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View Full Version : How to pick a 400EX cam (a specification comparison)



GPracer2500
06-11-2006, 01:25 AM
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I see a lot of questions about 400EX cams. I thought it might be helpful to have a list of many of the available cams with their specifications. I picked up these specs from various places...if anyone sees errors point them out. The Hotcams specs are straight off their website and I called them to get the specs for the old version of the stg 2.

I won't comment on brand X vs. brand Y because I'm not qualified to do so. Also, I can't really comment on how cam X will perform in your quad because in most cases I don't specifically know that information. Instead, I've tried to put together some technical information that might help YOU decide what cam might suit you and your engine.



On to the specs!!

cam: Intake lift; Exhaust lift; Intake duration; Exhaust duration

stock............... .316, .302, 234, 238

XR400.............. .326, .321, 240, 244
HRC................. .350, .339, 254, 256
GT Thunder....... .350, .345, 256, 256
WB Track.......... .350, .345, 256, 256
WB All Around.... .345, .335, 240, 248
WEB 450/451..... .350, .345, 256, 256
WEB 479........... .378, .378, 250, 250
WEB 463/9i....... .385, .370, 272, 270
Hotcams stg 1... .354, .354, 246, 246------Intake centerline 106, Exhaust centerline 107
Hotcams stg 2... .354, .350, 254, 248.5----Intake centerline 106, Exhaust centerline 104.25
HC stg 2 (old).... .348, .349, 254, 254------Intake centerline 106, Exhaust centerline 107
Hotcams stroker. .358, .354, 262, 257------Intake centerline 110.5, Exhaust centerline 104.5
Megacycle x1..... .346, .346, 246, 246
Megacycle X2..... .378, .378, 254, 254
Megacycle X6..... .402, .385, 270, 262

Notes:

--Numbers are listed in inches and degrees of crank rotation (lift duration at approximately .050" lift).
--The Hotcams stg 2 old version is identified by "HCDG NO. 08" etched onto the cam--not sure what the current version says. Hotcams part number for the old cam is 1008-2.
--Valve clearance specs for all Hotcam cams are: intake .005", exhaust .006"
--White Brothers All Around is etched with "WB1870".
--White Brothers Track is etched with "WB1498".
--Notice that the WEB 450/451, GT Thunder, and WB Track are all the same grind.
--Honda part number for the HRC cam (it's actually an XR400 HRC cam) is 14000-NKK-000. I don't [i]think they are still available from Honda.
--Some retailers list a Hotcams Stage 3. This is an sometimes an erroneous label given to the "old" version of the Stage 2. Some retailers have stock on both the "old" and "new" versions and have to call the "old" version something, I guess. Other times the "stage 3" label is given to the stroker cam. So just be careful concerning the the "stg 3" label cause it could mean different things.
--This is what Hotcams told me about the performance difference between the "old" and "new" versions: "...As far as the difference between the old stage 2, and the new stage 2, the new stage two still has a good top end gain, but doesn't loose as much on the bottom..."



The lift is how far the cam opens the valve. The duration is how long it leaves it open. The more lift and duration the more aggressive the cam. Big lift and duration numbers work best at high RPM while more mild numbers are best for lower RPM.

The more duration the intake valves have the more important it is to have a high(er) compression piston. This is because with lots of duration there is more opportunity for air to escape through the valves as the piston begins its compression stroke. Even on the stock cam, the intake valves are still open when the piston begins its compression stroke. With an aggressive cam some dynamic compression is lost through valves that stay open for a long time. This must be made up for with a higher compression piston. An aggressive cam with a stock compression piston may actually perform worse than the stock cam because too much compression is being lost through the valves being opened so much. I have personally seen this happen--dyno confirmed (although it wasn't a 400EX).

Here's a theoretical example to help in understanding this concept:

-bore: 85mm (stock)
-static compression ratio: 9.1:1 (stock)
-elevation: 1500ft
-intake valve closes: 40deg ABDC (After Bottom Dead Center) (stock at 1mm lift)

The resulting dynamic compression ratio is 8:1. Note that is a smaller figure than the static compression ratio we started with. Again, this is because the actual compression of the compression stroke doesn't really start until the intake valves close.

Now, if we increase the intake valve duration to 55deg ABDC and leave the static compression ratio at 9.1:1, we get a new dynamic compression ratio of 7.4:1! In order to get the dynamic compression ratio back to where we started (8:1) with the increased intake valve duration we would need a piston with almost 10:1 static compression. Just for the heck of it I looked at how 5500 ft of elevation changes things. At 5500ft with the 55deg ABDC spec you'd need a 10.8:1 static compression piston to yeild an 8:1 dynamic compression ratio.

Now, you might be thinking what's the point of adding a cam and a piston if doing both gets you the same dynamic compression ratio you started with?? Good question. The answer is that now you have the same dyanmic compression ratio you started with but also have the cam specs that will allow the engine to breath better. And in the real world, most piston choices are actually going to bump your dynamic compression beyond what it was stock even with the addition of a cam. A 10.5:1 piston with a cam (using the 55deg ABDC spec) would get you a dynamic compression ratio of 8.6:1--0.6 points higher than all stock.

I used a dynamic compression ratio calculator to get those figures. I guessed on certain required values because there's some information I don't have. So, the above numbers are not quantitatively exact. But the relationship between static compression, dynamic compression, and intake valve timing IS accurate.



Knowledge is HorsePower!

JOEX
06-11-2006, 11:30 PM
Thanks for consolidating this info GPracer:)

Can you elaborate a bit on Duration and Lift and how they affect performance? i.e. How a relativly higher lift/shorter duration cam performes differently than a lower lift/longer duration cam.

I'm not sure if this applies to the 400ex and similar motors though....

GPracer2500
06-12-2006, 04:18 AM
Originally posted by JOEX
Thanks for consolidating this info GPracer:)

Can you elaborate a bit on Duration and Lift and how they affect performance? i.e. How a relativly higher lift/shorter duration cam performes differently than a lower lift/longer duration cam.

I'm not sure if this applies to the 400ex and similar motors though....

I'll try and answer with my current level of understanding:

Increasing lift without increasing duration will normally yield more power throughout the RPM range. However, an increase in lift is almost always accompanied by an increase in duration.

Lift and duration generally go up and down together because of practical limits governing the shape of the lobes. If you tried to have super high lift with moderate duration than the lobes would become prohibitively "pointy"--very tall but narrow. The ramps of the lobe (ramps are the transition zones on the sides of the lobe) can only be so steep for reliable valvetrain operation.

Specific to intake valves, there is a limit to the speed of the intake charge before effiecency begins to drop off. That natural "speed limit" for the intake charge helps do define the lower limit of possible lift specifications for any given duration. Long duration with moderate lift would leave you with very high intake charge speeds. Go too fast and you start going backwards. That doesn't apply to the exhaust gases exiting the exhaust valves though. I'm not sure why.

I hope that at least partially answers your question. I'm gonna stop there because I'm starting to get in over my head--I'm no expert on these matters.

ETA: Actually, I probably should have stopped before I started...really, I'm an amature. I'd much rather we got answers from an expert.

Choppers
06-20-2006, 05:55 PM
you should sticky this. so many people ask about this.

Choppers
06-20-2006, 08:12 PM
Messed up

GPracer2500
06-26-2006, 04:47 AM
I wonder if this info is really helping the average joe make a choice. I feel like something is missing--but I'm not sure what. :ermm:

Where does valve overlap fit into this? Why don't cam manufactures publish overlap data? Is there away to evaluate the most efficient RPM (peak torque) for a camshaft from lift/duration numbers alone?

Are there any engine builders that could enlighten us?

PowerJunkie
06-28-2006, 04:07 PM
so how do you know what is the best rise heigth?

GPracer2500
06-28-2006, 05:21 PM
Originally posted by PowerJunkie
so how do you know what is the best rise heigth?

To the best of my understanding, it depends on how the rest of the engine is configured (porting, bore, compression ratio, etc.) and where you want the engine's power to be concentrated (low rpm vs. high rpm).

I realize that answer may not help you make a decision. But when I try and elaborate more than I already have in the original post, I start becoming unsure of the accuracy of my advice...

07-22-2006, 01:03 PM
do have any specs on the magnum cam

GPracer2500
07-22-2006, 01:39 PM
Originally posted by pimpin416ex
do have any specs on the magnum cam

I've looked and can't find squat. Last time I looked I couldn't even find a website for the manufacture....:ermm:

07-22-2006, 06:39 PM
ok thanx

EXevan91
07-24-2006, 11:47 AM
the magnum seens to have long duration and i meen alot. i have one and i scompared to stock and lots more duration

GPracer2500
08-20-2006, 10:35 PM
I see a lot of discussion about the HC stage 2 vs. the HC stage 1 for a stock compression engine. I've done some calculations to define how much the stage 2 might hurt bottom end performance. If you read the entire first post then you know that the issue is the loss of compression from the intake valves staying open a long(er) time. Compression is a dominating factor for producing low end torque. Here's the difference:

Taking into account the valve specifications:

Stock cam cranking compression at 1000ft = 8.2:1
HC stage 1 cranking compression at 1000ft = 7.8:1
HC stage 2 cranking compression at 1000ft = 7.6:1

If you go to a 11.0:1 piston (instead of the stock 9.1:1 piston) then the numbers change to:

stock cam: 9.9:1
HC stg 1: 9.5:1
HC stg 2: 9.2:1

(figures may not be absolute but the comparison is accurate)

kennymac131
09-02-2006, 12:37 PM
Does anyone know where to get the white bros. all around cam for a good price? I live in Mesa, AZ and I would assume that local dealers 1) would be expensive and 2) would have to order it. So I'm willing to go mail order.

Any help is appreciated.

Does anyone use this cam? What are your thoughts?

wilkin250r
09-02-2006, 09:08 PM
While extremely informative, I'm sure some people are a bit confused on what the numbers MEAN, and also what the numbers DON'T tell you.

As GPRacer said in the third post, higher lift generally means more power. The valve is actually open more, so the engine breathes better. But it's not always possible to increase lift without increasing duration.

As a general rule, more duration will have more top-end power in higher revs, but less low-end power.

wilkin250r
09-02-2006, 09:24 PM
Now let's talk about what the specs DON'T tell you.

What is duration? It's a measurement of how long (in crankshaft degrees) the valves are open. But an important aspect is the definition of "open". If the valve is lifted .001 inches (about half the thickness of a piece of paper), it's not really "open" because you don't get any meaningful amount of airflow through such a small opening. So cam manufacturers define "open" when the valve is lifted at either 1mm (about 0.040"), or 0.050". Both are standard, it just depends whether you're using a metric system or not, but they don't always tell you which one they measure to. YOU need to be aware of the issue because that difference of 0.010" can change your specs by a degree or two. You may wish to talk to the manufacturers to get all the information.

wilkin250r
09-02-2006, 09:41 PM
The specs also don't say anything about overlap, and it can be extremely important. Overlap is the amount of time (in crankshaft degrees) that both intake and exhaust valves are open.

Overlap is critical because air has mass, and therefore has inertia. It doesn't move instantly, and it doesn't stop instantly. Both are important.

When the exhaust valves open, the exhaust gasses go rushing out, and the piston begins it's upstroke. The piston gets near finishing the exhaust stroke, and the intake valves open before the exhaust valves close. Why?

You have exhaust gasses moving OUT, and they have their own inertia. Meanwhile, the air sitting in the intake also has inertia sitting still, and it takes energy and time to get that air moving. Wouldn't it be great to use the inertia of the exhaust going out to help kick-start the intake process? This is exactly what overlap does. Because both intake and exhaust are open during overlap, it takes advantage of the inertia of the exhaust gasses to pull a vacuum inside the cylinder, and that vacuum will help get the air moving inside the intake. This means that you can actually begin the filling process BEFORE the piston begins it's downstroke. This is called scavenging.

On a related note, the intake duration actually extends past BDC, because of the inertia of the incoming air. The air is already moving, and doesn't stop instantly. That can be used to stuff the cylinder even after the piston begins it's upstroke, like a super-charging effect.

Now, this stuff happens at high RPM, when air is moving the fastest and thus has the greatest momentum. But what happens if that momentum didn't exist? When the piston begins it's downward stroke, it would pull in air from both the intake AND exhaust, because the exhaust wouldn't have that outgoing momentum and would be free to reverse. Obviously the exhaust won't burn a second time, so any space it takes up is lost power. Likewise, if the intake valves are open after the piston begins it's compression stroke, you certainly wouldn't super-charge the cylinder, you would force a little bit of air OUT, back into the intake. This not only results in lost power, but it would pass through the carb again, and get mixed with more fuel and result in a double-rich mixture.

This is exactly what happens at low RPMs. Without that velocity, the air doesn't have momentum. This is why camshafts designed for high-rev have very poor performance at low RPMs and rough idle. The exact same things that are beneficial at high rpms will cause problems at low rpms.

This is also related to head porting. This is why bigger isn't always better, because the key is VELOCITY, not AMOUNT. Although a larger port might be able to flow a larger AMOUNT, it may have a lower VELOCITY, and that velocity is very important to your scavenging and supercharging effects.

GPracer2500
01-17-2007, 10:45 AM
Some info from a recent thread that I thought belonged here too:

Regarding the various Hotcams cams, there are four different cams.

A few years ago 1043-2 replaced 1008-2 as the stg 2 and the "Stroker" cam was released. Hotcams has since dropped the "Stroker" label and now calls that cam Stg 3. But sometimes the old stg 2 (1008-2) is called a stg 3. :confused: Some of the Hotcams "stage" labels are ambiguous. It's better to use the HC part numbers to possitively identify.

1007-1: Stage 1, always has been.
1008-2: The original stage 2. Sometimes called "old stg 2" and sometimes called stg 3. No longer being manufactured.
1043-2: The current stg 2. Replaced the 1008-2.
1051-3: The current stg 3. Use to be called the "Stroker" cam by Hotcams.

Got it? Good. ;)

cam: Intake lift; Exhaust lift; Intake duration; Exhaust duration

1007-1... .354, .354, 246, 246------Intake centerline 106, Exhaust centerline 107
1043-2... .354, .350, 254, 248.5----Intake centerline 106, Exhaust centerline 104.25
1008-2... .348, .349, 254, 254------Intake centerline 106, Exhaust centerline 107
1051-3... .358, .354, 262, 257------Intake centerline 110.5, Exhaust centerline 104.5

Those are the 4 Hotcams cams for the 400EX. It's no wonder some manufactures just stick with numbered names instead of "stages".

hypersnyper6947
05-31-2008, 01:01 PM
I have the 1043-2 and with my mods im wondering if i should get the old stage 2 or a stage 1. Will this work well for my 440 11:1, i already have just have not installed it yet.

tri5ron
04-06-2009, 01:20 PM
Bump.
(Just because I had not seen it up for a while).