| Author | Message | ||
     Jayvee |
OK, looking (again) at the Hammer 1275 kit, and looking at adding ported XB heads, to my 2000 M2. Would this mean I have to replace the Thunderstorm rocker boxes and covers with XB parts? Or can I use the Thunderstorm rocker boxes and box covers? I'd have the carb mount holes drilled anyway, so my existing breather system could work. This was probably covered previously, but my searches don't answer this specific question. Cheaper to just port the Thunderstorm heads, but XB heads are described as 'the best' on Hammerperf site. | ||
| _buelligan_ |
The "best" stock platform and will perform the "best" at little to no head work. If you plan on doing their sledge head job, it doesn't really matter what you send them. 883 heads were performing just as good as XB heads at that level. You should still be able to run your thunderstorm rocker covers with XB heads. | ||
| 89rs1200 |
Thought they removed the head breather porting out the carburetor mount bolts on the XB models. If that is the case, then the XB rocker boxes and covers and PCV valves will be needed for that blow by to get out. | ||
| Upthemaiden |
Keep in mind that on top of the cost to buy the XB heads and have them ported, and having them machined to work with your umbrella valves, you'll also need to buy a new front engine mount to fit onto a tuber frame. If you're not worried about the cost of it in any way, please continue with your current plans and just send me your thunderstorm heads for my S1.  | ||
| _buelligan_ |
The raw casting bosses are still there on the XB heads for the side breathers, so if he were to use XB heads on the M2 they would need to be drilled, tapped and then machined flat. | ||
| Normthenomad |
'04 Sportster heads are essentially XB heads with the ability to use a carb and already have the nose breather holes drilled and tapped.Good for about ten horse power over Thunderstorm heads. | ||
| Upthemaiden |
That's some good info Norm. Is there a preferred piston that you want to use with those heads? just use the matching sportster pistons, or are the XB pistons a better match if you're looking for the power increase? It's so weird to think after all this time we're talking about using sportster parts to get more power out of our Buells... | ||
| Normthenomad |
Believe I'd run XB12 pistons it's a flat top piston and gives a 10:1 compression ratio, the XB9 piston is a flat top as well but pushes the compression ratio to about 12:1. Both are the same bore size. XB9 has shorter stroke. | ||
| Phelan |
The Thunderstorm heads once ported are just as good as the XB heads and require less additional parts to fit. The XB heads require a different front mount (which Hammer also sells, but at $230 IIRC). XB heads also need the breather holes drilled and tapped for the car support mount. You can use the stock head bolt breathing and stock rockerboxes and lids with stock or XB heads, but replacing the top 2 piece lids with the XB 1 piece lids and PCV breathers, and replacing the hollow car support breather bolts with standard solid bolts. | ||
| Upthemaiden |
"The Thunderstorm heads once ported are just as good as the XB heads" How do ported Lightning heads typically compare to ported Thunderstorm heads? Are they going to end up in pretty much the same place at the end, or is it still worth tracking down a set of the Thunderstorm heads if you're going to send them in to get work done? And when you say the ported Thunderstorm heads are as good as XB heads, I assume you're referring to stock XB heads? | ||
| 34nineteen |
How do ported Lightning heads typically compare to ported Thunderstorm heads? I would imagine the two compare pretty closely if the same porting work is done between the two, especially as you dive deeper into the more extensive porting work. After reading Hammers site about heads and porting, they call out 883's as being pretty bad out of the box, but seem to have no problem extracting a boatload of power after modifying the heads. I was considering going to an XB setup, but then decided that I wanted my S1 to have a more "period correct" look. So I stuck with the stock non-Thunderstorm (Lightning) heads, but had them ported. (Message edited by 34nineteen on December 14, 2020) | ||
| Upthemaiden |
I'm not too concerned with period correct, but if I get pretty much the same results from sending in my 97 heads, as I would from buying thunderstorm to have ported, or just buying XB parts for my bike, I'd gladly take the cheaper option. | ||
| Screamer |
There was a claimed (by the factory) 10 hp increase from a Lightning motor to a Thunderstorm motor, although a portion of that increase came the collector going from 2” to 2.5”. On back to back dyno testing, we found that the .5” increase on the collector diameter was worth about 2 HP. The 2” and the 2.5” collectors that were compared, both had the shorter stock length primary tubes - not the ~36” primary tubes that the “race header” used. Also, the measured static compression ratio on the Lightning package was usually 9.7- 9.8 /1, and the Thunderstorm package typically measured at a true 10/1. So subtracting the potential 2 hp from the collector change and a possible 1-2 from the compression increase - from the claimed 10 increase, would still leave about 6-7 for the change in heads alone. On one of my S2 models, the best we ran was about 87HP at the rear wheel - With SE bolt-in cams, and ported and milled S2 heads. Later, on the same engine with flat-top pistons, CV44 and ported and milled T-Storm heads - would run 100-101HP at the rear wheel. Again, the carb and compression increase might account for about 5HP, but that would still leave about 7-8 for the heads. So,,, without valve and seat size changes, Thunderstorm heads could/should produce about 6-8 hp more than similarly modified Lightning heads. I’ve heard from reputable sources, that moving from T-Storm to XB heads produces a similar increase, but I haven’t had any “back to back” opportunities to confirm it. | ||
| Normthenomad |
'04 to '06 XL 1200 heads have the same combustion chamber as XB heads and will accept a carb and already set up for nose breathing. 883 heads are limited so far as oversize valves and still have the hemi combustion chambers. | ||
| Normthenomad |
Hammer Performance has lots of dyno charts with head to head comparisons on just about any combination you can think up. |
