It’s not the amount of seat run out that there is to some pilot and some gauge. It’s the cumulative package between the valve face and valve seat. Anyone can seal a valve job up with .0015”-.002” stem to guide clearance. Start sealing the valve face to seat with less than .001” clearance and then you will know that the package is concentric and sealed up. Only then should the guides be honed for stem clearance.
In my experiences with valve seat runout tools there was more slack between the pilot being used and the bore within the indicator than the valve stem to guide clearance. I’ve even witnessed one argument over seat runout when the pilot was a tapered pilot and was pivoting in the valve guide. People using expandable pilots to check with, all kinds of numerous ways to introduce errors into the equation. I loathe those tools and doubt the validity in the readings of everyone I see. I know that there are people out there that have nice precise pilots to check with and they’re nice and tight and may very well be showing a true story. It’s just not the whole story. There’s still a valve stem and valve face with concerns for concentricity that has to be accounted for. I’m saying that if a person is going to undertake the task of ensuring concentricity of a valve job then go all the way. People hate lapping valve seats. My guess is that they believe that magic marker ink is thinner than lapping compound and that lapping compound comes in only one grit. I have it from 400 grit all the way up to 1200 grit in 200 grit increments. I can machine a set of heads and show the world a perfect seal with a magic marker on the valve face and on the valve seat at .001” stem to guide clearance. Only problem is that magic marker is not telling the entire story. I can take 400 grit lapping compound and show the world all kinds of sins within the valve seat and valve face when conditions are less than desirable. I.E. valve seats that are too hard or that are too inconsistent in hardness. Valve stems that are not precise. If your chasing precision it’s going to take a harsh look at the entire package. The entire machining process and the limitations that all the equipment combined can work together to create. There’s no shame in a valve job with .002” stem to guide clearance I’ve seen them work for many years. The shame is when it’s not understood that the lack of concentricity contained in the entire package is resulting in a valve stem that is rubbing the interior of one side of the valve guide at .002” clearance causing the guide to seize onto the valve stem. It happens and I could go on and on about it.
@@servediocylinderheadsI really don't see expandable pilots giving good concentricity unless it's on minimum 11/32 valve guides and brand new honed straight guides, valve head size also comes into play on that too, tapered pilots all around are just better, especially when your working with worn guides.
It seems they are always this way. Mass production. Will it run? Yep. Will it last? Will it fatigue the valve and snap the head off? Will it wear the guides? All good questions. Hone guides and recut seats then forget about it.
I know this is old but I’ve run into that before with an AFR head and the conclusion I came to is that because the valve guide was milled by the CNC machine and not square at the end, it was throwing off the pilot. I think that head showed .004” clearance but still vacuum checked really well so I figured it must have been that the checker wasn’t getting accurate readings. I figure that as long as it vacuum checks and seals then it’s all good!
It’s not the amount of seat run out that there is to some pilot and some gauge.
It’s the cumulative package between the valve face and valve seat.
Anyone can seal a valve job up with .0015”-.002” stem to guide clearance.
Start sealing the valve face to seat with less than .001” clearance and then you will know that the package is concentric and sealed up.
Only then should the guides be honed for stem clearance.
So, I am doing it wrong?
In my experiences with valve seat runout tools there was more slack between the pilot being used and the bore within the indicator than the valve stem to guide clearance.
I’ve even witnessed one argument over seat runout when the pilot was a tapered pilot and was pivoting in the valve guide.
People using expandable pilots to check with, all kinds of numerous ways to introduce errors into the equation.
I loathe those tools and doubt the validity in the readings of everyone I see.
I know that there are people out there that have nice precise pilots to check with and they’re nice and tight and may very well be showing a true story.
It’s just not the whole story. There’s still a valve stem and valve face with concerns for concentricity that has to be accounted for.
I’m saying that if a person is going to undertake the task of ensuring concentricity of a valve job then go all the way.
People hate lapping valve seats. My guess is that they believe that magic marker ink is thinner than lapping compound and that lapping compound comes in only one grit.
I have it from 400 grit all the way up to 1200 grit in 200 grit increments.
I can machine a set of heads and show the world a perfect seal with a magic marker on the valve face and on the valve seat at .001” stem to guide clearance.
Only problem is that magic marker is not telling the entire story.
I can take 400 grit lapping compound and show the world all kinds of sins within the valve seat and valve face when conditions are less than desirable. I.E. valve seats that are too hard or that are too inconsistent in hardness. Valve stems that are not precise.
If your chasing precision it’s going to take a harsh look at the entire package. The entire machining process and the limitations that all the equipment combined can work together to create.
There’s no shame in a valve job with .002” stem to guide clearance I’ve seen them work for many years.
The shame is when it’s not understood that the lack of concentricity contained in the entire package is resulting in a valve stem that is rubbing the interior of one side of the valve guide at .002” clearance causing the guide to seize onto the valve stem. It happens and I could go on and on about it.
@@hughobrien4139 Expandable pilots are useless. Watch the "Origins of precision" on youtube. It is right up your alley.
@@servediocylinderheadsI really don't see expandable pilots giving good concentricity unless it's on minimum 11/32 valve guides and brand new honed straight guides, valve head size also comes into play on that too, tapered pilots all around are just better, especially when your working with worn guides.
@dawsonjorgensen3521 I only use solid pilots. Thanks
Crazy ive seen video of brand new AFR cnc heads out of the box 7 to 9 thousands out of round on the seat
It seems they are always this way. Mass production. Will it run? Yep. Will it last? Will it fatigue the valve and snap the head off? Will it wear the guides? All good questions. Hone guides and recut seats then forget about it.
I know this is old but I’ve run into that before with an AFR head and the conclusion I came to is that because the valve guide was milled by the CNC machine and not square at the end, it was throwing off the pilot.
I think that head showed .004” clearance but still vacuum checked really well so I figured it must have been that the checker wasn’t getting accurate readings.
I figure that as long as it vacuum checks and seals then it’s all good!
How much is the maximum runout that you will let go?
.001"
Hi Charles. When you talk about honing the guides, what is the guide to stem clearance you are shooting for? Thanks. Andrew
These are less than .002" with iron guides.
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