Joined: Jan 2022 Posts: 75 Threads: 18
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Location: cambridge
Car type: A7 special 34
I have just bored, ported and tinkered a rebuilt block fo replace the one we found pourous. Its ready to go back in but in my quest to make a good one I have come across a few blocks at the back of the shed from various places and note that they all have the same failure mode with a crack from the centre stud through to the water way. I was wondering as I always like to have a go, what are the oprtions people have tried and how succsessful have the repairs been. So far my ideas have been.....
-Pay and have the crack laser welded
-Grind out the crack, preheat and have a go with the TIG welder using Sifbronze No8 rods. This has woked in a few other spots we were in but mostly with the steamer.
-CNC a dogbone section out between the holes and make a similar shaped stitch a little undersize. Warm the block up and tap the stitch in.
-Fit a commercially available stitch.
Joined: Feb 2024 Posts: 8 Threads: 1
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Location: bellingham wa. usa
Car type: austin nippy 1937
I have stitched up freeze damage in a couple cast iron blocks and was astonished at how well it worked. it was the simple overlapping plug system. I would do that over welding any day, lots to go wrong with welding iron.
Good luck
Randy
Joined: Aug 2017 Posts: 1,338 Threads: 34
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30
Location: Cheshire
Car type: Race Ulster, 1926 Special, 1927 Chummy, 1930 Box
You could have it stitched, but really, as long as the crack is running between the stud and the water jacket and not into the nearest cylinder, it’s not something I’d worry about too much.
Alan Fairless
Joined: Aug 2017 Posts: 921 Threads: 18
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Location: North Yorkshire
Cracking around the centre stud is very common. Unless it is affecting one of the cylinders I wouldn't worry about it. If you use some copper based silicone sealant on your head gasket it should take care of it.
Joined: May 2018 Posts: 2,118 Threads: 111
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Location: Llandrindod Wells
Car type: 29 Special, 30 RK, 28 C Cab
Hi
If you leave as is make sure to seal in the centre stud with some sealant. There is a water path across the crack and up the threads ending up spurting out of the centre head stud!. Also make sure the centre stud is set well down in the block as the crack might weaken the thread near the top of the block.
Cheers
Howard
Joined: Aug 2017 Posts: 104 Threads: 3
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It may also help to tap out the stud hole to 3/8 BSF and use a stepped stud, coated in sealant.
Joined: Jan 2022 Posts: 75 Threads: 18
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Location: cambridge
Car type: A7 special 34
Thanks for the answers I may see about getting a couple of the bridging stiches from metalok at some point but concentrate on getting the new engine ready so it can be fitted after the Cobham trial. We really have enjoyed the event the last couple of years, very friendly and laid back, just the competion in the car I have to watch out for as a husband and wife team things get very competative when we double drive an event.
Joined: Jan 2019 Posts: 48 Threads: 9
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I've had several blocks with this problem and talked to other owners with the same problem. For standard spec road engine you can just avoid tightening that stud as tight as the rest and add some sealant around it when you refit the head. If you aren't getting coolant in the cylinders themselves (look for combustion chambers that appear 'steam-cleaned') then i wouldn't worry too much.
On blocks i have raced with the same crack, i've drilled down into the base casting of the water jacket, drilled a slightly oversize matching hole up from the underside of the block, then tapped a 5/16 thread in the base of the water jacket to take a much longer stud. I can draw a diagram of this modification if that is helpful.
