Author Topic: HAMMER PERFORMANCE 120+ Horsepower 883-1275 Bolt-On Conversion Package  (Read 2595 times)

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Offline aswracing

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Man, it's been a long time in development as we've had to solve one problem after another. But we're finally ready to release it. Here's a result we got yesterday:



This is our shop mule 2007 XL883, equipped with the HAMMER PERFORMANCE 120+hp 883/1275 conversion package, consisting of:

Disclosures:
  • CCP is 200psi on both cylinders and it's running on pump gas.
  • I had no air cleaner in place for this pull as the one that comes with the HPI throttle body is too small. I'm going to work on a version of our Air Hammer air cleaner to fit it, but I don't have it available yet.
  • This was a 5th gear pull. I did not do any 4th gear pulls.

SLEDGE+ service in this case means we welded up the floors so we could do a proper short side. Also, we altered the valve angles so that we could fit 2.020 intakes and 1.630 exhausts. Valve stems are 7mm. Here's a chamber pic, I ain't showing a port pic  :SM:



To complement the wider valves, we increased the bore size to 3.600". It works out to 77.6ci. It's still a bolt-in, no case boring required. Here's a picture of the kit:



For the time being, the 1275 bolt-on kit is going to be exclusive to the 120+ package. Reason being, it's more expensive, and therefore best suited to the guy who wants every last horsepower. I don't know that we'll ever be able to make it cost-effective for lower power applications. It's just inherently more expensive to make. We're kind of seeing the same thing happening in Twin Cams with the 110 bolt-on kits. They cost so damn much money that for many people a 107 makes more sense. The Sportster market is more cost sensitive than the Big Twin market, too.

Those were the two big things we did to get to this level, the altered angles/bigger valves and bigger bore. We also used the HPI 51mm throttle body as we're outrunning what we can get from the stock throttle body at this level. Likewise, we found some power by going to 1.725 ratio rockers. Late model XL's, 2006+, have a funky plastic anti-rotation device for the lifters and it sets a ceiling on lobe lift. By adding lift at the rocker side, we were able to avoid that issue.

We basically developed the two ideas independently, and then finally tested them together for the first time yesterday, which is when we got the above result. Then we tore it down again to make sure everything survived the punishment. It all looked perfect.

Neither of these two ideas worked the first time we tried them. Just punching out a 1250 cylinder to the 1275 bore size caused cracked spigots immediately. So we jumped on the steel liner bandwagon ...

 

The liner is 120,000psi tensile strength. The spigot is thin of course, but the working area of the cylinder still has a thick liner as you can see on the right.

The widening of the valve angles and larger valves didn't work right out of the gate either. First experiment, we were losing control of the valvetrain big time at about 7400. The chart got choppy and when we took it back apart, it had beat the hell out of everything. The bigger valves were just enough heavier to push us over the edge. And we were already using the best beehives we could find, PacAlloy endurance springs that are heat treated, nitrided, shot peened, and stress relieved, with Ti retainers. Same stuff worked fine for us on the smaller valves.

We really, really didn't want to go to 5/16 stems and monster springs. We wanted this to be a street motor, which means a valvetrain with some longevity to it. Eventually we gave these a try:



This is a fairly new product, it's been out less than 2 years. Notice how it's a single wound spring, no dampener either. It's not a beehive and not a straight wound spring. The idea is that each coil has a different resonant frequency, so the oscillations from whichever coil is resonant at any given rpm is naturally dampened by the other coils. Supposedly, they're good for 400-500 extra rpm at a given seat pressure as compared to a beehive. I was skeptical, but I have to admit, they seem to meet the manufacturer's lofty claims. The valvetrain is stable to at least 8000, and we only increased the seat pressure a smidgen from where we had it with the beehives. I'm starting to think maybe they're onto something here.

But beyond the valvetrain control issues, we weren't seeing any additional power from the bigger valves, either. We were pretty darn sure though that it was because we had run out of space, and we were shrouding the short sides badly with the cylinder wall. So we withheld judgment on that until we could test it with the 1275 kit. When we put the two together, sure enough, it worked, we got more power than we got with the 1275 and the 1.980/1.610 valves.

So anyway, we finally got the problems solved and it easily met the numbers. Very first power pull after the mapping work was 129.5. Didn't take long to get the above. We like to be at least 10hp above advertised power levels, because we know not everyone is going to get everything out of that we do. If we're 10hp above what we're advertising, the customer has a reasonable expectation to make the number.

I've put a little blurb about it on our web site. I don't have pricing up yet, but I'm working on it.


Offline westcomb

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NICE SET UP!  :up: ............. My buddy is running a nice 1250 set up I bet he would have done the 1275 two years ago if that was a option! .......... I think he is about 120 HP right now ........... Fast strweet bike! its a good set up for sure!

Offline FordTechChase

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Very very nice. I purchased "Grinds" sportster from him last year when he listed it for sale here in OK. Yalls parts are top notch and work very very good. I believe that setup on that bike only does 110-111hp and it is an absolute blast to ride and revs way out there, pure music in the ear. I never really gave it much thought but these engines are tiny at under 80".

Offline aswracing

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Very very nice. I purchased "Grinds" sportster from him last year when he listed it for sale here in OK. Yalls parts are top notch and work very very good. I believe that setup on that bike only does 110-111hp and it is an absolute blast to ride and revs way out there, pure music in the ear. I never really gave it much thought but these engines are tiny at under 80".

Congrats on picking up Scott's bike! That's a special bike for sure. He was one of the first to get our 30 degree reverse dome pistons, and also one of the first to get one of our billet intake manifolds. In fact, I think he was THE first person to get a billet manifold.

I think we helped with that project in 2012 if memory serves. It was our latest and greatest stuff at the time. Of course, we've done a lot of R&D in the last 4 years and we've moved the bar much higher. But that's still a great package. 110hp in a Sportster is nothing to sneeze at, it goes like stink. Scott was a big help, too, in getting it sorted out.