This article will likely be one of the most controversial I've ever written. Before anyone objects to what I have to say, read this disclaimer. All of the recommendations in this article are the result of what Buschur Racing has found to work as both a race team and parts manufacturer. As a company, Buschur Racing stands behind its products and technology. We truly believe that if you take this information to heart and then to the track, you won't be disappointed.

Now, there is no way that one could cover every single aspect of the cylinder head sealing, cylinder head modification and camshaft selection in one article. However, we hope to give a very general idea of what we have tried ourselves.

The 4G63 Foundation
Mitsubishi must be full of some very hard core engineers as the early 1990-1992 4G63 is quite possibly the best four-cylinder engine ever built. There is no need for sleeves, aftermarket cranks or much of the other high-dollar parts required for competition with many of the other four cylinders being used in import racing today. On the top end, the cylinder head is also a work of art as little work done to the right places can make tremendous gains. Keeping the seal between the block and head may be one of the easiest tasks of all.

The Golden Seal
In high-performance engines, the head gasket is one of the most critical components. A failure of the gasket and the crucial seal between the cylinder block and cylinder head can result in a loss of performance and extensive parts damage.

The Mitsubishi 4G63 engine uses a high-strength cast-iron block mated to an aluminum cylinder head. The head and block are fastened by 10 head bolts from the factory. The factory uses a composite gasket fitted with a stainless-steel combustion ring.

There are a number of multi-layer steel and copper head gaskets available for the 4G63. There are also countless numbers of techniques that can be used in an attempt to achieve this critical seal. Buschur Racing has tried o-ringing the block, using aftermarket steel gaskets, using copper gaskets, using receiver grooves in the block and putting the o-ring in the block and a receiver groove in the head.

In our experience, nothing has worked as well as a simple set of ARP studs, a stock Mitsubishi head gasket and a stainless-steel o-ringed head. We simply place an o-ring in the cylinder head and use a factory Mitsubishi head gasket. This setup has proven to seal so well that we have destroyed other parts when we should have just blown a head gasket.

In addition to the 4G63 powerplant, this technique has worked well on other cast-iron block/aluminum-head combinations. Give it a try. This goes to prove that sometimes the simplest solutions are also the best.

Getting the Shaft
It seems as though everyone and their brother has released a camshaft for the 4G63. HKS was the first company that offered cams to the U.S. market, as far back as 14 years ago. We have tried or tested against quite a few other brands. We have even had our own custom grinds done. Bottom line is short and to the point. Going too big just doesn't seem necessary. A properly setup 4G63 will make power on a continuous uphill climb to over 10,000 rpm. The engine can also make power low enough that at a 3,000 rpm roll you can rip the tires off of a street car. Since there are quite a few brands that work, our final recommendation is to not go too big and the latest greatest thing may really not be as good as the tried and true.

Spring Forward
The valve spring is another area that needs to be considered on a high-output application. Fortunately, the factory valve spring works extremely well. Remember that too much extra spring rate will only increase wear and potentially rob horsepower. Many companies currently manufacture aftermarket springs. In our experience, many of these springs test no better than the stock and some are even at a lower rate than stock. The stock spring can be successfully used on all but the most aggressive combinations. Always check with the camshaft manufacturer for their recommendations and then have the machine shop check the spring rate of the springs.

For the majority of our applications, we use the stock spring fitted with a shim under them to increase their seat pressure. Be sure to check for coil bind when attempting this as too thick of a shim will cause the springs to coil bind with some camshafts.

Removing weight from the valve train by using a lightweight, high-flowing valve and a set of titanium retainers is also a great idea.