Radius job? This too good to be true?

[nitro325is]

I have given up on finding a decent s50 for sale so I'm just gonna throw my m3 cams into an m50 that ive been working on.I took the head to a speed shop to do a 3 angle valve grind but instead they offered a 5 angle and their "ultimate" a raduis job.

To paraphrase what they said

"Technically a radius job offers "infinite" numbers of "angles" since it has more tangential points than can be counted. Picture it this way....imagine alot of water running down a staircase, bounces & splashes all over the place ....now dump that same amount of water down a slide (smooth, curved surface) and the water flows more smoothly. The more angles a valve-job has, the smaller the steps (in the above analogy) become....allowing smoother air-flow into the cylinders."

Are they full of shit? its only an extra $80 for this.

[darien28]

personally, I don't see much of an advantage to this. and having a completely smooth valve/seat won't work well. a somewhat stepped valve surfece (ie machined but not polished) will breate surface turbulence which allows the fuel to be better suspended.

'm not sure if they've done any real flow tests on their radius job, but my bet is that it's not worth it.

[Jon '92 325ic]

Re: Sounds similar to a Metric Mechanics technique....

Sounds similar to Metric Mechanics Surface Turbulence technique. You can read about it here: http://www.metricmechanic.com/pg27.htm. I've never had it done and so can't comment on its effects

[bimmerphile]

I'm going to post this right below since your link didnt work right.

[darien28]

the way I read it, it sounded like the more angles make the surface smoother... which is the opposite of the surface turbulence I was talking about (same as MM's info)