This thread is just to give people a little more background on the head porting process at HAMMER PERFORMANCE
. This is a process that has been under continual development and refinement since 2003 when I bought my first CNC machine.
HAMMER Dan (Dan Norlin) now owns all the head porting equipment, fixtures, CNC machine, CNC programs, and flow bench, and he's the expert on head porting. So who is Dan Norlin?
If you happen to have a Screamin Beagle catalog from 2004, you'll find his ugly mug in it, for winning the AHDRA High Stakes Shootout in 2003. He's smiling because that was a $12,000 payday. I'd smile too! He's actually won the shootout twice and been runner-up twice. So to say HAMMER Dan is an accomplished drag racer is a hell of an understatement. See this page
for a demonstration of HAMMER Dan's drag racing prowess.
Dan was one of my customers back then and we spent a lot of time together, mainly in the shop, working on his engines together. Obviously he came to know a lot about what we do and how we do it.
When I shut down that business, HAMMER Dan ended up with the machine shop side of it, and my salesman ended up with the retail side of it. HAMMER Dan is quite the accomplished head porter and engine builder. In fact, I have him do all the race heads for my Bonneville bikes, and he's been doing them for me for several years now. Many of the Bonneville records I've set were done with his head work. As most people know, there's another well-known shop that also benefits from HAMMER Dan's expertise
From the day he bought the machine shop, HAMMER Dan and I have continued to develop the processes and CNC technology. Basically, we've tried to automate as many steps as we can. Anything you can do on a CNC machine will come out with more consistency and quality than doing it by hand, that's just a fact. But the CNC has limitations as well, limitations we've worked very hard to overcome. Dan is the expert on head prep and I'm the code monkey and together we work to make the best process we can, so that we deliver the best product we can.
This is one of the first steps to get done to any set of heads. Once they're stripped and inspected, they're put into the 4-axis CNC machine in this position to get the seat work done.
Well, there are a lot of possibilities on this step. What size valves are the heads getting? What's the current seat i.d.? What kind of head is it? Is it a front or a rear head? Will it need new seats?
The problem here is that there are SO many possibilities, that keeping a separate CNC machining program for every one of them would be next to impossible. You'd have thousands of programs to choose from, and you'd have an error prone process. So here's our solution:
HAMMER Dan and I developed this program specifically to perform all seat operations. Basically, you enter all the information, and hit the "GENERATE CNC CODE" button down at the bottom of the screen, and the program goes off and writes the CNC program and then offers to send it to the machine. HAMMER Dan then punches a few buttons on the machine to get it ready, and hits OK, hits the "Start" button on the machine, and off it goes.
The top line in this program takes in info about the customer, as the program keeps a log of everything done to every set of heads. Head type and which head (f or r) is chosen next.
Then on the left you have everything to be done to the intake seat and on the right is the exhaust seat. You typically start by doing a "locate" operation. Since heads vary from one to the next, this step allows you to use an indicol to precisely locate the center of each valve. Once it's located you then set it up to do the cuts. You can cut and shape the seat, blend and unshroud it into the chamber, remove the seat completely, and/or cut a new seat pocket whatever size you want.
When HAMMER Dan cuts the seats at this step, he intentionally leaves a little material in them, because later he'll cut them again with the actual guides. But for now, he rough cuts them in, then removes the stock guides, and moves on to cutting the ports:
Again in 4-axis mode, the machine cuts the ports to the proper size and shape. But just like the seat operations, there's a dizzying array of possible combinations in terms of what you want the machine to do. So naturally we created a program to sort this out:
This is our main porting program. But it actually does a lot more than just let you select operations. If you choose the "Sledge" mode as shown, the program allows you to enter application specific parameters, like the bore, stroke, rod length, target power peak rpm, and cam timing. The program then goes off and does a bunch of math to figure out the ideal port size, and dynamically generates a CNC porting program to cut the port that size. This overcomes one of the big, big limitations of CNC porting, the ability to custom tailor the port to the application. It's the best of both worlds, you get the accuracy and repeatability of CNC with the custom capability of hand porting. I'm not aware of any other shop that has anything else like it.
Once that's done, HAMMER Dan does the hand blending. There's a fair bit of variation from one head to the next, and also there are some areas in the port where the CNC can't reach well. Dan is very talented and experienced at smoothing the variations and shaping the places the CNC can't reach.
Once the ports are right, Dan presses in new guides, sizes them for proper stem clearance, runs them through the machine again to get the seats to the final size with the final guides, and then puts the final valve job onto the seats:
During this step he also sets the stem protrusions for the correct geometry and proper valve to valve clearance. We use specially shaped seat cutters of our design on the seats themselves. We've found this process to work much better than using stones or other methods. The seat profiles for the two valves are very different as well, as their functions are different. For example, the exhaust seat has a much wider 45 degree area because one of the important functions of the exhaust seat is to pull heat away from the valve.
Any chamber work the heads need is performed as well:
This head is getting an angled squish band in the CNC machine.
And you guessed it, we have a program for that, too:
This program is also used for cutting the deck, which goes hand in hand. Ignore the valve seat stuff, we created the aforementioned program and no longer cut seats with this program. Also note the mentions of external head drains, the programs do this for us as well.
HAMMER Dan will iterate on this step until he gets the chamber size right where he wants it, to give the customer the compression ratio he wants:
And of course, EVERY head gets flow tested before it leaves the shop:
Finally, once the heads are perfect, HAMMER Dan assembles them with the finest hardware available:
The springs are of course shimmed as needed for the proper installed height, to give the required seat pressure and travel.
And finally the heads are ready to go back to the customer:
This process has served us well. HAMMER Dan runs hundreds of sets of heads through his shop every year, and has proven time and time again to deliver a superb quality product that performs exceptionally well. I'd wager HAMMER Dan has put more XL's over 100hp than just about anyone out there.
If you'd like to treat your heads to this process, give HAMMER Dan a call at 970-344-7120.