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I'll be attempting my first head gasket job on my 1996 Discovery 1 in several weeks and I'm trying to get all the pieces together now. I've read plenty of write-ups and other documentation but I cannot find a consistent answer on head bolt prep prior to reinstalling the heads. Those of you who have done this job how did you prep the block/bolts? I will have all new hardware, but I've read some guys use motor oil on the threads and grease under the bolt head. Is this necessary? I imagine the grease under the bolt head would affect torque values. Furthermore, I'll be cleaning the block side holes with brake clean and compressed air, so is it necessary to chase the thread on the block?
Last edited by _ExpeditionMan; Jan 27, 2019 at 03:54 PM.
I chased the threads in the block with an old head bolt with 2 slots cut in it aka a tap. Prior to the new bolts being installed I also dipped them in motor oil per ABs HG video for the D2.
Its not a hard job, take yer time and lots of pics. Also ziploc bags and a sharpie are your friend!
Use oil on threads per the manual and anti seize under bolt heads (normal machine prep), prevents galling. Chase threads with a blind tap (I grind the first 1/4" off to bottom thread cutting), dresses them again to prevent galling. What head gaskets did you get? Also if you don't have one I'd suggest buying a 1/2" degree wrench for the two 90* turns, just removes the guess work, makes the turns more precise. If you can't get to the back set of bolts unbolt the motor mounts and lower the motor enough to get to them squarely, that is critical as they clamp the head to the block coolant passage and the gasket and port is very thin walled.
Use oil on threads per the manual and anti seize under bolt heads (normal machine prep), prevents galling. Chase threads with a blind tap (I grind the first 1/4" off to bottom thread cutting), dresses them again to prevent galling. What head gaskets did you get? Also if you don't have one I'd suggest buying a 1/2" degree wrench for the two 90* turns, just removes the guess work, makes the turns more precise. If you can't get to the back set of bolts unbolt the motor mounts and lower the motor enough to get to them squarely, that is critical as they clamp the head to the block coolant passage and the gasket and port is very thin walled.
Thanks for the response. What size of blind tap do you use to chase the threads? Definitely want to make sure I get this correct.
Another excellent tool to have on hand is a Mayhew Stud Extractor for if/when one of the head bolts breaks.
When you need on of these it's worth every penny.
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I was about to say, DON'T YOU PUT THAT EVIL ON ME! Appreciate the input guys, took down both of these as notes. Better to be prepared than stranded halfway through a job.
I did my first head gasket and cylinder head replacement several months ago. Reading from this forum combined with watching this video several times helped.
Land Rover - Range Rover - Head Gasket Replacement
Prepping for first head gasket job - D1
