IgorT.455/406

really, how many ppl. have opti bearing fail? I know some, but what's the most common problem? Moisture invasion and cap/rotor age?

Mine was cap/rotor worn.

Steve0

That depends on the applied load and the velocity of the rotation. A bearing is not better than a bushing just because its a bearing.

Kevin Blown 95 TA

Then ask yourself why GM changed it.

Steve0

What was GM's deisgn history? It could have been something as simple as GM was able to source a bearing from a supplier for cheaper than a comprable bushing.

From looking at it, it's not like an opti spark distributor faces much in the way either thrust or axial loading. It is also not a notable source of drag on the motor. I really don't see there being much advantage to either design in this particular application as long as its properly lubricated and sealed. All I'm saying is you cant make blanket statements like "a bearing is better than a bushing" without some reasoning behind it.

Perhaps someone with more experience on machine design would be able to give some insight.

Blue96z28

I agree with the bushing theory, it should not be ruled out as an upgrade just because it uses a bushing instead of a bearing. It would seem that a bushing would allow for closer tolerances than a ball bearing, I would think anyway, by tolerances I mean the concentricity of it while rotating, would seem a bushing would allow for less movement(wobble of axis) therfore maybe more accuate for the optics? This is of course given it doesn't wear. Dunno.

Either way, I want to hear more people chime in on the accel, the good and the bad, lets hear it.

Kevin Blown 95 TA

I do happen to have a lot of experience in machine design, and also in cost reduction. And when you do cost reductions, you go might go from bearing to bushing, not the other way around unless you got a China made bearing and a US made bushing . The bearing was put in there to make it last longer and get rid of the problems caused by wear at a cost penalty.

I'm not implying that bushings don't have their place, because they definitely do, and a lot of it depends on space, speed, load like was mentioned, friction, etc. I've had salesmen show me the latest permanently lubed sintered bushings with all kinds of high-tech dry & wet lubes impregnated into them, but when you really want something to last, you try to find a way to get a sealed precision ball or roller bearing into it. In the days when all cars ran with conventional points style distributors, one of the real problems was dwell variation which was caused by worn distributer shaft bushings. So that is still in the back of my mind. When I bought a nice dual point aftermarket distributor to replace it, guess what? It featured sealed bearings.