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Lap valves on a new engine?


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#1 Trav1s ONLINE  

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Posted July 07, 2015 - 02:17 PM

So I am building a K301 for my '77 JD 312 and I am using a NOS Kohler K301 block and rebuild kit and I am wondering if I need to lap the valves when I reassemble it?

 

 



#2 boyscout862 ONLINE  

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Posted July 07, 2015 - 02:35 PM

I always do. The lapping with the "fine" compound gets a tighter seal. When you check it can indicate if something is wrong. Clean it all real good when you are done. Good Luck, Rick


Edited by boyscout862, July 07, 2015 - 02:36 PM.

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#3 framesteer ONLINE  

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Posted July 07, 2015 - 02:37 PM

Assuming your NOS  block is just that -- the block only, then you should lap the new valves in the rebuild kit to the block.


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#4 Bruce Dorsi OFFLINE  

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Posted July 07, 2015 - 08:41 PM

You don't have to lap the valves, but I would definitely recommend lapping them to verify that all is well.

 

When done, you should see a consistent dull-gray ring around the valve and valve seat. 

 

Don't forget to set valve clearances.


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#5 karl OFFLINE  

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Posted July 07, 2015 - 09:24 PM

It is a custom to lap new valves to new seats with a light grade clover compound.
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#6 classic ONLINE  

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Posted July 07, 2015 - 09:45 PM

Here is a pic of the intake valve and seat from a Briggs ZZ engine. This engine sat for over half a century in an out building. There weren't many hours put on this engine before it was stored in '51 or '52. You can see how narrow the contact surface between the valve and seat is. This is accomplished by grinding the valve at a 45 degree angle and the valve seat at a 46 degree angle. I was pretty impressed when I pulled this crusty engine apart and noticed hardly any wear on anything.

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Edited by classic, July 07, 2015 - 09:48 PM.

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#7 Chopperhed OFFLINE  

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Posted July 07, 2015 - 10:18 PM

Always lap the valves. It makes for max performance and longevity.


Edited by Chopperhed, July 07, 2015 - 10:19 PM.

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#8 Trav1s ONLINE  

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Posted July 08, 2015 - 01:13 PM

Thanks all!  Time to get compound and do a bit more work before further assembly.



#9 Billy M ONLINE  

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Posted July 09, 2015 - 10:19 AM

Good plan.  I always lap new valves.  Like others said, it does make sure everything seats well.  Even when I do just a re-ring job, I remove/inspect and re-lap the valves to make sure the valves and seats are sealing as they should.  It's cheap peace of mind, especially if you are doing it yourself.  Good luck!

 

Billy






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