I thought I would post this to document my conclusions for improving the performance of my GS1100ED head. I asked around and got input from some knowledgeable people here on the board and thought I would summarize my finding and conclusion below. This might be helpful to anyone going through their engine and trying to decide how to spend their money.
I have a GS1100ED with most of the common/popular street modifications. A GS1100ED that you want to drive on the street, but hop it up nicely but stay very street able without compromising reliability.
I'm trying to achieve a performance level above a stock 1150 (GS1100E is 109hp (80-82) 111 (83) hp and GS1150 124 hp stock) say 130-135 hp.
My configuration is 1166 kit, 0.340 webcams, 1150 36mm CV with Stage III, Accel coils, Yoshi 4:1 race pipe, APE springs, APE clutch hub, HP gears/oil pump, top end oiler. I will probably also put on 36 mm (slingshot) CV Flatslides.
As it turns out the 16V heads are very sensitive to valve seat configuration and can make much better flow numbers (and therefore more hp) with some minor machine work. In fact duing the early 80's engineers recognized that minor variations within the factory production tolerances in head work were resulting in observable differences in ET's on otherwise identical stock GS1100E's motors. So a nice balance without going to far, and killing gas mileage too much is:
A.) is to do go 1mm oversize on the intake to 28mm (same as the stock 1150 valves)
B.) If stock valves (1100/1150 23 mm exhaust and 28mm 1150 intake) then get them backcut or buy new stainless steel valves that don't need back cutting.
C.) Get a modern radius cut valve job on your seats using a Serdi
http://www.aperaceparts.com/headwork.html
D.) Minor clean up porting to smooth the area where the seat were opened up for the 28mm valves.
Ray's quote....
and more from Terry.....
This will flow about 90-95 cfm v.s. stock 75-78 cfm if I remember my numbers correctly. So you are basically getting the equivalent of stock Gixxer 1100 head performance with your GS1100 head.
Then depending upon the 36mm CV or 36mm Slingshot carbs, the combo above is conservatively between 130-140 hp (v.s. 111 stock), and will be easily capable of having your front wheel off the ground. You will be in the mid 10's quarter mile v.s. mid 11 stock.
Any U guys want to correct my number please let me know. But this is basically the upshot of asking alot of questions from some guys that know. My preference is to take the a low mileage stock head with stock GS1150 intake , stock exhaust ; back cut them as these are all Suzuki parts.
If you go bigger than this on the head, then you will need some really large jets and are starting to get into the 38 mm regime for carbs. Ask Chef he is at 1.5 mm oversize on intake and minor porting. He is a big guy and needs the extra horses. If you are under 220 lbs, then 135 hp is going to fly. Start thinking about suspension upgrades will all that hp as well.
Pos
P.S this is 1100 16V stuff, but probably still applies in general (as to head work) to other 16V and 8V motors.
EDIT Here are Some Summary from numbers comapring a Stock head, to two other proted heads. Mine has 1150 28/23mm backcut valves and Nick's is ported a little more aggressive but with stock 27/23mm backcut valves
I have a GS1100ED with most of the common/popular street modifications. A GS1100ED that you want to drive on the street, but hop it up nicely but stay very street able without compromising reliability.
I'm trying to achieve a performance level above a stock 1150 (GS1100E is 109hp (80-82) 111 (83) hp and GS1150 124 hp stock) say 130-135 hp.
My configuration is 1166 kit, 0.340 webcams, 1150 36mm CV with Stage III, Accel coils, Yoshi 4:1 race pipe, APE springs, APE clutch hub, HP gears/oil pump, top end oiler. I will probably also put on 36 mm (slingshot) CV Flatslides.
As it turns out the 16V heads are very sensitive to valve seat configuration and can make much better flow numbers (and therefore more hp) with some minor machine work. In fact duing the early 80's engineers recognized that minor variations within the factory production tolerances in head work were resulting in observable differences in ET's on otherwise identical stock GS1100E's motors. So a nice balance without going to far, and killing gas mileage too much is:
A.) is to do go 1mm oversize on the intake to 28mm (same as the stock 1150 valves)
B.) If stock valves (1100/1150 23 mm exhaust and 28mm 1150 intake) then get them backcut or buy new stainless steel valves that don't need back cutting.
C.) Get a modern radius cut valve job on your seats using a Serdi
http://www.aperaceparts.com/headwork.html
D.) Minor clean up porting to smooth the area where the seat were opened up for the 28mm valves.
Ray's quote....
and more from Terry.....
headsbikesmopars said:
This will flow about 90-95 cfm v.s. stock 75-78 cfm if I remember my numbers correctly. So you are basically getting the equivalent of stock Gixxer 1100 head performance with your GS1100 head.
Then depending upon the 36mm CV or 36mm Slingshot carbs, the combo above is conservatively between 130-140 hp (v.s. 111 stock), and will be easily capable of having your front wheel off the ground. You will be in the mid 10's quarter mile v.s. mid 11 stock.
Any U guys want to correct my number please let me know. But this is basically the upshot of asking alot of questions from some guys that know. My preference is to take the a low mileage stock head with stock GS1150 intake , stock exhaust ; back cut them as these are all Suzuki parts.
If you go bigger than this on the head, then you will need some really large jets and are starting to get into the 38 mm regime for carbs. Ask Chef he is at 1.5 mm oversize on intake and minor porting. He is a big guy and needs the extra horses. If you are under 220 lbs, then 135 hp is going to fly. Start thinking about suspension upgrades will all that hp as well.
Pos
P.S this is 1100 16V stuff, but probably still applies in general (as to head work) to other 16V and 8V motors.
EDIT Here are Some Summary from numbers comapring a Stock head, to two other proted heads. Mine has 1150 28/23mm backcut valves and Nick's is ported a little more aggressive but with stock 27/23mm backcut valves
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I want to be safe at twice the posted speed but not 3 times posted speed 
. Get your Hayabusa out if you need that. 
.
