Seat run-out gage

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cgarb
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Seat run-out gage

Post by cgarb » Mon Apr 16, 2018 8:55 pm

I bought a valve seat run-out gage that had just showed up today. Checking it out and testing it on a few seats. It is a Fowler brand gage that you set a ball tipped pointer on the 45deg and the indicator rides on the end of the pilot in a ground sleeve. Radial run-out shows up by moving the sleeve up and down on the pilot and moving the indicator plunger. Is the actual reading on the needle true seat run-out or is it half of the actual run-out with that style gage?

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Re: Seat run-out gage

Post by modok » Mon Apr 16, 2018 9:02 pm

That is the most common type of gauge that is used to check seat runout.

I think it is safe to assume if you read or hear a certain specification of seat runout, it is the same as what that reads.

Is that a "true" measurement or not....maybe it isn't, but it's a standard. I mean, in the manuals, if they have a picture of it they have a picture of THAT type. I was just reading a 1964 motor manual today looking up specs, and it's in there.
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Re: Seat run-out gage

Post by ProPower engines » Mon Apr 16, 2018 9:29 pm

I had just got that same gauge brand new about 2 months back for my apprentice to use when checking seats.
Yes the reading on the dial will give you an accurate run out reading but as a caution that little ball end has to be dead nuts on the seat center to get an accurate reading of how much run out is present on the seat.

It took a couple days for my guy to come and ask if he was doing something wrong on the practice heads he was doing and after looking at it I figured out the ball needs to be centered but there is also a way to influence the gauge to give a higher reading then what you actually have for run out.
By just lowering the gauge to the seat and giving it a spin will induce more run out then you have. You must be very gentle when rotating the gauge to get an accurate reading.
the other deal is quality straight pilots are an absolute must which I am sure you have but I did find a bad pilot when using that gauge so it is a good idea to check any long time in service pilots for tweaks in the end of the pilot.
Also any wiggle when using a tapered pilot will piss it off a ton as well since we are shooting for .0005" or less runout.

I am sure you will be able to get it right after a few tries with it it took me about an hour to get the whole thing dialed in :D
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Re: Seat run-out gage

Post by cpmotors » Mon Apr 16, 2018 10:13 pm

I think of it more as a perpendicularity gauge.
Meaning high side vs low side.
High side being the low reading.
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Re: Seat run-out gage

Post by modok » Mon Apr 16, 2018 10:37 pm

Sensitive to wiggling?? It's probably just not made well.
The sioux X825a was a good fit on their pilots and had a starrett 196 back plunger indicator.
Just that indicator is 150$, in five years ago dollars. When I break one It HURTS :x
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Re: Seat run-out gage

Post by ProPower engines » Tue Apr 17, 2018 1:26 am

modok wrote:
Mon Apr 16, 2018 10:37 pm
Sensitive to wiggling?? It's probably just not made well.
The sioux X825a was a good fit on their pilots and had a starrett 196 back plunger indicator.
Just that indicator is 150$, in five years ago dollars. When I break one It HURTS :x
The gauge is well made I was referring to a tapered pilot in the guide wiggle. also depending on how much time pilots have seen driving stones also would be an issue if wear was any more then a couple 10th's on the top side.

I was just trying to point out it was a sensitive gauge and like any sensitive measuring devise it will deviate from true when extra force is incorrectly applied,
Having used the same gauge for over 20 years I was just comparing a new one I just got to a rookie using it to a more experienced operator. They both need to learn the sensitive feel of the device for accurate measuring.
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Re: Seat run-out gage

Post by cgarb » Tue Apr 17, 2018 1:44 am

I was asking because I bought a set of eBay special SBC aluminum heads and was checking out of the box seat run-out. I was surprised how good they checked. Most within .002" only found one that was out .004. That's what got me thinking, is this gage giving me full run-out or only half the actual run out.

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