Once the block is properly prepped, Engine Supply straps the block to the bore/hone machine. We made sure to supply them with a torque plate to use when honing the block. This keeps the amount of distortion down during machining. NPD explains that with the head torqued down, depending on what type of deck-open (i.e. Honda) or closed (i.e. Nissan)-it is, how deep the head bolt threads sit in the block, and the overall length of the cylinder, the block experiences distortion. Some may argue that under operating temperature, the block may distort differently. But machining with a torque plate reduces the amount of distortion created by the head studs pulling against the block. To truly simulate head torque distortion, we use the same type of head gasket that we'll be running during machining.
Engine Supply makes a couple passes with the bore machine to determine how much material is taken out. Remember it is easy to enlarge the bore; it's impossible to make it smaller. We're going from the stock 89mm bore to a 90mm bore. Having a general reference of how much material each pass takes off gives them a general idea of how long they need to bore the block to get to the general area they need to be in. Once the machining is done, we measure the block again. We're within our 0.01mm out of round tolerance and the final hone is within our piston-to-wall clearance. Our block is now ready to be taken back to the shop to be assembled.
Having an engine machined sounds complicated but it's really cut-and-dry. Basically, you have target numbers that you want to hit and a small window of tolerance. If your block measurements are somewhere outside of this range, then it's time to send it back to the machine shop or consider another alternative. Remember this can be applied to any engine build. Measuring in the build process lowers the risk of problems on the street or track. Check out our next installment as we start the assembly process of our KA24DE(T).
Ultra Performance Machining
NPD (Distributed by AP Boss USA)
Lubrication oil is fed as...
Lubrication oil is fed as the boring/honing operation is being performed. The oil keeps the boring/honing bit and cylinder surface cool, preventing distortion of the cutting surface and prolonging the bit life.
Ultra Performance Machining...
Ultra Performance Machining periodically measures the cylinder during boring and honing to check cylinder taper and out of round.
Ultra Performance Machining...
Ultra Performance Machining adds a chamber to the top of the cylinders. This drastically reduces the risk of piston ring damage during the final assembly of the engine.
The oil pump is mounted to...
The oil pump is mounted to Ultra Performance Machining's custom fixture then resurfaced the proper amount to match the height of the block's deck surface.
When resurfacing the block...
When resurfacing the block a common mistake among many KA24 owners is also resurfacing the oil pump. Failing to do so effects the final deck height and proper head gasket seal.