| Author | Message | ||
     Not_purple_s2 |
I'm wondering what advantage newer heads have over older heads when they're worked (ie Stage 2, Stage 3 head work). Example; My S2 heads are basically stock sportster heads, but with Stage 2 head work (1.760/1.530 valves and CNC porting) I would expect them to perform better than switching to stock XB heads for basically the same money. Yet, I see alot of people on the board endorsing the XB head swap. I don't see how one could swap to XB heads for much cheaper than the $850 for Stage 2 work. I think there was a discussion of this before but I couldn't find it. | ||
| Firemanjim |
Your S-2 heads will need big work to get them to exceed the XB stockers.Give Brian a call at Rev-Perf.But that said if you are not going to big cams etc,and just want a bit more from your S-2,go with stage 1. Aaron did one of my S-2's that way and it was a great ride. | ||
| Not_purple_s2 |
I was just noticing that the NRHS website shows smaller valve sizes for their Stage 2 XL heads (which I assume mine would be). Are the S2 heads incapable of taking 1.850/1.615 valves? If so then I guess that would be a good reason to step up to the XB heads. Revolution Performance's site doesn't say anything about smaller valves for XL heads. I just figured that using my stock heads would save a good bit of money since I'm looking to have either heads worked anyway. | ||
| Sportyeric |
The stock heads, lacking a squish area to prevent pinging, have a compression ratio of, I think, 9:1. All the heads that came after (Lightning, Thunderstorm, and XB) have at least 10:1, made possible by superior combustion chamber design. No amount of porting is going to get you past that. There is a relationship between valve and port size and mid-range power. Putting in as big a valve as you can fit will give you maximum top RPM horsepower but will adversely affect mid-range. Know what you want. As glamourous as "worked" heads are, I think common wisdom is, as you've said, that stock XB's will outperform worked S2s at any RPM. Do keep in mind that the XBs require the purchase of a custom front motor mount. (Which is a beautiful piece of art.)(No. I don't have one.) | ||
| Djkaplan |
"No amount of porting is going to get you past that". I remember reading (years ago) that astute tuners would start with 883 heads over 1203 heads because of the squish issue. What's your opinion of reworked Thunderstorm heads over reworked XB heads? I already have an NRHS billet mount for the Thunderstorm heads... I'd hate to have to buy another. | ||
| Sportyeric |
I also remember years ago reading in Hot XL magazine about Bob Johnson at Johnson Engine Techologies (a Badweb sponsor, BTW) getting huge power out of re-worked 883 heads that kept the stock 883 size valve on one end or the other. He probably has better technology now. Aaron Wilson gave a great summary of the merits of each different head in a posting at Sportster.org that I may try to dig up a little later, perhaps. As I remember, the XB heads have a different port shape that is more optimal to begin with in a fashion that Thunderstorm heads can't be modifed to match. Plus the valve spring design allows higher RPM. Like they say, "Speed costs money. How fast do you want to go?" You can probably flog the billet mount for half your money back, but its still a couple of hundred extra, I'd guess. Give me half a year and I might buy it from you. | ||
| Sportyeric |
Aaron's write up is here: http://www.sportster.org/cgi-bin/lwgate.cgi/XL-LIS T/archives%5Cvolume2004/677/date/article-13.html |
