Pulley run out?

[88bluestar]

Got a 3/4 shaft water pump and had to drill out the 5/8” pulley hole to 3/4”. Did not get it dead on and has run out, just curious if you all think it’ll work. It’s about.0025 run out. Very minute wobble but just want everyone’s thoughts.

[Alaskaracer]

If it were mine I'd get the right pulley. Some on here will tell you it's ok, but not on my stuff........

[SupStk]

If it's only 2-1/2 thousandths i wouldn't worry about it, but if you meant twenty-five thousandths it's time for a different pulley.

[BigBlocksOnTop2]

You are real good with a drill bit and .0025'' run out! Run It!

[midnightbluS10]

Got a 3/4 shaft water pump and had to drill out the 5/8” pulley hole to 3/4”. Did not get it dead on and has run out, just curious if you all think it’ll work. It’s about.0025 run out. Very minute wobble but just want everyone’s thoughts.

Why cheap out on a pulley? It can't be more than $20 or $30. IMO, that's worse than cheaping out on headgaskets and reusing them on a $15k dollar engine because you don't want to spend another $125

[engineguyBill]

I would replace the pulley. .0025" is not much runout, but it can be disasterous at high RPM. This much runout can wipe out water pump seal and bearings in very short time.

[BOOT]

What is the pulley drive ratio, over or under? I've never checked any of my pulleys for run-out nor the water pump hub. Now I've used a cheap china water pump and it bent the pump shaft. It wobbled a bit n I ran it that way for awhile, never threw a belt but highest rpm the pulley saw was 4200.

[Dutchman]

If it's a hard to find or unobtainable I would chuck it up in a lathe,indicate the outside then bore the center to a nominal size and make a steeped bushing bringing it back to 5/8. A pretty easy fix.

[MadBill]

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. Per Boot, how many guys religiously check the radial and axial runout and vee width variability of all their pulleys and for anyone that does, what tolerances do you accept ?

[77cruiser]

Factory stamped pulleys aren't exactly true.

[88bluestar]

6800 rpm. oval track engine. Probably going to side with getting a new pulley. Water pump is new and has a 3/4" shaft.

[jake197000]

.0025 ?I ve never checked but id bet most new cars have that much or more I t woulnt bother me .

[Ericnova]

6800 rpm. oval track engine. Probably going to side with getting a new pulley. Water pump is new and has a 3/4" shaft.

If that was .0025"(two and one half thousandths!) then you are wasting your money. That's less than the thickness of a human hair!!!
Hell, crank at .0015" snout runout and .002" bearing clearance has that much runout.....and that'll be every other engine you are racing against and including yours....are they all going to fly apart or eat bearings because of it?? NO.

Ever seen how bad a factory water pump pulley runs out, and pumps last 100,000 miles??

If it was .025(twenty five thousandths0, now you've got reason to maybe get another..

I built circle track and Sprint car wheels, both aluminum and steel 2-piece.....and the company run-out limit was .050". Never had a comeback or complaint for run-out causing a problem.

[engineguyBill]

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 . . . . . . . .

[modok]

So....What's the runout on the the crank pulley?
How you even check that......big ball bearing on the end of the indicator?