im looking to get the 1250 kit from you guys, but im wondering about compression, do you have any other compression besides 10.5:1? whats the most you can run with pump gas? i plan on getting ported heads eventually as well...

No worries, mate (damn Aussies anyway, it's catching ;) ). It's easy to move that number up to about a point in either direction without changing any components of the kit, just making little changes to the chamber. If you want to move it more than that, we generally do something different with the piston.

We chose 10.5:1 just because that's a popular place to be, assembled properly and using typical street performance cams it gives good power and generally runs fine on pump gas. Some people push it a little higher with more aggressive cams and some folks run it down a little, but most just go with 10.5:1.

Take a look at the intake close event on the cams you're considering using, that has a huge effect on effective compression. The bigger that number, the more compression you can (and should) safely run.

Thanks for the inquiry and best of luck on your project.

I am confused about the relationship between the cam and the compression. I have n8's with 490 lift and longer than stock druation. How does that affect comp. Could my cams actually reduce the compression I have. I have milled heads .050 and .027 headgaskets on my 93 1200. Please explain the relationship. Thanks

I am confused about the relationship between the cam and the compression. I have n8's with 490 lift and longer than stock druation. How does that affect comp. Could my cams actually reduce the compression I have. I have milled heads .050 and .027 headgaskets on my 93 1200. Please explain the relationship. Thanks
Hey Ralph, Think about it this way...on the compression stroke, as the piston is coming up to the top of the cylinder, the longer the intake valve stays open the more it reduces the effective compression...don't know if that makes any sense or not...I'm not the best at explaining things sometimes. :rolleyes: Not sure about the specs on the n8s, but to answer your question cams can actually reduce (or increase for that matter) the effective compression...in my engine for example I run 10:1 reverse dome pistons, but due to the timing of the cams, it lowers to below 10:1...

so, why would anyone want a long duration cam? I thought the longer duration cam would yield more power. I might have to change cams. I thought the longer the valve is open the more fill and more comp.

Hey Rottenralph...........shouldn't you be asking HDlite such important technical questions................:laugh :laugh

Hey Rottenralph...........shouldn't you be asking HDlite such important technical questions................:laugh :laugh :p :p :p :p :p :p :p :p

I was gonna ask him if nobody else answers. Maybe I can get 170 with the right cams.

I was gonna ask him if nobody else answers. Maybe I can get 170 with the right cams.

:laugh :clap :smiliesig :lmaorof :rolllaugh :lolsign

Ralph

All things being equal (which of course they never are ;) )

general cam guide ...

The more duration the higher in the rev range the cam comes on....

The less duration the earlier the torque peak occurs...

The later the intake close the more static compression you can and need to run...

A late closing inlet is usually coupled with a longer duration for better cylinder fill at higher RPM's

An early closing inlet and short duration tends fill better at low RPM's and run out of puff up top...

For a given spec
if you increase the lift ..you increase the torque as you are increaseing the area under the curve and can fill the cylinder better....

if you increase duration you tend to lose torque down low and move it further up the rev range.

Stevo is right of course, but let me add just a little.

Duration is just a "quick reference" figure to give you a rough idea of how much cam it is. All it really tells you is the number of crankshaft degrees between the point where the intake valve crosses. .053 lift while opening and again crosses .053 lift while closing. So it tells you how long it's open. But it doesn't tell you when it opened and closed, and that's actually very critical information.

The timing figures are referenced to the stroke of interest i.e. the intake timing tells you the open and close points relative to the intake stroke, and the exhaust timing tells you the open and close points relative to the exhaust stroke. For example, if a cam opens the intake valve at 32 degrees (like the N8 does), that means it opens it 32 degrees before the intake stroke begins, or 32 degrees before the intake stroke's top dead center point (BTDC). Likewise if the intake close point is 44 degrees, that means 44 degrees after the intake stroke ends, or 44 degrees after bottom dead center (ABDC).

Since the duration of the intake stroke itself is 180 degrees, this cam has 32 degrees of duration BTDC, plus the 180 degrees of the intake stroke, plus 44 more degrees of duration ABDC, equals 256 degrees of intake duration. So you see, the timing figures tell you the duration, but they also give you a whole lot more information because instead of just telling you how long the valve is open they also tell you when the valve is open. And that's critical information!

As it relates to compression, the intake close timing is particularly critical. Basically what's happening is that the motor has completed it's intake stroke, and started it's compression stroke, but we still have the valve hanging open. We don't actually start compressing the charge until we close that valve! So if you're closing it later, it stands to reason that you can run a higher compression ratio, because you're using less of the compression stroke to actually compress the charge. Likewise if you're closing the valve early you may want to run a lower compression ratio to avoid pinging because you're using more of the compression stroke to compress the charge. Hence the intake close point and the compression ratio you want to choose go hand in hand.

The reason closing the intake valve later can help is that the incoming fuel has inertia, and the cylinder is still filling even though the piston is coming up. If we close the valve too early, we slam the door while fuel is still coming in, and that hurts power. Likewise if we slam the door too late, we push some of the intake charge back out and that hurts power. You have to choose very wisely when to quit trying to fill the cylinder and instead start compressing the charge. Well, as you can imagine, the best spot to close the door depends heavily on the rpm of the engine. Part of this is because the velocity of the intake charge changes with rpm, and a big part of it is that a crankshaft degree is a different amount of time depending on the rpm. So we select an intake close point largely depending on the rpm where we care most about cylinder fill.

The intake close event is actually the single most critical cam spec as it relates to the rpm range of the cams. It's always what you should look at first when you're trying to decide whether the cams you're looking at will put the power where you want it.

Typical street cams are in the mid 40's range for intake close event. In the 50's is the hotter street cams and some of the race cams. In the 60's you find the race cams, some even get into the 70's. Below 40 degrees is where you find the high torque/stock compression type street cams.

The other cam timing events (intake open/exhaust close, aka overlap, and exhaust open) are interesting to discuss as well, and start really getting into effects of the exhaust system, but another day. The intake close is the real important event you should always look at first.

I run Red Shift 585's in my M2, they have a 59 degree intake close event, and I run 11:1 because 59 is fairly late for a street grind. So it's a bit more radical setup than most people go with. But it also yields impressive results, 124rwhp on 1250cc with a pretty broad powerband.

My Bonneville motors run intake close points of 64 degrees to 70 degrees, with CR's of 13:1 and up, and are tuned for top end power, not a broad powerband.

So, do you guys also grind cams. I have the original set and can send them out for the power upgrade I think I need. I thought the cams I have are the ones I need. I have milled heads with 9-1 stock 30 over pistons. I have no idea what my compression ratio is. Can I put these cams(red shift 585) in and expect to get a good overall gain or should I just not bother. I know the comp ratio is important for the choice but I simply don't know and don't want to pull my fresh rebuild apart to find out.

One other question. I saw that you guys make a stronger ignition rotor(WELDED AND NOT STAMPED). I have broken three rotors since the cam change. Will your heavy duty rotor fix this annoying problem or do I have to mess with the cam endplay some more. Is this problem common with beefed up motors. Iassume yes or you would not have made them.

That's a good explanation Aaron.....

I find this amusing that i'm the one giving the quick and dirty version and somone else is giving the expanded one...makes a pleasant change for me....

Another thing to note guys...is that camshaft selection is the most critical decision you can make as far as the personality of your engine...as said the intake close will largely determine how much static compression you can and where the power delivery is likely to come on.....to go expanding any further, we could quite literally type for hours and still only scratch the surface of camshaft design and then you have to bring in ignition and exhaust system design to optimise the chosen camshaft/head combo..

That's the FUN stuff, when it gets interesting....:D .. for those of us that are a bit strange anyway ;)

Ralph, absolutely we're a Red Shift dealer and can handle it for you. But I sure wouldn't use a set of 585's with 9:1 compression. It's really a grind that's made for 10.5:1 minimum. With 9:1 or thereabouts, the only Red Shift I'd consider is the 630/585. It closes the intake valve at 41 degrees, which will work with 9:1.

BUT ... none of these Red Shift grinds are bolt-ins ... i.e. they require that the heads be set up for them in terms of retainer to guide and coil bind clearance, and they need more seat pressure on the springs than the factory springs provide. Plus you've got to do some cam box clearancing (easy) to get them in, plus you've got to provide more tappet anti-rotation pin clearance (mill the flat on the side of the tappet down farther or get some performance tappets like JIMS that have a longer flat). Plus you've got to make sure you've got valve to valve and valve to piston clearance.

The other thing, too, is that to take advantage of the extra lift of these cams, you really need ports that have been reworked. Stock ports on any of the heads are totally done at .500 of lift, the small valve heads are done by .400. Lifting the valve to .630 like the 630/585 does won't buy you anything with a stock port.

I'm more than happy to sell you stuff and help in any way I can, but you need to understand this, putting in something like a Red Shift and getting it to work takes some doin'. But the results can be impressive. Bolt-in cams with stock heads leaves a lot on the table.

s sounds like my next winter project. I have started a project like this in April before and june came before I was riding. I am gonna guess that reworking my current heads is out of the question. They have been milled .050 and the ports have been cleaned up(all the lumds smoothed). I have titanium valves(bought in Germany and I think this is true) with triple valve springs and a 5 angle grind job. The intake is portmatched to my s&s manifold. Adjustable pusjrods as well. I suppose a base line needs to be established so I will go to the dyno before I do anything else.

First question, what heads should I start looking for to have modified?

Second question, are my current heads worth modding. IE bathtub chamber to increase compression. Clean up ports more.

Third, still need an answer on the ignition pickup? I have a crane hi4 if that matters.

How do I get the special stuff done if you are out west? I am handy with tools but not hot on using the dremel on the engine parts.

Would it be easier to pull the engine out and send it to you this winter so I can just put it back in with the engine almost ready to go?

Will $2000 get the job done? Will have to start budgeting for this one.

First question, what heads should I start looking for to have modified?


We can make a much better head out of an 04 XL1200 or XB head than we can out of a 91-03 XL1200 head. Or step up to a set of STD's and we can make a killer set of heads ;)


Second question, are my current heads worth modding. IE bathtub chamber to increase compression. Clean up ports more.


With enough money and effort, you can make a road racer out of a coffee table. But I'd sure rather work with a good casting to begin with. You'll be better off.


Third, still need an answer on the ignition pickup? I have a crane hi4 if that matters.


Oops ... yes, we developed that piece because the stock stamped cup is failure prone. We've never had a failure with one. It's not welded, it's billet steel.


How do I get the special stuff done if you are out west? I am handy with tools but not hot on using the dremel on the engine parts.


The cam box clearancing is pretty straightforward. On the lifters, I'd recommend some good Hydrosolids anyway, and they won't need the clearance cut. Unless you get real crazy on the cams, the valves will likely clear the pistons, our pistons have big pockets for just that reason.


Would it be easier to pull the engine out and send it to you this winter so I can just put it back in with the engine almost ready to go?


Certainly an option and lots of people go that way.


Will $2000 get the job done? Will have to start budgeting for this one.

Depends on what you want exactly. Best bet is to call the shop: (303) 833-4500. Talk to Justin, he's really good at laying out all the options for you and finding the best match to your goals within your budget. Don't worry about using up his time, that's what he does is talk to people about their projects, no obligation.

Thanks, I will have to start budgeting and deciding what I really want. I know 100 h.p. is a good starting point. I am going to go to the dyno and see what I have first in a couple of weeks. Last time was 95 and I had a whopping 72/71. Not bad for an amateur but I believe I have reached my limit and it is time to try another direction. Stroker is also an option but that is serious money and that also has to be budgeted. I will now have to think and start hiding some money from the wifee.