Editor's Note: This is the second of two parts addressing the basics ofengine assembly.
The cylinder heads are where the power is made in an engine. Money spenthere gives a better return of horsepower per dollar than money spentanywhere else in the engine. The selection of cylinder heads is usuallysubject to the rules at the track where you run. Make sure you arespending your dollars on headwork and heads that are legal.
A lot offactors go into selecting the cylinder heads for your engine. Trackrules and your pocketbook are just the beginning. Chevrolet has mademany head castings over the years. A number of them are suitable forracing.
At the least-expensive end might be heads from a 305-cid engine.These heads can have small, 58cc combustion chambers, which give goodcompression with flat-top pistons. These don't flow as well as someothers, but in a class that is not allowed many modifications, thecompression allows them to work quite well. Among the best of these areheads that have a casting number ending in 416 or 601.
The double humpheads have long been a favorite performance part. These arecharacterized by a "double hump" casting mark on each end of the head.There are several casting numbers in this family. Among them are castingnumbers ending in 462, 461, 291, and 186. The 041 casting, while it hasno double hump mark, is about the same as those mentioned above.
Toreally be able to research and identify Chevy cylinder heads, get a copyof Chevy Small-Block Part and Casting Number Guide from Steve SmithAutosports.
The double hump heads are usually expensive. Many have beenraced out and require a lot of work. Some might have modifications notallowed in your class. These heads on a nearly stock engine may not bemuch better than a 305 head. Use these heads when you need to turn 7,000rpm and when you need to make power with a large carb, headers, and abig cam.
With the cost of double hump heads rising, an alternative,where rules allow, is the Chevy Vortec head. This head can be easilyidentified by its center bolt hold-downs on the valve covers. Also, themanifold center bolts are vertical rather than perpendicular to thehead-mating surface. This is a new design that flows well and has goodcompression. I'm told there are a few carbureted manifolds made byChevrolet. I'm also told they are hard to find. An older intake manifoldwill require redrilling of the bolt holes in the heads to install. Thisis not too difficult, but be sure it is allowed under your rules. Vortecheads will be found on many of the later model Chevy V-8-powered carsand pickups.
Cylinder head selection is...
Cylinder head selection is a major source of power. Check your rulebook,as local track rules vary widely. Photos A and B show several types ofcasting marks on the "double hump" heads. These heads are verydesirable for racing. They have been out of production for years.Sometimes they will have been raced out, having cracks or warps.Be wary of buying these unless you can have them checked out.