Jump to content

Garden Tractors and Parts on eBay



Photo
- - - - -

Lap valves on a new engine?


  • Please log in to reply
8 replies to this topic

#1 Trav1s ONLINE  

Trav1s

    Got points?

  • Senior Member
  • Member No: 5472
  • 3,072 Thanks
  • 4,220 posts
  • Location: Cedar Rapids, IA

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  

boyscout862
  • Senior Member
  • Contributor
  • Member No: 8923
  • 12,020 Thanks
  • 8,795 posts
  • Location: N.E. Connecticut

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.

  • Chopperhed and propane1 have said thanks

#3 framesteer OFFLINE  

framesteer
  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 11301
  • 403 Thanks
  • 192 posts
  • Location: East Moline, IL

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.


  • Chopperhed said thank you

#4 Bruce Dorsi OFFLINE  

Bruce Dorsi

    Old, but not dead -- yet!

  • Senior Member
  • -GTt Supporter-
  • Contributor
  • Member No: 1525
  • 3,899 Thanks
  • 2,445 posts
  • Location: New Jersey

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.


  • Bolens 1000 and Chopperhed have said thanks

#5 karel OFFLINE  

karel
  • Senior Member
  • Member No: 38218
  • 1,897 Thanks
  • 1,279 posts

Posted July 07, 2015 - 09:24 PM

It is a custom to lap new valves to new seats with a light grade clover compound.
  • Chopperhed said thank you

#6 classic ONLINE  

classic
  • Senior Member
  • Member No: 52970
  • 4,878 Thanks
  • 2,150 posts
  • Location: New York

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.

Attached Thumbnails

  • 20141103_212257-1-2.jpg

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

  • olcowhand and Chopperhed have said thanks

#7 Chopperhed OFFLINE  

Chopperhed
  • Senior Member
  • Member No: 20120
  • 1,852 Thanks
  • 1,071 posts
  • Location: Edmonton, Ab, Canada

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.

  • classic said thank you

#8 Trav1s ONLINE  

Trav1s

    Got points?

  • Senior Member
  • Member No: 5472
  • 3,072 Thanks
  • 4,220 posts
  • Location: Cedar Rapids, IA

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 OFFLINE  

Billy M
  • Senior Member
  • Contributor
  • Member No: 15999
  • 611 Thanks
  • 526 posts
  • Location: Carlisle, OH

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






Top