Salvage an Engine Block

J

John Price

New member
Help! I need the experience of some Barners who might have experienced this! I have invested a significant amount in what looked like a very good A block; it was magnafluxed, got valve seats, fitted pistons, good babbit. As a last detail, I chased the head stud holes with a tap. When I got to the threaded hole between cyls. 3 and 4 (on the valve side) the tap popped off the "casting dome" at the bottom of the hole. I now have a hole into the water passage below! I retrieved the broken piece of casting; it was very thin and porous at the point of fracture.
I am thinking of a threaded plug that would be only 3 or 4 threads thick, screwed down to the bottom of the stud hole and locked in place with epoxy or some form of Loktite? There will still be enough full threads in the block to fully engage the head stud. Anybody ever heard of this approach, or a better one? I don't think it could be heated enough for solder or braze? I'm confident it would last for a while, but how about a lifetime? All thoughts greatly appreciated!!
 
i dont see why a shallow set screw wouldnt work...just make sure you can get far enough down with it to not interfere with the head stud. use whatever magic lock goo you want to hold it in place. (green loctite will have it in there forever - takes a cuttign torch to break that bond)
 
rule of thumb with studs is the stud needs to bury in the stud hole equal to the studs thickness for maximum torque. Ford left more than enough room for a locktited plug,make sure and clean the hell out of it with acetone or brake clean before setting the plug with red locktite..test fit the plug first...let it cure 24 hours before assembly.
 
Coat the threads with permatex old time gasket sealer to stop water seepage and don't worry, the stud won't pull out if you have good threads.
 
Be careful about using a modern tap to chase threads in an old block. You will more than likely remove some metal along with the grunge, resulting in a loose, sloppy fit for the stud. Just use a thread chaser tap.
 
Last few modern engines I rebuilt didn't have blind holes. Had to get a tube of combination thread lube and sealer. Believe it was Permetex brand. 220,000 miles so far and at least the headbolts are not leaking.
 
Hardware taps are not the right class for the studs in your engine. The factory used a tighter class for studs. Also against popular belief studs should not be screwed in tight. back them out a 1/2 turn. If you do it that way you can get the head on and off easier. when you screw them in tight they tend to lean a little, especially when the wrong tap was used.

It will be ok but it does weaken the studs threads in the block. Easier to strip the threads.
 
I have rebuilt many engines with a head stud open to the water jacket. I seal the threads with Permatex Right Stuff. I have never had a leaker.
Don't do the plug under the stud. It is best to keep all the threads available securing the stud.
Good Day!
 
Gents! Many thanks for all the insights! I have some options to consider, but most importantly I am convinced that the problem is not a show stopper! Just need to decide which way to skin this cat! John
 
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