| Author | Message | ||
     Sportyeric |
People are commenting on the blue smoke. Guess I can't procrastinate any more. What then do the wise here think about a value-for-the-money rebuild of my S1 engine (motivating my cafe'd Sportster.) I've read elsewhere the notion to put T-Storm pistons in the S1 heads, with the head clearanced for a squish area that would allow 11:1 compression. For an engine that doesn't normally get revved over 5500 but likes to live between 4000 and 5000, does this seem feasable? Would a rebuild on heads with 60K miles be cheaper than buying T-Storms? (I'm assuming some guides, maybe not valves, etc.) The smaller valves of the S1 heads should make better velocity at moderate revs while the dome gives good squish. The chambers should be able to be enlarged enough to correct the compression, yes? | ||
| Aaron |
What you're talking about doing, cutting a 15 degree shelf into some Lightning heads and matching that up to 15 degree Thunderstorm pistons, is all about giving yourself a squish band. A stock S1 has no squish band because the head has a 10 degree shelf and it's a flat top piston. You'll likely have to do some chamber relief to get that down to 11:1 but it ought to work better than the stock arrangement. The problem is, all this chamber work, plus a valve job, costs money. Think carefully about how much money you're willing to put into that set of heads, particularly considering you can get a set of XB heads for under $600 and get a far superior piece. The XB heads have a 62cc chamber just like your Lightning heads, but they have a pair of flat squish bands. So they give you 10:1 and squish with stock flat tops. They also have bigger valves and a much better port design on both sides. I've seen enough data that I'm pretty confident in saying they're worth 5-6 more hp over Thunderstorms, stock to stock. I don't see why anyone still does Thunderstorm conversions. | ||
| Phillyblast |
Aaron, would the same apply to the S2? I'm assuming a matching set of cams would be required/recommended to see some real benefits? David | ||
| Torqd |
How confident are you in the front motormount...having to oval it out for the XB heads? | ||
| Sportyeric |
Cost is a bigger factor than high-rev power. I'm going into this from the likely position of having to go to 10 thou over pistons so its not a cost savings to stick with flat tops. A little extra spent on the shelf cutting, if I do the chamber relief myself, might be good value compared to simply rebuilding to stock. I was following your early results on the XB heads, Aaron, but have to get back to the archives for a refresher and update. Stock rockers and covers still work, don't they? I guess I really have to wait 'til I pull the heads and see how much work needs doing on them, see if there's too much worn to bother with. I may be exceeding the bounds of my competence thinking about doing the relief work myself. I guess the amount to be removed would almost be the size of the dome on the piston, wouldn't it, since there is a shelf in there already? Less the bit of shelf removed and less the increased compression made possible. Hmmm. The original 883 to 1200 conversion involved simply dremelling the 883 bathtub to the hemi shape of the 1200 (S2). Pinging was a big problem there. I wonder, though, why the Moco kept using the S1 head in the Sportster Sport while using the T-Storm for the M2? I believe you all rev the Buells higher because of the rubber mount. So is the S1 better at mid-range? If the T-Storm is better down low as well, is it due to the squish? Would my idea combine the best of both worlds? Given the improved port design of the XB heads, I might re-state the original question substituting XB heads for T-Storms. edited by Sportyeric on September 04, 2003 | ||
| Aaron |
David ... yes, since S2's also use flat tops. I haven't tried'em with stock D cams, but hey, Thunderstorms work well with D cams, look at all the good running M2's out there. Frank, I don't have to oval out no stinkin' front mount, I have a CNC machine   | ||
| Aaron |
Eric, yes, stock rockers and covers are no problem. What you'll run into with cutting the squish band is that you'll first have to cut .030 to .040 off the deck, because there's a big lip there at the edge of the chamber, down to the squish shelf, and it won't be very even due to the core shift. That cut will push your CR way up. As far as the relief goes, do it in a way that unshrouds the valves as well as helps overlap flow. It really helps to have a CNC machine, it can do it in a controlled manner. No, S1's don't have more bottom end or mid range than S1W's. This gets into a whole bunch of controversial theory about port design and valve sizes that I don't want to get into. But there are a bunch of big valve XL motors in this world that make power over a really wide range. As to why they kept using XLH1200 and Lightning heads after T-storms came out, hell if I know. | ||
| Jssport |
Aaron, I thought the XB heads were the same on both the 9 and 12 models, and the pistons on the 9 had a dome whereas the 12 was flat topped. Is this correct? Then wouldn't the 9's dome give problems to a head built for flat pistons ? (Actually I was thinking about using 9 pistons in a 12 to raise compression) Aaron said,.... >>>>>>>>>>>>>>>>>>>>>>> The XB heads have a 62cc chamber just like your Lightning heads, but they have a pair of flat squish bands. So they give you 10:1 and squish with stock flat tops >>>>>>>>>>>>>>>>>>>>>>> | ||
| Sportyeric |
Thanks for the input, Aaron. It's seeming beyond my abilities, technical and financial. I don't have a CNC machine or a digital camera, but I am working on what I hope will be a better looking motor mount than the stock Sporty unit.  | ||
| Aaron |
Jim ... yes, the XB9 and XB12 use the same heads, the XB9 has a domed piston and the XB12 uses a flat top. No problem with the 9's dome, it's shaped to fit up inside the bathtub chamber, i.e. rectangular. Yes, 9 pistons in a 12 is a simple way to raise the compression to race levels. Personally, I'm more a fan of angled domes, i.e. cutting the flat squish bands to say a 30 degree angle and using a regular 30 degree domed piston (that's what I did in my 121hp XB headed M2). Flat squish bands with a domed piston (i.e. XB9) creates an obstruction to the fuel being squeezed out of the squish band, where an angled squish band directs it at the flame front with nothing in the way. Also, an angled squish band allows a more direct path for incoming fuel flow, it doesn't have to go around a big ledge to fill the cylinder. Man, Brian's gonna shoot me if I don't shut up "> But none of this is that big of a secret, most head porters worth the aluminum chips in their ears know this stuff. edited by Aaron on September 04, 2003 | ||
| Jssport |
So the 9's piston is a dome but with a flat-top squish band? So,.. do the T/S 1250cc Hurricaine pistons fit up to the XB heads, or are you doing what to get that 30 degree squish band. Don't worry, this thread is so far buried nobody will gleam this info ... hehe | ||
| Aaron |
Yep, that's right, take a look, here's our XB9 1050 kit Hurricane pistons ...  They're designed for the stock XB chamber:  But we offer that piston in both 15 and 30 degree domes as well, in a variety of dome heights for various compression ratios. Other folks have'em too, but they're not as good as genuine Hurricanes Here's an XB head after cutting it to 30 degrees in the CNC machine:  Thunderstorm heads and pistons are 15 degree as delivered, I *think* that's a 15 degree 1250 kit Hurricane piston on the far left in this picture:  Could be a 30, hard to tell, it's been awhile since I took the picture. Looks like a .125 dome. Again, a lot of customers have us cut their Thunderstorm heads out to 30 degrees and go for 30 degree Hurricanes, and we offer them in various dome heights. | ||
| 57sporty |
Aaron, Those XB heads look just like the Edelbrock 1200 RPM heads. I have those Edelbrock heads on my 88" motor that I have in my Sportster. I am running the 62cc chamber with flat top pistons. Are these the same heads? I recently rebuilt my motor due to bearing failure on the front rod. Steve | ||
| Aaron |
Wow, by my calculations a 62cc chamber with flat tops at 88" would yield almost 12:1 compression. You running that on the street? Maybe you lost that rod bearing due to detonation? No, the XB heads are HD/Buell's creation, at least that's my understanding. They have a very unique intake port in particular, a big floor. | ||
| 57sporty |
Aaron, I do run it on the street, but not on long trips. Just around locally. I haven't noticed any detonation. I run a vthunder ignition and am running a max timing of 28 degrees. I may be looking at getting the Edelbrock heads ported. Have you done any of these type of heads? Also what cam reccomendations would you suggest. I am running this bike street/strip AMRA. I want to get more involved in the events next year. My bike broke on me at the strip and both thrust washers were loose and spinning when we tore it down. The front rod bearing went and caused the rod to spread against the wheels. Therefore, locking the motor up. We set the clearance on the S&S rods little on the loose side. I also went .010 over on pistons. The bike runs better than before. | ||
| Aaron |
Steve, keep in mind that detonation isn't always audible and rod bearings is one of the major things to suffer. Absolutely we have experience with Edelbrock heads. Let us know if we can help you out. Bigger power is available from heads that take advantage of the big bore, though. As far as cams go, we've done motors around a variety of grinds, and the Red Shift 585's are a sweet grind for all-around 88 inchers. They have a late enough intake close to accomodate compression and make power and they're modest enough on the overlap to work with street exhaust systems. Yeah, they're pricey, but they work well and they don't beat the hell out of the valvetrain like some grinds do. You can make reasonable power with'em, even with OEM heads made for a 3.5" bore ...  (this is Torqd's 88 incher) If you send us the heads, just make sure Brian knows what cams you'll be using, it's important to how the heads are prepped. | ||
| Aaron |
Oh, to elaborate a little on what I was saying with respect to heads that take advantage of the big bore ... Brian frequently gets intake flow in the 160 to 165cfm range at 10" out of Thunderstorm or XB heads (not that flow tells the whole story mind you). He did a set of 3-13/16 bore heads recently that flowed 220cfm at 10". | ||
| Jssport |
Excellant info Aaron,.. thank you very much | ||
| Torqd |
Well that ain't the mount you started with:-) So are you guys going to market that mount...what is the going rate going to be...I guess that it is a LITTLE bit better than ovalling out the stock one:-) | ||
| Torqd |
uh...scratch that last ? Aaron...I haven't been to your site for a day or two... | ||
| Rippin |
Aaron , You've got mail. Thanks Ryan |
