Pulley run out?

[cjperformance]

Got to say I would use and have used water pump , alternator, aircon, power steer pulleys with that runout and more. These go on to do many miles without problem.
One of my own 4.0L 6cyl hacks , purchased at 279000km had a visible large wobble in the balancer pulley which is part of the outter balancer ring, aprox 2mm/.080" at a look by eye. That same engine and balancer are still sitting here, the car retired at 498000km, the engine, and all pulleys intact.

[justahoby]

Exactly. I never knew they would even worry long before .0025 off on a pully. I see a lot of new cars where there is a few thousands of pully off center vibrating the belt without being obvious even revving it. I say that perfect .. send it!

[midnightbluS10]

There is the time I put the power steering pump pulley on backwards on a GM pump while working at my first Chevy dealership as a technician lmao. Since it was backwards, I had no lip to use the tool on to get it back off so I had to use a 3 jaw puller around the edge. It obviously bent the pulley out of spec and you couldn't just buy a new one at the time. So instead of making a warranty claim or something else, the tech in the stall next to me brought over a BFH and we knocked it into submission. It still had runout but I'm not sure how much. It was barely enough to see with the naked eye at idle, IIRC.

Don't know if there were ever any issues, either. It never came back while I was there, so I assume it was OK.

[Ericnova]

With the flex and stretch of a vee belt (or cog) drive I don't see any way 0.0025" TIR could have any effect.

The stock OEM pulley has the shaft hole accurately punched and the pulley will have very little, if any, runout. Several years ago I was a product manager at one of the large US engine parts manufacturers and one of my product responsibilities was water pumps. All of a sudden we began having warranty issues for particular water pump on Medium Duty Chevrolet and GMC trucks with 366 and 427 engines. These are not high RPM engines by any means, but we were paying out huge labor claims because the shaft/seal assembly was breaking and sending the fans through radiators and even the hood in a couple of cases. We tracked the problem down to the manufacturer who was supplying the shaft/seal assembly to us for these pumps. Metallurgy tests showed that the quality of the steel was good and it took awhile for us to find the real problem. The pump shaft used a couple of rows of ball bearings and the manufacturer had begun using a new supplier for ball bearings without notifying us. The print specs called out that the ball bearing diameter tolerance was something like +/- .00003" and these ball bearings did not always fall within that tolerance range. The difference in ball bearing diameters resulted in harmonic vibrations which would break the pump shaft, causing all kinds of mayhem. THIS is the reason why I would not use the pulley that shows "only" .0025" run-out . . . . . . . .

As a machinist, you should know that ball bearings out of tolerance in a bearing assembly and the belt groove on a pulley are two completely different things. Not even remotely comparable.

I dare you to show me an actual production GM pulley with less than .003" runout.
You're gonna search for a looooong time....

[engineguyBill]

If the shaft pilot hole has been redrilled, thus putting the pulley into a non-concentric situation, then it is very possible that undesirable harmonics are introduced into the pump shaft/bearing/seal assembly. Bottom line, use a pulley that is designed for the pump being used . . . . .

[modok]

it is designed for the app, He designed it himself, hopefully with a uni-bit and not a twist drill.