port shapes, and the short side radii to each other.

I do not want you to port the combustion chambers; only blend and polish them. If the chambers are black power coated, use a 60 grit cartridge roll or bead blast to remove coating. After the valve job is finished, make some chamber valves to cover the 45° seat angle. Use an 80 grit cartridge roll to blend the top cut angles into the chamber floor and sides. After blending, use 120 grit flapper paper, then 150, and 180 grit.

After flapper sticking, use a medium, then a fine cross buff to final finish. Do not enlarge the chamber, just clean it up.

Always CC the chambers as most aftermarket pistons are made for 84 CC chamber volumes. If you are going to coat the chambers use just an 80 grit flapper for your final finish.

Let’s talk a bit about cams and compression. Most pick a cam that is too large for the CI displacement, compression, and total weight of the bike and passengers. I like cams for unported heads to be .500 – .540 lift; .220° – .240° duration at .053 between 106 – 112 lobe center line 88 – 95 inches up to 10:1 compression. With ported heads of 9.5:1 – 11:1 compression I recommend gear drive and chain drive conversions 226° – 260° at .053, .510 to .600 lift; 100 – 106 center lines.

My choice of cams is Wood Performance and Andrews Products. Compression ratios with 10+ to 11.5:1 compression release valves should be installed. Cermet combustion chamber and piston top coatings with molyedium disulfate coated piston skirts plus coating the intake and exhaust valves and exhaust ports is a great power and torque enhancement; especially with today’s junk gasolines to eliminate pinging and detonation.

I left the boring and honing for last because if you could see how a lot of shops do their boring and honing…well, you wouldn’t believe what they do to your barrels! I have spoken to many of these guys and they really think they are state of the art mechanics and machinists — HA! Many (even the Harley factory), now and years ago, use steel torque plates to final hone the barrels then bolt an aluminum head to it. Let me tell you — steel and aluminum don’t have the same clamping force so the barrel distorts and now the ring seal is no longer good. Even aftermarket torque plate honing kits come with steel torque plates top and bottom and they supply grade 6-8 bolts for you to bolt everything together.

Many of you are pretty sharp, I know; I’ve spoken with you, so you know where I’m going with this! You cannot bore barrels on a lathe and keep the concentricity true because you only have support on one end. You cannot use the above described torque plates and bolts for a good honing job — clamp it in a big vise, grab a Sunnen, Lisle or Ammco hand hone with a medium grit then a fine stone using motor oil thinned with cleaning solvent or Kerocene and expect this hole to be round or straight!! Come on, you can’t control the stroke and cross hatch or the heat generated from this process and the finish for a good quality piston and ring combination to seat properly.

At Mondello Tech Center, we make our own torque plates from basically the same aluminum density thickness for both top and bottom plates; use the same bolts and fasteners, and the same head gasket thickness and material content as at final assembly. We freeze all barrels before boring and honing. Four barrels are installed in our precision torque plates using the correct studs and head gaskets torqued to factory specs and put in our 70° constant temp final assembly room a minimum of six hours before we put them in the computerized V-30 Sunnen RMC for boring and correcting concentricity.

After they are bored to within .005 of finished bore size and the same fixture is bolted into our Sunnen SV-10 computerized honing machine, we rough hone with diamonds to within .0025 and finish hone with stones for final ring seal.

The final procedure is using 220 grit to size 3 strokes of 280 and 3 strokes of 400 light to medium pressure. The resulting barrels are very straight and round and will run many thousands of miles for you with good ring seal as we use plasma molyductile ring sets. We use MLS head gaskets for all the big bore kits as they are the best!

I hope this has helped you find a new niche in this modern world of hard times and this has bettered your ability to make more power and torque to make more money and build your base of satisfied customers. My custom torque plates are available, just phone me with your custom order.


Joe Mondello has been involved in quality head porting and R&D at a time when Ed Iskenderian, and a few others started a high performance industry. Joe has been so successful that his tech manual was given a GM part number. Joe is an innovator and educator of the highest order. When he could have sat on his laurels, Joe chose instead to start a Tech Center in Crossville, Tennessee holding classes for any who desire to learn air flow secrets that took Joe a lifetime to find out.

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