intake cam/exhaust cam redux...

[tomacGTi]

After replacing the stem seals one last time, the intake/exhaust cam came is out and the stock exhaust cam is back in.

After visually checking the clearances on my bad head and also the evidence that the lift is a bit much on the exhaust side, I switched back. When static, the bottom of the retainer has about 1mm or so of clearance from the top of the valve stem seal. Obviously when turning near 14k and several times a second, that value goes down and eventually the bottom of the retainer smacks the top of the stem seal.

The one month old APE seals had some very obvious witness marks to what did them in. I thought it was heat at first but it's pretty obvious that it's impact.

Besides that, this swap isn't really as straightforward as the swaps the guys on the SV boards do. If you've ever held a B4 or GSXR cam in your hands, you realize the lobes are very particularily shaped as far as opening and closing before the tdc/btdc. On an SV, it looks like a normal cam lobe, very asymmetrical so the cam doesn't mind spinning the other direction. With the B4 cam, it puts these opening and closings at different points thus changing the cam's profile entirely. To visually line up the lobes as best as possible, it's also necessary to advance the cam about 8* and even then the opening and closing is a best case scenario. The TDC points hit much earlier than the factory exhaust and affect the power delivery.

So there you have it. It would work if the valve guide were modified by shortening and even then it still isn't perfect. I have to admit though, when I was running it the power was great.

-Randy

[Red01]

On an SV, it looks like a normal cam lobe, very asymmetrical so the cam doesn't mind spinning the other direction.

I think the right word here is "symmetrical" 

As you're decribing it, the B4 cam is asymmetrical and the SV650 cam is (more) symmetrical.

From Hot Rod's tech articles on cams:

Definition: A symmetrical camshaft makes use of the same profile on the opening and closing side of a specific lobe. In other words, the opening side of an intake lobe features a shape that is exactly the same on the closing side of the lobe. This term should not be confused with single-pattern or dual-pattern camshafts (see below).

Definition: An asymmetrical camshaft features a lobe shape or profile that is different on the opening side than the closing side of the same lobe. For example, a camshaft could feature a very rapid valve opening profile, but when the valve is closing on the same lobe, the shape could be extremely smooth and gentle.

...just keepin' ya honest. 

[tomacGTi]

Ya got me Paul.

After working on the thing again for upteen hours yesterday, semantics were not a strong point. Lots of four letter words though!

[Red01]

Been there, done that, wore out the T-shirt.

Kind of like the problem with my pickup that's been kicking my ass. 

[gsxr400 racer]

My appologies then on saying it works maybe i did not have it in long enough to notice that problem or maybe i didnt have the problem due to i added some valve spring washers to mine.

[tomacGTi]

Bah, don't apologize Jay. Not your fault at all. It doesn't work and that's all there is to it. If anything, I figured out how to do stem seals without separating the head from the motor.

I thought about extra washers and the like but all that would have done is increased spring pressure and perhaps introduced coil bind (worse situation). The retainers would have still smacked the tops of the stem seals and it would be another mess. The exhaust valves are .5mm taller than the intake hence the shim under the lower retainer. That combined with the additional lift just spelled disaster for the seals.

The other downside with additional shims would have been the possibility of tuliping the valves and smashing the seats with the increased pressure. You could also introduce premature wear to the lobes of the cam and the wiping surface of the rocker.

Really, the only cam swap I can see that's viable would be one purpose made. Seeing that there were never many options and that the info from folks that have done them in the past no longer exist, it's hard to say what's to gain. Looking at the profiles next to one another, it's apparant that Suzuki did alot of work to optimize what they had. Degreeing the cams would have benefit as well.