Here you can see the tops...
Here you can see the tops of the valve guides. Each valve is mated to the guide to ensure smooth operation at high rpm.
Once the head was finished being reworked by Portflow, Tom hand-lapped each valve per NPD's request. A gray ring should form 360 degrees around the valve and valve seat. Although head specialists like Portflow perform vacuum testing, not all do. Vacuum testing on its own is great, but hand-lapping promotes a sense of break in between the valve and the seat, in conjunction to creating a contact patch that's visible to the builder. NPD's belief is that the responsibility of final assembly falls on the shoulders of the engine builder and not the machine shop. These details should be examined by the builder prior to assembly. Each valvespring is then checked to ensure that they're equal and up to manufacturer specifications. In this case, we're using Supertech dual valvesprings with a seat pressure of 225 pounds and an 11.8 lift.
The factory surfaces the head...
The factory surfaces the head to a coarser finish than what we have. This is, in part, because the stock gasket material is softer, but much less durable than our metal gasket.
Final assembly was performed using Supertech titanium retainers, buckets, and shims. Instead of the factory-style outer shim, Supertech switches to an inner shim-type bucket. This frees up about 32 percent in weight from the bucket assembly and helps in reliability during high rpm operation. Although there's a port on the front water neck, which can be connected to an air separator tank, we opted to incorporate Auto Staff's water bypass block. This provides an additional source to remove any trapped cavitations in the cooling system.
While this much work may seem a bit excessive, this is the standard amount of effort and consideration that should be taken into building a motor of this caliber. These techniques can be applied to any high-performance motor build. Stay tuned for the next installment as we take a visit to the machine shop to have our KA24DE block bored and honed.
Each spring is individually...
Each spring is individually tested on a valvespring tester to ensure that all the seat pressures match to the manufacturer's specifications. Here we are testing the outer spring.
On the left is the stock bucket...
On the left is the stock bucket and shim and on the right is Supertech's inner shim-type bucket. The Supertech bucket drops the overall weight from 50.3 to 34.2 grams.
An Auto Staff coolant adapter...
An Auto Staff coolant adapter is installed on the back of the head to remove the factory freeze plug and relieve any cavitations trapped in the head.