Cam Degree Questions

I'm in the process of degreeing the cams on my Gsx-R 600 and have some questions. Engine is stock bore, Yoshimura cams, stock head gasket with .005 milled off the head surface. I have all the numbers recommended by Yosh, but I realize those numbers could vary. My question is, do you concentrate on hitting the lobe center number as long as the opening and closing numbers are close to what is recommended or should all 3 numbers match what is recommended?

Example: Yosh recommends 26* opening, 56* closing to equal 105* lobe center with at least .09mm PTV on the intake cam.

The last measurements I took before I stopped fooling with it was 22* opening, 56* closing to equal 107* lobe center with 1.2mm PTV.

What sort of range am I looking to get into? I can get within a degree either way with the lobe center but I cant get the opening and closing numbers to match up.

 

Lobe centers(for me anyway), then check PTV.
OR you could do what Pops used to do...just run the valves as close to the pistons as was safe and ignore the degree wheel.

 

You will get better acceleration if you bring the lobe centers lower, closer to the minimum PTV. 600s need midrange, get it if you can. Valve lash will affect those opening and closing numbers a bit, but don't be concerned if you don't get a match. Check the lift and duration in the process and you might get some insight into the variation you're seeing.

 

Also, if you are running at shorter tracks where acceleration is king (over top speed), you can reduce overlap by moving the exhaust rearward, while advancing the intake.
An interesting experiment is to degree the cams with a comp gauge installed in one cyl so you can crank it over on the starter (rigged up on the bench of course) and watch the cranking comp go up as you adjust the intake forward.

 

That would be beneficial if you raced them at cranking speeds....

The closer to BDC the more compression you'll have, have you a custom ground that closes at BDC and see how it runs.

I personally don't like the run it as close as you can mentality, it makes for a flat bland powerband, I prefer sumthin with a little more personality.

 

Thanks for the info guys. Couple more questions. What do you look for as far as repeatability? I feel like I'm having trouble getting the exact same numbers several times in a row. It seems like every time I rotate the engine and check the numbers, either the opening or closing number will have changed a little. Do I get the numbers as close as possible and look for consistant PTV? I'm trying to avoid any false positives. I dont want to think I've got it dialed in and find out the hard way that I missed something or I've measured wrong.

 

Beat thing u can do is put stock cams back in! You've just list hp & a lot of midrange. I got 2 sets if the 600 st yosh cams after redoing 2 for a guy & getting way better hp & tq from stock. Honestly only in 130+hp sbk's have we ever had any luck. Sell those cams to a 750 guy he'll like them. Sorry if raining on your parade but not too many folks had luck with those grinds. Also u have low compression with stock hg & only. 005" offhead. Those 600 u can set up.a lot tighter but with those yosh cams ptv will limit u.

06-07 SS gsxr600 with stock cams & good pipe tune & vp can make 124+ easily.

 

1.2 on exhaust pretty close imo for a club season long bike..again like rm says these bikes need midrange and the yosh cams KILL THAT plus due to their profiles u can't get lobe centers low enough without ptv issues the way u have it set up it won't be faster than stock imo slower off corners especially

 

I havent checked PTV on the exhaust yet. The 1.2 was on the intake. As for which cams to use, I'm just using parts that I had out of an engine that dropped a valve. I ran that engine for over a season and found out after it blew that the valve springs were shimmed wrong as well as the adjustment shims. I've fixed both of those issues with this engine. I'd like to at least make an attempt at setting these and seeing what I come up with.

 

I also avoided the high compression numbers when I rebuilt this engine to get around running race gas. I was spending over $100 a weekend just in race fuel on the previous motor and it was a total waste in my opinion. This was my first engine build and I wanted to put a solid, reliable engine back together with parts I already had and get back out on the track.

 

so you keep compression low to avoid paying for race gas but have $1,100 camshafts??

anyways, best thing you can do it sell those cams to a 750 guy and put stockers in..honestly do back to back dyno runs! ANY lobe center numbers you'll see the yosh cams on that 06-07 engine will make LESS hp everywhere but the last 3-500rpm...5-800 if you have an empro..but again you'll loose hp everywhere..trust me i spent over 14hrs on the dyno with them when we had a racer that had 2 T/H built GSXR's and they were turds..we swapped just the cams out and they came way back...then when we built them/rebuilt them for this year, we ran stock cams again in the SS and in the SBK went back to the Yosh ones (along with a LOT of other sbk parts, they were bit better, but still not hugely even in 14.8:1 sbk engine) He went on to pretty much sweep every race at Miller this year on both bikes, 0 mechanical's...im only telling you this to show we REALLY played with them, tried them in several formats, tested and found what worked the best..Sorry if harsh, id rather be a dick and honest then blow smoke up your butt.. i LOVE Yosh stuff and use it a lot, but their GSXR600 cams DO NOT work (now put them in a GSXR750sbk )

If your stuck on using them, keep the PTV on the intake over .85 and 1.4 on the exhaust at least thats safe..run the v/c on the loose side IMO with those cams .25in and .30ex..(yes yosh says run on tight side) good luck.

 

I used the trick at Henderson which was a (now defunct) track that had very little top end work but lots of corners to power out of.
We beat a pretty strong Ducati for a championship there by out pulling him out of corners on a Suz BUT it shut off like a lightswitch above 9000..so I agree it's not a good plan for anywhere that sees high rpm in top gear...

 

Long story short, bought an old AMA Formula Xtreme 600 loaded with good stuff for a crazy good price. Yosh cams and Carrillo rods were already in the motor. Whoever had been working on the motor put shims under the valve springs 1mm too thick and it eventually popped the tip off one of the valves and it dropped ruining the motor. I just installed the Yosh cams because I had them and thought I could tune for them. Never used them before.

Any input is appreciated. I want to get it right so I can race.

 

Josh - it should not change if you have a stable platform for your indicator and a good point. Most builders braze a long custom welding rod to a standard indicator point to get the indicator up away from the cams or add curves or grind it thinner. If you are trying to achieve a PTV that is close to absolute minimum, you should check all the valves or at least more than one.

 

Thanks Rick. I took a second look and I think the thin walled metal I used when I welded up the engine stand is flexing a little when I turn the engine over, causing a little bit of a diving board effect on both the engine and the dial mount. I'm going to change my mount and put a couple of pieces of wood under the tip of the oil pan to minimize any movement.

 

GSXR? lay it on the bench tilted off the pan and resting on the front mount. Very stable.

 

That is a great story.. but I do not believe it.. Running too much shim under the valve springs can cause coil bind, which would first wipe the cam(s) out big time... and you should feel it binding when turning the engine over by hand...

Ron

 

Yoshimura's install instructions says install a .5 mm seat shim on the intake side and a .3 mm seat shim on the exhaust side. One of the seat shims that I took out of the head after the valve dropped was 1.5 mm. The valve that dropped broke right under the retainer, about 3/8 inch below the tip of the valve. I still have all the pieces including the 16 shims that were over 1mm too thick and the broken valve tip I pulled out of the retainer if you would like to inspect them yourself. I raced the bike for well over a season just like that and it ran just fine until it dropped the valve. I dropped and disassembled the entire engine and measured the shims personally. The cams are just fine and the numbers on the shims dont lie.

The shims were way out of spec. Whether that was the direct cause of the valve dropping, no one will really ever know. The valve just dropped. I dont think its a coincidence that the springs were under that kind of pressure and then a valve breaks. The pressure has to go somewhere, and its certainly not going to pull the big end of the valve through the head, so its no suprise the little tip snapped off. You shouldn't question a person's credibility in regards to a bike you've never raced and an engine you've never serviced or inspected.

 

FWIW, the spring seats and/or "shims" (wrong word for me anyway, I like "spacers" better), are probably matched to the set of springs it had installed.
If memory serves, R+D used to offer shorter springs that needed a .100 spring spacer installed under them..

 

Valves don't break because of too much seat pressure, they break because of fatigue and insufficient spring pressure. How much seat pressure do you have with your current setup? how much over the nose? Stiff springs force the bucket/valve to follow the cams profile providing a relatively gentle closing of the valve, soft springs allow the valve to float over the nose and not use the closing ramp of the camshaft resulting in a much more violent closing of the valve and much more stress on the valvetrain. IF THE SPRINGS HAD BEEN SHIMMED TOO TIGHT to the point they were approacing coil bind they would have failed much much sooner. When they failed from coil bind they would have came out in peices(the springs NOT the valves).

You ran it over a year before it failed, how many times did you replace the valve springs? Valves?

Honestly your setting yourself up for failure, those cams are damn sight bigger than the stock cams and require extra maintenance closer service intervals than the stock stuff. They will not work well without high compression to help keep the cylinder pressure up before the torque peak. JMO