cams for GS 1000

[GregT]

To a certain degree you are all correct. Yes, just increasing lift alone without optimisimg the rest of the factors affecting flow should not have a big effect - nevertheless in these motors it does. Why ?
IMO principally because the ports are oversized for the rev range - and hence gas speed they are most used in. By going to more lift without more duration you produce a stronger vacuum signal in the port and use more of the port's volume.
To the question of which standard cam timing will produce more torque - well the guy who said dial them in to 106 - 106 got that right - in fact anything from 104 - 106 to 108 both will produce an improvement over stock.

Greg T

[Dan Ruddock]

Increasing lift doesn't help a lot of street engines, it depends on many variables such as port shape/size/tract length, carb type and size, exhaust systems and ignition advance curve. The trick for tractability is to increase the rate of opening and flow rates at that point of induction. This is how good torque is produced. The shape in and around the valve pockets and the lead in tract shape is crucial to achieving this.

For two cams with the same duration there are two way to increase lift. They are add more lift to the nose of the cam which creates a very sharp nose which can have wear problems or increase the rate of lift to achieve the lift with a more sane cam nose. The webcam 151i increases the rate of lift and the nose is just a little sharper than a stock cam. The one draw back of this is stronger springs are a good idea. Dan

[49er]

For two cams with the same duration there are two way to increase lift. They are add more lift to the nose of the cam which creates a very sharp nose which can have wear problems or increase the rate of lift to achieve the lift with a more sane cam nose. The webcam 151i increases the rate of lift and the nose is just a little sharper than a stock cam. The one draw back of this is stronger springs are a good idea. Dan

True. I prefer to open the valves quicker rather than increase lift too much. I do take what GregT has said above into consideration too. That's why I'm quite happy to keep running the small port head and small bore VM carb combination on the 850. The low to upper mid range torque is great when the other parameters are matched accordingly. The other drawback with high lift cams is they usually require a significant increase in valve spring tension, which reduces some of the HP gains you're trying to achieve. Cams can wear signifacantly faster too with higher lift loads, not ideal for street use.

[49er]

Remind me to show you my spare head when you come up

Lets not turn this into "Brother Love's travelling salvation show"!!!!

You've already got more HP than you know what to do with.

[Colin Green]

You've already got more HP than you know what to do with.

1/10 hp per pound is only enough to keep her upright without using the centre stand .. besides, I'm a busy guy and can't afford to waste time talking to plod on the side lines

[trippivot]

web 110 best option for street

get the web 110 grind worth 2X their weight in gold. drop right in, instant seat of the pants power increase.

cam timing numbers are not exact and vary from engine to engine even if they have the same equipment combination.

this is where there is a bit of black magic and real tuning secrets are truly kept. ( but I'll give you just a taste)

some engines will pull crazy hard with 103 int and 105 exh and other engines will pull harder with 108 int and 110 exh. These numbers are relative to a certain point depending on final drive gearing and weight of the bike and rider. You can run equal numbers on int and exh there are no set rules except for mechanical interference.(valve to valve and valve to piston) Now if you start to tune down to lobe centers like 112 and 114 numbers you will get so much more bottom end at the expense of top end revving.(higher numbers are safer to run due to lack of interference)

this is where you need to decide some limits and have a plan of what you really can/cannot live with.

[TeamDar]

Now if you start to tune down to lobe centers like 112 and 114 numbers you will get so much more bottom end at the expense of top end revving.(higher numbers are safer to run due to lack of interference)

.

You sure about that? Those are top end numbers. 103 to 105 are bottom end numbers.

[48woody]

Thanks for all the replys to this thread and all the info. I can see that when I get my motor rebuilt, hopefully by next spring, I'll be spending some time degreeing in the cams to get the best performance. everything else, larger pistons, head, etc seem fairly straight forward. The cams and carb tuning will take the fiddling with to fine tune the bike. I didn't mention originally, but have been thinking of looking for a set of 34mm flatsides for carbs.

[trippivot]

I am probably wrong. I must assume you get your information from a book- not a dyno or the drag strip.

I positively sure the lower numbers create a stronger sonic pulse that pulls air/fuel into the engine.

I am also positive I can make more power with a smaller displacement engine than most engine designers.

I want to make a statement:

theory and reality do not live in the same neighborhood. practical application of cam timing numbers are relative to the work being done.

[rapidray]

Sorry Jeff, but you ARE wrong on your lobe center numbers. You got them backwards & I AM an engine builder! I don't just play one on TV! LOL!!! Ray.

[sharpy]

No idea on that, but ive also read the GK HEAD is highly prized by the 1000E tuners, because of the "D" shaped ports...

Bloody oath!!!!!!!!!!!!!!!!! and the chambers suit the 1085 kits