01. A Branch-O’Keefe reworked Twin Cam head with an 83cc combustion chamber. The smaller volume as well as the shape gives added low-end torque and more complete combustion.
02. Basic, stock 85cc combustion chamber with limited breathing capacity.
03. A view from outside the head of the stock, restrictive exhaust port; the valve guide is gold colored here.
04. The exhaust port viewed from inside the head after valve removal. Notice the rough and corroded surface of the inside of the port. The large circular valve seat also shows signs of corrosion. None of this is good for maximum airflow or valve sealing.
05. A stock exhaust (left) and intake valve from an early Twin Cam. The Factory used the beefier 5⁄16-inch inch valve stems. H-D cost cutting led to cheaper, less durable valves along with poor-quality, oil-collecting valve collars.
06. Stock set of double wound springs, with heavy steel keepers on top. The added weight adds to power loss through the valvetrain due to the effect of inertia on the spring and valve. The purpose of the coil springs is to return the valve to its closed and seated position quickly after it’s opened by the cam and rocker arm.
07. Combustion chamber and ports early in the Branch-O’Keefe porting process. The larger port on the right is the intake port.
08. An example of a polished intake, with a microscopic, fish-hook finish for maximum airflow velocity and thorough atomization of fuel mixture. Every aspect of head porting, such as where remove or add material, or how smooth is vitally important. Just polishing a port to a mirror finish will not yield great results.
09.** Black nitride intake valve held above the intake port and valve seat—its eventual mate.
10. DYKEM Blue was spread on the valve seat to visualize the results of Branch-O’Keefe hand lapping (grinding) procedure. Hand lapping cleans up slight irregularities in the seat surface for a nice fit between the valve and its seat.
11. Nearly finished. Both ports have been polished while the intake valve set is awaiting hand lapping before reassembly.
12. A view of intake port from outside the head. That’s a huge difference compared to the rough stock intake ports.
13. Fresh valve guides offer precision fitment with the new valves.
14. Fresh set of 5⁄16-inch stem diameter black nitride valves in front of a different set of stock valves.
15. The smaller and lighter titanium collar (left) reduces weight for better valve control; the larger collar on the right is the OEM steel unit.
16. On top of the keeper and spring is a precision-machined titanium keeper on double wound springs for lighter weight and faster ramp-up of rpm.
17. Accounting for tolerances the new valve setup will safely allow up to 0.685 lift cams. We’ll be running a Feuling 0.630 lift, gear drive cam set.
18. This is the beautiful end product of the Branch-O’Keefe head work. But, that’s just the beginning. Come back and see just how well the rebuilt Twin Cam engine performs.
The deadline is tomorrow!” the editor grumbled over the phone and hung up.
I turned to my associate, the performance editor of Bikernet.com, Ray C. Wheeler, and pointed at his computer. We dropped a gear into the scramble mode and went to work. Fortunately, we have been working with Bennett’s Performance in Signal Hill, California, on a Twin Cam engine build. Even more fortuitous, Branch-O’Keefe shares the same building. John O’Keefe now owns and runs the business and worked alongside Jerry Branch—the legendary horsepower guru and the master of cylinder head airflow, velocity, and volume, for several decades. Jerry was a consultant to the official Harley-Davidson XR race teams among others and involved in the development of the Evolution motor.
Let me back up before the deadline bell rings; it’s not uncommon to receive “reminders” from the editor at 2, 3, 4 a.m. This morning he showed up at the headquarters at 5:45 riding around the gated property for an hour before I got out of bed and met him outside. An exchange of pics was made during the predawn run, and just like that, only a melted-rubber-scented dusty cloud remained in his place.
Ray and I are planning to attend the Bub Motorcycle Speed Trials in Bonneville this coming September with two motorcycles. Ray rode his touring-equipped 124ci fire-breathing ’04 Dyna Glide for 50,000 miles, then rode from San Jose, California, to Bonneville in 2009 and set two records with saddlebags on his bike. Then he got serious and added an Aerocharger turbo charger and rode another 30,000 miles before returning to Hardtails, back in San Jose, for a tune-up.
The Bikernet.com 5-Ball Racing Team convinced Ray to pull the 124-inch monster and put it in a Bonneville-dedicated chassis for 2012. So what was he going to do with his touring Dyna? He replaced his highly modified stock cases with S&S; racing cases. Randy at Hyperformance, in Pleasant Hill, Iowa, repaired the Harley-Davidson cases and sent them back to our headquarters. We went to work with Eric Bennett to build him a calm, long-distance, Dyna hot rod touring motorcycle.
We ordered a brand-new RevTech big bore kit that would take the stock 88-incher to 97 inches. We grabbed a Screamin’ Eagle cam plate with hydraulic tensioners for the longest lasting durability and less friction loss. Then we started to search for a lower end and found two reputable Twin Cam lower end rebuilders, one being Dark Horse Crankworks, in Osman, Wisconsin, who swapped the raceless stock connecting rods for I-beam rods with races for much improved heat dissipation and longevity. Plus they replaced and TIG-welded the crankpin into place to remove the chances of flex and slippage, along with balancing the engine to Dark Horse’s secret balance factor for this engine configuration, for smooth running, less vibration, and reliability.
Ray, our hot rod nut, slipped in a nefarious phone call to John, the master builder at Dark Horse, and tried to jack the stroke order from 4 inches for an 88-incher (97 inches with the CCI kit) to 43⁄8 for a 96ci configuration (or 106 with the same RevTech big bore kit). We’re not exactly sure whether he succeeded or not—hang on. The Harley cam drive system also comes with a more efficient oil pump with increased oil volume and flow characteristics, which lends to the overall durability of any Twin Cam configuration.
This engine, designed for long distance, reliable touring was coming together with the absolute best-of-the-best components. Eric volunteered a set of worn stock heads to be rebuilt next door at the nirvana of flow, Branch-O’Keefe command center. The pristine machine shop is lined with heads destined for locations all over the country, Europe, and Japan. John keeps an inventory of more than 100 sets of heads and offers a trade-out for pre-rebuilt heads, for faster turn-around, or he will perform his magic on your set of heads and have them back in the mail within two weeks.
Jerry Branch opened his shop in 1969 and was recently inducted into the Trail Blazers hall of fame. He’s improved the breathing side of champion race team engines ever since. One of his early employees was the young John O’Keefe, who joined the team in 1975, and is still marveled by the energetic 88-year old Jerry Branch. Jerry is currently working with Dan Gurney to build faster cars. John took over the business seven years ago and has kept the high-flow fires burning.
Branch-O’Keefe heads are much more than tried-and-true porting or even welding up and enlarging valve pockets for large valves, reshaping combustion chambers, or shaving heads for added compression. They replace every head-related component with endurance-tested, state-of-the-art titanium valve collars. In the case of late-model Twin Cams, they replace the leaky, spindly, stock valves with stronger 5/16-inch stainless steel valves.
Twin Cam heads from Branch flow about 30 percent better than stock heads across the valve opening range. Actually, stock heads flatten out in one position and don’t flow any additional capacity throughout the remaining valve opening sequence. In that area, Branch heads make big broad-rpm power all the way to redline.
They reshaped the heads through years of trial and error to allow for larger, better flowing valves in the optimum position for complete combustion, since the stock head/valve combination didn’t burn all the fuel, impeding efficiency in the factory engines. The area around the valves became smaller, but they were able to speed up the velocity of the air passing through the ports. In the smaller areas of the head, they were able to add more space around the valve.
John squeezed in a 1.94-inch intake into the combustion chamber, compared to the 1.85-inch stock valve. They were able to design in a larger valve with more functioning space around it. The crest in each port allows for more valve guide support but still enhances the port flow.
John replaced the stock cast iron valve guides with bronze magnesium components. “I like these work-hardened valves and guides, because I can run a much tighter valve stem-to-guide tolerance,” John said. The tighter tolerance affords heat dissipation from the valve through the guide. The enhanced grain structure in the guides acts as a heat sync pulling blistering temps off the valves. All these elements make for a longer-lasting valve train. These amazing aerodynamic guides come with Viton seals built into the structure of the guides. They also run a thicker, more robust exhaust guide for additional heat dissipation.
For Evo heads, the Branch team installs one-piece stainless valves with chromed stems and stellite tops where the valve meets the rocker for additional hardened strength. For Twin Cams and baggers, John recommends black nitride valves with a Teflon coating.
“I use the stainless valves in Evos because the guys don’t lug them,” John said. Branch-O’Keefe valve seats are nickel chromium and capable of running valves up to 2 inches in diameter. The biggest valve you can put on a stock seat is 1.90. The Branch-O’Keefe seats are machined with an interference fit of 0.007-inch so they will never rattle in the heads or ever fall out. Factory seats are only 0.0025-0.003 larger than the hole in the head. He heats the heads to 300 degrees and freezes the seats before assembly. The nickel chromium seat material will take any unleaded fuel and won’t pit.
Each valve seat is cut at 45-60-30 degrees, three angles. With porting, it is the equivalent to a 5-6-angle valve job. Each valve is ground to 45 degrees, and John uses a special carbide-honing bit to ream the guides. It is designed with a reverse spiral so it runs clockwise and it is set to slip fully into the guide before it begins cutting, for an absolute straight ream. Each bit costs more than $200.
John and the Branch team hand-lap each head. “We can modify heads for any performance application,” John said. “It is no longer a one-size-fits-all world.”
The master in the clean room is Paul, a former Honda race tuner. “He’s great at tech support,” John said, and I could tell Paul wanted to talk to the milling machine more than me. “We like to find out what a guy rides, and how he rides,” Paul said. “It helps to find out what they have in their engine, what kind of intake, and carb.” Sometimes, the intakes are polished and Paul can make carb configuration and tuning recommendations. Even Branch-O’Keefe valve springs are top of the line. “We have a five-year track record of no failures or pressure drop,” John said. “Some springs drop 20-30 pounds of pressure in a race bike after just 50 dyno pulls.” The springs are shotpeened, stress-relieved, and then tested at 180 pounds on the seat. The springs are capable of 0.675 cam lift. John uses only chromoly collars and retainers.
If the esteemed editor will afford us the opportunity, we may bring you another tech on the completion on this motor with Crane roller rockers, manufactured by S&S;, Feuling cams, lifters, easy-to-adjust pushrods, and a brand-new Yankee Engineuity EFI throttle body that is sure to rock the fuel injected world. Of course I want to share that big news with the Baggers’ audience. Besides, I still owe you one after you bailed me out following that, um, “misunderstanding” with the South American Federales. –Ed. B
Popular Branch- O’Keefe Head Configurations:
#4 Heads for Twin Cams and Evos
This performance head is designed to fit a variety of engine configurations and riding styles. #4 heads work applications of varying displacements with compression ratios of 9.6:1 for the Twin Cam and 8.9:1 for the Evo. This results in a head that performs much higher than its stock counterpart.
PT Heads for Twin Cams
The PT cylinder head is specifically designed for touring riders with 88-95ci Twin Cam engines. This design provides low-end torque that is often required for heavily loaded, long-distance motorcycles. Compression ratio is approximately 9.5:1 when used with Branch-O’Keefe flat top pistons. The result is power where it’s most needed: in the 2,000-4,000-rpm range.
|Bennett’s Performance||Dark Horse Crankworks||Screamin’ Eagle|
|(562) 498-1819||(920) 726-4990||See your local H-D dealer|
|(562) 597-2850||(866) 966-9767||(515) 266-6381|
|Custom Chrome||Hardtailz||Yankee Engineuity|
|(800) 729-3332||(877) 330-1377||(800) 423-2621|