Duncans Metal Pages
Seal Major - cylinder block
Last updated: 13 Nov 2018


The block casting is made from light aluminium alloy and cored to produce the water jacket.  Cylinder liners are a light press fit into the casting as are the cast iron valve seats/ports.  The key thing in this section is to get the reference surfaces correct, and ensure all other machining is carried out accurately from these references.

Block1 03-Jul-2005: The 4 jaw chuck has enough capacity to hold the block while the bottom face is machined, providing the first reference face.
Block2 Now the top face can be taken down - it has been left 0.010" higher than it should be to allow a final skim to be made when the cylinder liners and valve ports have been pressed in.
Block3 Machining the face of the valve chest - this provides another plane from which a number of other critical dimensions such as bore and valve positions will be referenced.
Block4 And finally the ends of the block to provide a reference plane in the third axis.
Block5 17-Jul-2005: Boring the hole and relief for the liners is being carried out in the mini-mill; it's easier to line up the bores that way.  The boring operations for the port inserts has already been carried out.
Block6 The top deck is done and some coolant transfer holes have been added.  Holes for the studs have been tapped to 4BA (a guess) as the drawings were not specific on the thread size of the studs.
Block7 Cheap trick - a half inch of packing has been placed under the base of the block casting to get the angle right for the dipstick/filler hole.
Block8 Line boring the recesses for the main bearing retainers.
Block9 Back to the milling machine to drill and tap the holes in the front and rear faces of the block.
Block10 Drilling/reaming the bore for the camshaft bearings.
Block11 That's the block casting done for now.  It will need to have the side drilled for the ports and manifold retaining studs, although that will have to wait until the ports are pressed in.

Next section: Liners and ports


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