Is it feasable to purchase a set of high compression "drop-in" pistons for my 04 1200?

I am sending out the heads to Nallin for Stage 2 modifications. The cams are .551" lift 'SE'.

The motor has 2,500 miles on it. Just wondering if I can intall a set of maybe 10.5 to 1 pistons, pins, and rings in the stock cylinder bores without any machine work to the bores? I just want to up the stock 9.7 to 1 CR without milling the head surfaces.

Thanks,
Ron

Or would I be better off purchasing maybe .020" oversize pistons and then having the cylinders bored and the pistons fit?

Still looking for 10.5 to 1 CR

Turbota

When you send your Heads to Nallins talk to Justin. I believe they can set you up with some 10.5:1 pistons...

G'day Ron

AS I said in the other thread...... go to an 0.005" over piston and get the bore squared up...

If ya sendin ya heads to Nallins then send your barrells and tell 'em what ya after and leave them do it......

cheapest way to do anything ... is by doin it the right way first time.... and listening to the guys that know is the first step..

Makes sense ...

Thanks

Yeah I even make sense to myself sometimes......scary init??? untill Saturday night on the piss anyway ;)

Here is a set of Hurricane forged domed pistons. A little pricey, but there good quality. With stock 04-05 1200 head chambers (62cc) they are supposed to give 10.5 to 1 CR. Looks like this may be the ticket. Nallin will bore and hone the cylinders and precision fit these pistons in them for $49.50 per cylinder.

I think I will just send Nallin my heads for a Stage 2 upgrade [and] my empty cylinders ... And then have a set of .030" over-bore domed forged pistons fitted in them.

Anyway, I'm going to give them a call today.

http://img.photobucket.com/albums/v248/Turbota/HurricanePistons.jpg

XL1200 Dome Piston with Valve Pockets
3.50" +.015" oversize
10.5 :1 Compression Ratio
002-P3515XL-DK
$299.95

XL1200 Dome Piston with Valve Pockets
3.50" +.030" oversize (1221cc)
10.5 :1 Compression Ratio
002-P3530XL-DK
$299.95

FROM THERE WEBSITE ..... "Since their introduction in 1998, countless records have been set, races won, and street riders satisfied with Hurricane Pistons from NRHS. Totally re-designed and updated with the latest in forging and piston ring development, you simply cannot buy a better piston for your Harley Davidson or Buell engine. Dual wrist pin oilers, light weight tool steel wrist pin, expansion grooves, and valve pockets that accept high lift cams and large valves are standard equipment on all Hurricane pistons.

We also pay particular attention to carefully matching squish configuration to the stock head, resulting in maximum power with a reduced risk of detonation. Your bike deserves the best: Hurricane Pistons from NRHS!"

I am very interested to see what you come up with for power when your done. Keep us posted as to progress.

Pulled it apart today:

http://img.photobucket.com/albums/v248/Turbota/DSCN0487.jpg

http://img.photobucket.com/albums/v248/Turbota/DSCN0488.jpg

Below is the pistons. The front was oil soaked and had heavy carbon buildup. The rear was ok.
http://img.photobucket.com/albums/v248/Turbota/DSCN0490.jpg

I am sending the heads and the cylinders to Nallin on Monday.

I would think that those domed forged Hurricane pistons would work fine (10.5 to 1 CR)

That may be just a bit too much.(sarcasm)

Here is some very interesting info I got in an e-mail from Art Northrup concerning Domed Pistons in a Buell headed 04-05 XL1200 motor:
_____________________________________________

"Domed pistons would not work with the new XB type heads. Thunderstorm heads needed domed pistons, but the combustion chamber design is different.

Contrary to popular belief, increased compression does not automatically = HP, but if you want to bump yours up a bit, here's a simple trick - use Bartell's .027" copper head gaskets (stock is .053") & no base gaskets @ all. Most people who do that use Yamabond as a sealer in place of the base gaskets, but I learned an even better trick - clear 50-year GE 100% silicone - yep, the same stuff you get @ Home Depot to caulk around windows, door & bathtubs with. The indy shop guy who told me about it uses it, even on his 150 c.i. Pro Nitro engine & if that won't blow it out, I don't know what will!

If you're @ 9.7:1 now, the thinner head gaskets & no base gaskets ought to put you in the 10:1 range & to still use pump gasoline, you don't want to go much higher. I sure wouldn't buy new pistons for another 1/2 point in CR.

And, I wouldn't use forged pistons in a street engine - I do in the race engine, but I don't have a choice in that application. Forged pistons grow as they heat up, so they have to be set up "loose" & they rattle like a bucket of bolts cold. They also wear the cyls. faster.

The hypereutectic alloy cast pistons don't expand like forged pistons do & I'm pretty sure that's what the engine came with. I'm not 100% sure on that, but nearly everybody has been using that type of piston in a factory application.

KB pistons are that type too, which is why I prefer those in a 883>1200 application, for example. They can be set up as "tight" as .001" piston-to-wall clearance, if you're real careful - most go with .0015". Forged pistons have to be set up with @ least .0025" clearance & while the difference doesn't sound like much, it is. Harleys are bad about the pistons rocking in the cyls. - trying to turn sideways - so the less clearance you can get by with, the better.

Anyway, unless you're made of $$$, you can keep the pistons you have & bump the CR up a bit using the gasket trick. The new heads flow better than previous versions & they need the flat surface of the piston to work right. Combustion chambers & pistons must work together & the XB chambers are designed for flat-tops.

With Nallin doing the heads, you'll pick up a good bit of power - that's where the power is anyway. Had a whole bench full of XB heads - I believe they got started working on the XB heads before anybody. In case you didn't know, our own Aaron Wilson has bought NRHS - You'll be pleased with their work - Aaron's a stickler for detail".

Art Northrup,

If I do mine, I want to use the 1250 jugs but with the stock 1200 pistons. I like the slappy, metal sound.

Turbota

Interesting Read!!! Who is Art Northrup?? Should I know who he is??? :D

What I really found interesting was about the Domed pistons!!! When I talked to Justin at Nallin's just this past week, he told me that they use a slightly domed piston in their 1250, XB head conversion the one I'm thinking of getting!!!!

Why the heck would you use stock 1200 pistons with a .070 overbore. I am curious because it does not make any sense. The slappy metal sound is the sound of your engine wearing out really quickly. I am really curious what you have to say about that. 50cc is going to get you about what? 2-3 H.P. if that.

Damn, those pistons look a lot like the ones I had Ross Piston Co. make for my 86 - 1100 heads quite a few yrs ago. :wonderlan Lots of compression for racing.. Thirty thou over for a new engine? I hope Nallin tells ya no!! :clap Five thou should be the first overbore if the cylinders are ok from the factory. :rolleyes: Best advice came from Stevo already. Talk to Nallin and nod yur head and go uh hu a lot. :shhhh Listen and put it back together as Nallin tells ya to.

Why the heck would you use stock 1200 pistons with a .070 overbore. I am curious because it does not make any sense. The slappy metal sound is the sound of your engine wearing out really quickly. I am really curious what you have to say about that. 50cc is going to get you about what? 2-3 H.P. if that.

That's if the thing would even fire up!!! :yikes

Why the heck would you use stock 1200 pistons with a .070 overbore. I am curious because it does not make any sense. The slappy metal sound is the sound of your engine wearing out really quickly. I am really curious what you have to say about that.This increases volume allowed in the cylinder. The pressure of the expanding gases in the cylinder will hold all of the oil down in the case where it ought to be and the oil trying to get up into the cylinder will keep the air-fuel mixture from getting down into the case. The fact that this has eaten up four engines has more to do with creating more horsepower than the engine is rated to handle than the loose pistons beating the crap out of the insides of the jugs. It does do some damage but that is the cost of more horsepower. Anybody want their engines worked on? Send them to me!
:laugh

That's if the thing would even fire up!!! :yikesWhen dealing with this kind of power, you don't need ignition. I just roll it down the hill in neutral and just run the starter. I love the sound of Harleys! Clank-ta-to clank-ta-to.
:D

FWIW, I think that I could achieve a similar performance from a 1200 that I could from a 1250 assuming that I am working with similarly performing components. Honestly, with carb work, I am putting out as much hp and torque as a new sporty or BT but with a little more snap. If I do a little more with the heads and what have you, I know this bike would be nothing to sneeze at. ;)

O'k Barry, I guess you really want those sloppy pistons in the bigger cylinder. I don't think I will have you build my motor though. I like the minimum clearance suggested earlier. Mine runs faster than every Harley I have come up against so far(someday that will change and I will get beat, but not yet). I am still not sure that pistons that are incredibly loose will even work unless it is in a dragster and gonna really expand the pistons a bunch. I think you mean to keep stock bore 1200 pistons and cylinders. I think I misunderstood you because .070 gap between piston and cylinder would be excessive to say the least. If it floats your boat though then have fun. Maybe when I get to Atlanta eventually for work again we can run them and see whether that really works. If so I will start listening to your logic more carefully. Till then I am going with what I think I know.

LOL Barry.

Hey Ralph, I think he is yankin your chain just a bit. LOL

LOL Barry.

Hey Ralph, I think he is yankin your chain just a bit. LOL

You reck'n!!! :yikes

OK guys a few points before this thread gets no where near where it started.

Art is the engine guy behind a few of Crims records...He knows his shit.... George will correct me if I'm wrong on this but I'm pretty sure a few were done with Arts engine and he can fill ya's in on which records were which.
I think he's the other guy in Crims avatar...Unfortunately I havn't had the pleasure of sittin down a discussin engines over a few beers with him so I don't know.


I think Arts missuderstood what Ron sent him in the email that he's replied to......

What is commonly refered to as "Domed" pistons WILL NOT work with the XB heads unless ya machine 'em for it, which negates some of the benefits of the XB style head.
The pistons shown in the beginning of this thread are a "raised centre" piston designed for the XB style heads...These are the ones that Ron is refering to.

Hypereutectic pistons are a better way to go for street use but I'm not sure what's available for the XB style heads yet...ya need ta have a chat to another Ron, this one is Ron McBroom ...he's the head piston tech/guru at Keith Black...and he's a guy that REALLY knows his shit.


Use of a 0.027" head gasket is a good idea IF ya have a zero or plus deck height.
The change to a .0.027" head gasket AND removal of the base gasket will probably bring your quench height down to around 0.015" ...... BANG.... exit engine stage left...

Absolute minimum quench height should NOT be less than 0.027" and even at this height the engine MUST be warmed up to FULL operating temp WELL before revving it.
With these low quench heights the motor MUST be used hard or you will get carbon build up and engine longevity problems..

Art's advice is correct BUT he's assuming that the person using that advice is going to follow all the correct advanced performance engine building techniques and measure EVERYTHING...... unfortunately with this net thing a lot of people read too much and skip a few key areas...whoooooopps BANG...

LOL Barry.

Hey Ralph, I think he is yankin your chain just a bit. LOL
HAHA! Yeah. Sorry, I thought everyone would just assume. hehe. Just for the record, I would never do that. hehe.

Stevo, or someone else could you please explain ( quench height ) ?

Quench is the area between the piston and head OUTSIDE of the head volume area. In other words, if you have a 3inch combustion chamber and a 4in piston, the area on the outside of the combustion area, 1/2 inch all around, is the quench area. On the XB heads the combustion chamber is kind of bathtub shape and on 883 heads its round. When you pull a head off and you see a small black circle around it, that is usually the quench area.
Usually the quench height is the gasket thickness plus any - deck height. Some companies like Nallins angle the combustion chamber to force the compressed charge into the chamber for a more efficient burn which I believe reduces the quench area.

G'day Kyle

There is a number of "heights" refered to in engine building.

The deck height is the distance between the top of the piston and the deck of the block, top of the block or barell.

The distance between the piston and the head is refered to as Quench or squish height as it is the area of the Quench/squish band.

When the piston comes up to the top and nearly meets the head an area around the outside if it is less than .0.060" or so will not allow combustion to take place.
This is called a Quench band because it quenches the flame or a squish band because it squishes the the charge out of there and pushes it into the middle of the combustion chamber.

A low quench/squish height works on a number of levels for improving a controlled burn.

By pushing the charge from around the outside of the bore into the middle it bashes more fuel particles against each other and gives better fuel homgenisation.

By reducing the height to a point where combustion can't take place it forces the combustion to start in the middle and the flame front to move out from there.
The more controlled the burn the more energy from the burn will be transfered to the piston as usable force.

A low quenc/squish also helps eliminate pre-ignition which typicaly (but not always) starts in hot spots around the periphery of the cylinder.


Is that what you were after or have I just made it worse???????? Ya should try talkin to me in real life, most peoples eyes roll over after a minute ;)

Yup, what Stevo said. :clap Another thing about those domed pistons pictured in an earlier post. Those domes will probably hurt flame travel. The flame front likes a flat piston and a wide quench/squish band. Those pistons just pop up into the chamber. They will give more compression, no doubt, but at a cost of flame travel efficency. Nallin can fit you up with 20º or 30º domed pistons and machine a matching squish shelf in your heads when they do the portwork. I think they even show something like that on the Nallin web site. Like I posted earlier, talk to Aaron and tell him what you want the engine to do, then :shhhh be quiet and listen.. :smoke

I think I am going to have to take my bike to Atl. on my annual pilgrimage to Alpharetta to race you now Barry.(after pulling my chain and all(its a belt by the way)) I will get to see if all the engine knowledge has been useful. I think I will probably be kickin your ass but who knows. Maybe I will be eatin crap instead but I doubt it. Can't wait to meet. Going to Daytona? I could go thru Atl and pick you up. Daytona is about 5 hours from there at 100 mph.

Reply from Art Northrup:

If it was me, I'd be calling KB:
http://www.bcheads.com/kb.htm

My last project was an 883>1200 conversion & I got .005" oversized KB295
flat-top pistons, Zippers tool steel wrist pins & Total Seal rings. Total
piston weight is actually a tad less than stock 883 pistons & with the
"tight" setup & Total Seal rings, blowby & leakdown is -0-. That engine
ought to run 60,000 miles easy - that setup has before. Also, those
pistons are the "deep pocket" version so you can run more cam & not have
the valves hitting the pistons.

There's a guy on the List who goes by "Panman" & although he rarely posts,
I'm assuming he's still around. He's the guy who designed the KB pistons -
he's a real smart engineer (of course, so am I ;-)} Last time I chatted
with him, he was saying that some new versions were coming out, so although
I don't see pistons for XB heads listed on the website, they probably
already make them.

I personally would not use the domed pistons in a street engine. Nallin's
may disagree with me on that, but the XB heads will flow like a champ with
flat-tops, there are no flame-travel problems & there's another deal -
domed pistons tend to push the mixture to the edges of the cyl. & cause
more blow-by. In severe situations, I've seen the edges of the pistons
burnt off down to the 1st ring. The trick is to concentrate the mixture
right smack in the middle of the combustion chamber, as close to the
spark-plug as possible. Then you can slow the timing down & never worry
about "pinging" as the cyl. efficiency is really good. I'd give up some
compression to make the volumetric efficiency better. Get me to 10:1 on
the street with good heads & flat-top pistons & I'm a happy camper who can
buy gasoline anywhere. That's also why the "reverse-dome" pistons in a
basic 883>1200 work so well - the dish in the piston matches the shape of
the combustion chamber & the mixture is concentrated right in the middle of
the cyl.

The race engine is a whole different ballgame - 13:1 compression, huge
valves, .715" lift cams, domed pistons. But, the heads are Zippers billet
heads, cut on a 5-axis CAD-CAM machine & the pistons we get as JE
"blanks" - flat-tops with way too much material above the rings. Those
pistons are then machined to match the hemi type heads, EXACTLY. They have
to be set up "loose" as they do grow when heating up & the powerband of
that engine is 5500-7200 rpm. With Total Seal rings, blowby & leakdown
is -0- when the engine is up to operating temperature, but not when the
engine is cold. It likes 108 octane leaded racing gasoline the best,
although I have tried 112 & even 116. Last time I bought any, it was
$5.75/gallon - God only knows what it is now.

The point I'm trying to make is that what works on the racetrack does NOT
necessarily work on the street & I would never try to run such an engine on
the street. On the track, I don't care about power @ 2500 rpm, but on the
street I sure do. On the street, I want to be able to buy gasoline
anywhere - @ the track I don't have a choice - the rules require I buy it
there.

To use a domed piston, you really have to match it to the combustion
chamber, flame-travel can be a problem & so the timing has to be advanced
sometimes (Ironheads are really bad about that) & you really have to make
sure the valves with high lift cams aren't getting too close to the
pistons - valve stems do stretch @ higher rpms. I haven't personally
worked with the XB heads, but from what I've seen, mildly worked XB heads &
good flat-top pistons make for a great street combo. Decent compression,
but more importantly, good volumetric efficiency with a lot less turbulence
inside the cyl. "Squish" that mixture down into the combustion chamber,
light the fire & off you go.

The best design I've ever seen was on my FZ Yamaha - it had 11:1
compression & would run on regular gasoline. How did they do that? The
combustion chambers were a hemi type design, but the dish was very shallow.
The pistons were slightly dished too & when the piston was @ TDC, the
piston & combustion chamber formed a perfect ellipse. The spark-plug was
right smack in the middle of the combustion chamber & each cyl. had 3
intake valves & 2 exhausts. That's what I call "volumetric efficiency"!!
Get a LOT of mixture in there, then squish it down right smack in the
middle of the cyl. so when the fire starts, it pushes down right on the
center of the piston.

Can't do that with a Sportster, unless you're a millionaire, but you can
follow the same train of thought. Use flat-top pistons & get the ports &
combustion chambers working as well as you can. Concentrate the mixture in
the combustion chamber, right by the spark plug & boom - instant power.
And, when the piston comes back up on the exhaust stroke, there's no dome
to be pushing the exhaust off to the side - a flat-top pushes it right out
the exhaust port.

Make sense?

- Art

G'day

That's just about what I said in my earlier post...... funny how when ya been in it for a while ya all seem to end up at a similar point with a similar point of view.. ;)

The early 883 heads had a combustion chamber very similar to the new XB's .. and they were the head to have for many years..
The more things change the more they stay the same.. ;)

For street work it is VERY hard to go past flat tops and a small combustion chamber..

There's bit more to the higher compression ratios on late model sports bikes .....but that's a whole nother thread and I'm usually discussing those principles on other forums....
VERY short strokes and multiple valves work well in that instance because you are employing "tumble" instead of "swirl" for cylinder fill.



Panman IS Ron McBroom..... nuff said

Turbota

Interesting Read!!! Who is Art Northrup?? Should I know who he is???

I met Art some years ago on another forum. I think he's somehow involved with the LSR team. Maybe not but he does know his stuff.

I think I will probably be kickin your ass but who knows.If you have done more than tune your carb, then yeah, you prolly would. hehe.

Well, I talked to Justin at Nallin on the phone today. Those Hurricane "Domed" pistons are actually a reverse "Bathtub" design, and are made specifically for the 04-05 Buell heads, so that's what I'm getting. Art Northrup is correct, a traditional "Domed" piston will not work with the 04-05 heads.

A "Flat-top" piston will [not] increase the CR above the stock 9.7 to 1 since all these "Flat-tops" have a zero deck height ... Additionally, Justin recomended just getting a .015" over-bore instead of .030" ... so that way, I can still bore it another .015" if it ever needs a re-build in the future. Justin said the cylinder liners in these engines lose some structural integrity if you bore much over .030" ... so I'm not going to push it by trying to get more displacement out of these stock cylinders.

Anyway, I think the Stage 2 heads along with the 10.50 to 1 CR will wake this bike up a little.

As for the cams ... Justin likes the valve timing of the SE .551" 04-05 specific cams that are now in the motor, so he recommended that I not make anymore cam changes.

I would like more displacement, but for the extra cost of new aftermarket cylinders, I am going to just be happy with the 1200.

http://img.photobucket.com/albums/v248/Turbota/HurricanePistons.jpg

Ron,

BTW, I asked Justin if he thought I would have detonation problems with 10.5 to 1 CR. He has not had problems with other motors in the past, and the SE ignition module I am using also decreases timing 5 degrees at wide open throttle (WOT) which helps a lot.

Turboto. Over the weekend, I installed NRHS stage 2 heads. I had them mill .015 off. I was looking for 10:2 cr. I also have the "E" cams and Twin tec tc88a ignition. I haven't noticed a loss of low end torque, and, it doesn't lug in 5th gear at 40-45 mph. Still playing with the advance, currently set at 5&7. Haven't made any carb adjustments yet. I don't have a tach but the engine really comes alive around 4000-4200. Have the rev limiter set at 6600. One thing you might need to do, is grind the inner rocker boxes( I had to) where they hit the larger valve springs. That was time comsuming. Good luck with your project.

Stevo, that is pretty much what I thought, (quench/squish area) but you explained and clarified it well. Thanks

seajay ...

Thanks for the heads up on grinding the lower rocker box assembly. I am suprised someone at NRHS did not tell you about this. Certainly they have installed many of there Stage 2 heads on late model Sportys themselves.

Was it a part of the springs themselves or the retainers on top of the springs that was hitting something on the lower rocker box?

Just wondering ... Has anyone else on this forum ever used these NRHS/Hurricane "bathtub" style 10.5 :1 CR style pistons in a 04-05 Sporty yet?

Turbota. I asked Justin before I sent out the heads. He did say the rocker box/springs could be a issue. Mock up the rocker snug to head without the metal gasket, and try to fit/move a piece of paper between the top of the spring and the entire rocker box. If there is no clearence, scribe the rocker box with a small knife and and get the old dremel out. Try to cover the rockers to keep the filings away. Maybe you'll be lucky and not have a clearence problem.

Thanks Jay ...

Seajay, Have you dyno'd your bike with all those mods?

Not yet Barry. Maybe next week after I change the oil. Barry, I know you are trying different things for more low end torque and I hope you accomplish your goal. I rode my buddy's 111ci Texas Chopper last weekend. That beast had tons of torque at 2500 rpm. My bike to his is like a small block to big block. Just an observation.

Whats this TC88A ignition I keep hearing about. I haven,'t be able to get an answer from anyone but it looks like Seajay using one as well. What the deal ????

Here's the link. It's an adjustable ignition for the 04-05 sportys.


Twin Tech TC88A (http://www.daytona-twintec.com/TC88A.html)

Art is the engine guy behind a few of Crims records...He knows his shit.... George will correct me if I'm wrong on this but I'm pretty sure a few were done with Arts engine and he can fill ya's in on which records were which.

I think he's the other guy in Crims avatar...Unfortunately I havn't had the pleasure of sittin down a discussin engines over a few beers with him so I don't know.

Stevo's right. Art is the handsome guy with the gray beard in my avatar. He's pretty knowledgeable, usually has his facts right, can't argue with him. Just keep him away from the wrenches. Strange combination. Very unusual and generous guy.

He basically called Zippers and said 'build me a BIG honkin' motor. And that, they did.

And Stevo, if you sat down with Art for a few beers, you'd be there for a few days and your ears would fall off.
:yikes :yikes :yikes

I think I would enjoy that...

The reason I got on the net in the first place is to try and find guys that knew more than me.....

I ENJOY learnin and being shown a better way to do things.........

I gotta get myself stateside again..... I think I have a LOT of beer to drink ;)

Justin at Nallin just called me. Something interesting:

He wanted to tell me that he wants to use a traditional "Thunderstorm" style domed piston in my engine instead of the reverse "Bathtub" style domed piston that is normally used with the 04-05 Buell/1200 XL heads. He will need to recontour the heads with the CNC machine to make this piston and combustion chamber work togather.

NRHS said they have made more HP using the Thunderstorm style domed piston and Thunderstorm style combustion chamber in the Buell XB heads vs the stock Buell XB "Bathtub" head chamber and the "Bathtub" style dome Hurricane pistons.

He just wanted to let me know that this is what they want to do to my heads.

So, I guess what I will get is a traditional Thunderstorm 10.5 to 1 CR domed piston and a traditional Thunderstorm combustion chamber in a set of ported Buell XB heads.

Hey, it may be the best combination of the two ...

He said I would not have any piston to valve clearance problems using the 04-05 specific 249/249 .551"/.551" SE cams.

I stated once that NRHS fits the piston to bore clearance to .005"
I was wrong; There Hurricane forged pistons are clearanced to .003" (3 thousands)

Ron,

Yep, thats what Im using on our build. 10.5:1 T storm dome pistons with my XB/1200r heads. Best way to go. Make sure you dump those crappy 7mm valvestems too, you want the 10mm(7/16)valvestems.

Turbota, the T-storm piston has a 15 degree angled dome. This unshrouds the valve somewhat and also directs the fuel coming out of the squish band more directly at the flame front. It makes a more efficient chamber than a pair of flat squish bands like the stock XB/04 XL1200 head.

Even better on both counts is a 30 degree dome angle. it approximates the valve angle and gives the most direct shot at the flame front, as well as removing as much of the valve shrouding as possible. However, for a given dome height, it gives less squish area. We like to do 30 degree chambers when we start getting up over 11:1, that way we can put enough dome into it to recover the squish area and chamber turbulence. But for street use, the 15 degree angle is about ideal.

The problem with the Thunderstorm head is the squish band is cast into it, and it's rough. Doesn't line up nicely with the dome, it'll be off center, deeper on one side, etc. We can machine them but we generally have to remove at least .035 from the deck to do it, often more. I'm not a huge fan of excessive deck milling, it causes a whole range of issues. Even when you get it done, there's not a lot of surface are left because the squish band is so narrow, it can only accomodate about .120 of dome or so, any taller dome and it protrudes right past it. This is one of the things I like so much about the XB/04 XL1200 head. There's lots of material to work with, I can do the chamber exactly how I want it.

I realize that the trend in performance motors is more and more toward shallow, compact chambers with flat tops, but those motors also generally have 15-20 degree valve angles (which you can do with 4 valves per cylinder because the valves are smaller). HD's are 27 and 31 degrees, which makes for a deeper chamber. At the dome heights we're talking about, we're a long way from obstructing overlap flow. We're actually enhancing flow on both sides by angling the squish bands.

We offer the rectangular dome for the stock chamber, too, and it works and it's a nice piston. People buy it because it's a bolt-on, no chamber work required. But sticking a dome up into the middle of a chamber like that is not the optimum arrangement. As the fuel squeezes out of the squish band, it hits that dome and has to go over it. That tries to separate the air and fuel and taxes the octane of the fuel. So when we sell a kit or fit a set of pistons for someone, if we also have their heads in house, we just put them in an angled domed piston and cut their chamber for nothing. I'd rather see them have the best setup and it's no big deal for me to cut the chamber, we do it in the CNC machine.

Oh, on the valves, Nightboy makes a good point. I've heard of more than one person snapping them when they pushed'em too far. With the stock cams and rev limiter, they're fine, and even with the "E" grind they're fine, that grind has very gentle valvetrain dynamics. Hell, look at the XB9, it has "E" cams with 7mm valves and they have a 7500rpm limit on it and they work great.

But more brutal grinds take more spring pressure to control the valvetrain, and when a person is doing that, we like to go to the 5/16 stems.

We also offer a stainless version of the stock valves with the 7mm stem. It's quite a bit better piece than the factory valve and I've never had one fail. Whenever we sell stock XB heads to someone (and we sell quite a few stock heads believe it or not), we put these in it instead of the factory pieces. I can actually buy them cheaper than I get the factory valves so it makes sense.

We mostly sell XB or 04 XL1200 heads to guys with 883's. Fact is, right out of the box they work comparable to a Stage 2 883 head, and a set costs less than a Stage 2 job. Hence we don't port many 883 heads anymore. The factory only sells the new heads disassembled, so we sell them fully assembled, deck trued, breather holes drilled and tapped, high flow stainless valves, spring heights set, and we sell them for the same price as they'd cost you from HD if you went and bought all the individual pieces. Like I said, we'll also cut the chamber for them for nothing if they're getting a set of our pistons.

To add to what Aaron just said...

My 1200S heads have been welded up and machined to match the angle of the Buell pistons I was runnin....for the same reasons...unfortunately I don't have the resources or volume over here to play with as many Nallins are :( .. just interesting to see a similar path from 2 different sides of the world :)

eventually I'll get this 88" together ....

aswracing ...

Welcome to the board. I hope you find a little time to help us with tech issues.

Nice to have you as a vendor :)

Ron,