[Dave in MN]

REPOST from 2014:

The repair shown below solves the problem with coolant leaking around a head stud and nut from a cracked head. Repaired...they don't leak!

The repair involves installing a cast iron sleeve in the stud hole that has a crack that runs into the water jacket. The sleeve is made from a cast iron valve guide.

Here is the cast iron guide and tooling info to complete the cracked head repair.....

The cast iron guide I use is available from Engine Parts Warehouse and possibly other sources.
The guide is: SBI #1408591
Outside diameter: .5635"
Length: 4" (I would have chosen a shorter guide...but couldn't find one...)

The ream is sized to be .001" smaller than the outside diameter of the guide. I use one from Rock River Tool #246518
Size is 9/16" or .5625"

The drill bit used to prep the hole for the reamer is a 9/16" undersize that mic's at .560".

You can use any cast iron guide that has an outside diameter close to the size above. I chose this particular guide because it left a reasonable amount of the original cast iron in the head available to surround the guide and the required .5625 (9/16") reamer is readily available. Don't go to much larger or you may machine or break into the water jacket area. When choosing the components you will use, the important thing to keep in mind is that you should have about .001" interference fit. Note that the ream referenced above is .001" smaller than the guide. The guide I chose has a chamfered end to make it easier to install and to allow the Loctite to build between the guide and the head as it is pressed in place...a sharp edge would just wipe the Loctite from the surfaces. I use a Bridgeport but you could use a good drill press...clamp the head on parallel bars top side up, locate the center of the hole being repaired, drill the hole and then ream the hole from the same "set-up". Remove the head to prepare for pressing the guide in place. I lightly but completely coat the surface of the drilled hole and the guide with Blue Loctite Gel and press it in place leaving a bit of the guide protruding from each side of the head. After installing the guide, rough cut the excess on both sides with a cut off blade installed in an angle grinder. Carefully grind the gasket side flush knowing that the final surface will be cleaned up when the head is surfaced. (I always lightly surface the head after making these repairs but it would not be necessary if the head was straight and you don't mess it up when flushing the guide.) The top side is then milled flush with the original surface. At this point the installed guide is drilled the same size as the original stud holes. The size of drill escapes me at the moment... just match the size to the original holes. I have included a photo of the items needed for the repair, two photos of the installed guide and a micrometer showing the size of the undersize drill bit.
I often repair two locations in a head as the adjoining hole to the distributor often has a similar crack. The installed guide photos below show the repair prior to the head being surfaced.

Let me know if you have any questions.
Good Day!
www.durableperformance.net
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