Lock & Stitch Part 1

Here’s an example of the force that frozen water can have on an otherwise robust cast-iron block. The pictures show a Jaguar 4.2-liter block from an E-Type that has been recently magnafluxed. According to Wikipedia, this process creates a magnetic field around the block which “will cause a high concentration of magnetic flux at surface cracks, which can be made visible by dusting iron powder”. In this case the problem area was painted blue and dusted with yellow iron oxide particles that easily show cracks at the surface.

The results show the weakest point of the water jacket around the block deck. The cracks are the direct result of water expanding during freezing. As this engine belongs to a matching-numbers car, the block will need to be repaired vs replaced. This will require a metal stitching process since a straight-forward weld can further crack the block as the weld cools. To successfully make an electric weld, the entire block would need to be preheated somewhere from 900º to 1500° which isn’t feasible.

The following pictures show definite cracks along the top of the water jacket. The first image shows signs of a previous metal stitching process and the circular pins that replaced the crack are only visible from the Magnaflux process. Either this fix caused crack to extend or the previous repair didn’t cover the entire crack; there is a noticeable seam beyond the pins which extends to the yellow arrows.  Some versions of the lock & stitch fix include expanded bolts which can further stress the area. To prevent this we will use the Lock-N-Stitch Inc’s C1 pins that do not expand. The opposite side of the block also has crack which is unrepaired and will require the same process. The last picture shows one of the C-Series pins next to the crack it will eventually replace.

Further posts will show the compete build of the Jaguar 4.2 including a detailed look at the Lock & Stitch process.

1 Comment to Lock & Stitch Part 1

  1. Patrick Forestell says:


    Did you notice that the block and head gasket both have small water jacket holes between the inner two bores (3 and 4) ? Yet the head lacks these two small water jacket holes ! Presently, I am having my 4.2 E head modified to include the two small water jacket holes as without them, the area blows coolant out past the gasket and overheats (of course).

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