Valve Timing GS1150

[Flo]

Hi,

After reading Greg Cope's recomendations on APE's website and looking through the Megacycle Cam catalog, the Suzuki Manual I did this:

IO 9 BTDC
IC 48 ABDC
dur@1mm 237 (measured by me)
LCI 109,5

EO 44 BBDC
EC 5 ATDC
DUR@1mm 229 (measured by me)
LCE 109

stock GS1150 cams, all cam events at 1mm lift.

GS 1150 bored to 1327, larger intake (28.5) and exhaust (23 I think, cannot remember right now out of head) valves. 4-1 with open muffler, will get 36mm flatslides.

Any comments? Except going for a larger cam (maybe next season)

Regards
Flo

[trippivot]

you have some tunning numbers. OK you have 14 degrees overlap

what is the plan for this engine torque or horsepower?

[rapidray]

With stock 1150 cams I would set them up at 106 on the intake & 108 on the exhaust. On the dyno we just don't find good power setting the stock cams up above those numbers. Like 5-10 hp LESS! I would definitely go with G4 or G8 cams in a 1327 at LEAST! Ray.

[cbxchris]

With stock 1150 cams I would set them up at 106 on the intake & 108 on the exhaust. On the dyno we just don't find good power setting the stock cams up above those numbers. Like 5-10 hp LESS! I would definitely go with G4 or G8 cams in a 1327 at LEAST! Ray.

I'd agree with that. With most after market cams somewhere around 110 is a good place to start.

You had better make sure your valve pockets are acceptable to larger cam especially if you are running over size intake valves. Long adjuster screws in the rockers might be nice too.

[blowerbike]

for some reason he only has .5mm over size intakes..
if he had bent intakes and no stock ones was available and/or the machine shop didnt want to look around for used 1150 intakes..
maybe thats the answer why only a .5mm bigger set of valves.
stock is 28, the 1150 seats can hold a 29.5mm.
at 29.5mm thats alot of hogging out and can get a little expensive but make alot of horsepower.
1150's share the same size exhaust as the 1100's @ 23mm.

[rapidray]

This is why I build a lot of GSs with GSXR heads! You can go 30/26 valves on stock seats with only a valve job! Ray.

[Flo]

the goal for this motor is as much torque as possible, a 10hpp loss on top does not matter, should be lpenty left. More cam is an option for next season. Want to get it running now and see what it does. I think I will have plenty to upgrade on my driving skills before running out of motor!

The reason for the "small" intake valves was that I originally wanted to upgrade a GS1100 motor... then scored an 1150 but already had the parts.

Valve pockets DO accept more cam!

Ray, now you make me think again. May have to look it over. I was wondering why the Cope recomendations were so conservative. Compared to the setting s of the mildest aftermarket cams.

[rapidray]

Also, if TORQUE is your goal, set them at 104 & 106. Ray.

[trippivot]

more homework necessary

a wise person will have the head flowed on a flow bench THEN match a camshaft grind (lift, duration) to the head flow test data results.


the valve pocket can handle 2" of cam lift if the cam timing numbers are set right.

I suggest getting it together "stock " gaining the skill set to operate this machine at 9-10ths potential Before trying to re-invent an already well balanced power plant..

stock engine and transmission utilizing ONLY final drive gear ratio alterations will be the cheapest and easiest way to manipulate power/torque peaks for any specific application.

[Flo]

got 24mm exhaust actually, loooked it up.
Have the cams at 105 and 107 now. Will stay like that util it runs.

Very interested in baseline for setting the ignition. Got 12.5 to 1 compression. Will run 100 Octane gas.

[blowerbike]

got 24mm exhaust actually, loooked it up.
Have the cams at 105 and 107 now. Will stay like that util it runs.

Very interested in baseline for setting the ignition. Got 12.5 to 1 compression. Will run 100 Octane gas.

your saying the machine shop installed 24mm exhaust in the head for you?
105/107 is fine.

[Flo]

correct, got 24mm ex valves and 28.5 in.

[rapidray]

the valve pocket can handle 2" of cam lift if the cam timing numbers are set right.

Yes, but the ROCKER ARMS can't!!! Ray.

[rapidray]

got 24mm exhaust actually, loooked it up.
Have the cams at 105 and 107 now. Will stay like that util it runs.

Very interested in baseline for setting the ignition. Got 12.5 to 1 compression. Will run 100 Octane gas.

If you have 100 octane I would consider that the MINIMUM octane for 12.5 to 1! If you go to 108 octane you can put 36 degrees of timing to it & make even MORE torque! With only 100 I would max the timing at 32 or 33 to see if it handles it ok. DETONATION is deadly!!! The biggest key to this will be how you FINISH prep the piston domes & the combustion chambers. Ray.

[trippivot]

Yes, but the ROCKER ARMS can't!!! Ray.

yeah you are right. my point was not literal.

the valve timing I usually tend to use is never the same from engine to engine. * milled head surface *valve sizes *combustion chamber height * intended power use * cam specifics .. etc.. --not that any number is right or wrong. safe and lazy or aggressive and FAST!

I like to get the valves as close to the piston crown and as close to the other valve on overlap.( lower numbers) as possible. sticking to some secret engine builders clearance numbers. keeping in mind at 10K revs everything stretches out a bit.

the numbers given by the cam manufacturers are so safe and slow

as far as ignition timing well suzukis' are fastest at 38 degrees advance-static- non changing.

both of these details cam timing and ignition timing are serious tunning factors. they can make you fast ,slow , or explode.