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cams for GS 1000

  • Thread starter Thread starter 48woody
  • Start date Start date
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48woody

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Any suggestion for cams for 78 GS1000. Will have 1085/1100 kit, 1980 GS1000G head (reworked). Want to improve LOW and MID range power, not so much high end. Cams from any other bike work? Most cams I've seen improve Mid and High end. Thanks for any info
 
48woody said:
Any suggestion for cams for 78 GS1000. Will have 1085/1100 kit, 1980 GS1000G head (reworked). Want to improve LOW and MID range power, not so much high end. Cams from any other bike work? Most cams I've seen improve Mid and High end. Thanks for any info
Click to expand...

GS850 '82 -'84 are supposed to have good bottom end and mid range response because they open the inlets 10 degs earlier.
I have the stock '79 cams in my 850 which are great from 3000 - 10,000 rpm, even with stock VM carbs. They are degreed at 110. The higher CR helps too.
 
48woody,

I went with a Andrews s1 set of cams and have never regretted it for my GS1000/1085. The s1 is only a couple of increments over stock and enhances the bottom end and mid range for better roll on performance. IMO a great street cam with over 40K miles on em to date
 
I have heard that the 1100GK cams are a good upgrade. Anyone know what the numbers are on them?
 
renobruce said:
I have heard that the 1100GK cams are a good upgrade. Anyone know what the numbers are on them?
Click to expand...
No idea on that, but ive also read the GK HEAD is highly prized by the 1000E tuners, because of the "D" shaped ports...
 
doesnt' the GS1100G head have a bigger combustion chamber? So wouldnt that be lower compression? or am I mistaken.
 
thanks all for the info, putting all the info I can into a file for when I do an engine rebuild this winter. There are a lot of things one can do to these motors it seems, just time and money.
 
This is from the 850 manual and shows changes in the valve timing when the GT came out. Which is better for torque?

valvetiming.jpg
 
What you want for your needs is cams with very little or no increase in duration but as much extra lift as possible. For My GS1k I had Webcam grind me up a special grind # 151i.

They have only 5 degrees more duration but .050" more lift. My riding impression is more power ever where in the rev range. Set your cam timing at 106 lob centers. Dan
 
Nessism said:
This is from the 850 manual and shows changes in the valve timing when the GT came out. Which is better for torque?

valvetiming.jpg
Click to expand...

My answer is it's the G model :p. It's a good question but it does not account for the other factors which might affect torque like the carb model change (Full factorial DOE would be conclusive while varying one factor (cam timing) while holding the others constant is inconclusive). The 79 GN model was VM carb equipped while the 80 GT came with CV carb and wasn't the cylinder port head opened up as well?

So Formula for Cam C/L numbers: Take timing figures, subtract smaller from larger, divide by 2 and add 90.

----------Intake--------- Exhaust

GN---------110------------ 110

GT-------- 100------------ 110

On the surface it appears the GT would be torquier than the GN but I would guess the Suzuki Engineers merely tweaked the cam timing so the 1980 CV version matched the 1979 VM model's performance. I Believe there was no significant performance change between the 79's & 80's version. Anyone have the period tests?
 
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renobruce said:
I have heard that the 1100GK cams are a good upgrade. Anyone know what the numbers are on them?
Click to expand...

Camshaft part numbers suggest the cam between the 850/1000/1100 are the same other than a change to a larger sprocket bolt.
 
Dan Ruddock said:
What you want for your needs is cams with very little or no increase in duration but as much extra lift as possible. For My GS1k I had Webcam grind me up a special grind # 151i.

They have only 5 degrees more duration but .050" more lift. My riding impression is more power ever where in the rev range. Set your cam timing at 106 lob centers. Dan
Click to expand...

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.
 
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49er said:
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.
Click to expand...

Remind me to show you my spare head when you come up :D
 
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
 
49er said:
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.
Click to expand...
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
 
Dan Ruddock said:
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
Click to expand...

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 said:
You've already got more HP than you know what to do with.
Click to expand...

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;)
 
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