Engine Assembly Basics -- Technical Article -- Engine Masters Magazine

Building The Short-Block

By Steve Dulcich

We know there are many performance enthusiasts who dream about putting together a high performance powerplant, but don't quite have the confidence or experience to jump in. What are some of the tricks, techniques, and tools required to successfully build an engine? With this story we will launch a series of articles aimed at answering just those types of questions. Without a doubt, building a performance engine requires a sound understanding of the fundamentals of assembly, answering the question of "how to do it" as much as "what to do." That's the kind of practical information we are looking to provide.

To really get into the details of how it's done, there's much more content than can possibly be covered in a single story. We've broken down the building process into bite-sized pieces, and will cover an aspect of engine building technique in each following issue. We aren't necessarily aiming at turning our readers into race engine machinists, but hopefully we will provide the background required to assemble a great engine in your own garage. We'll start this month with the short-block, and move on to the cam and valvetrain in the next issue, followed by the top end. We encourage feedback from our readers, so if you have an area of engine building you'd like explained in detail, contact me at steve.dulcich@sorc.com.

Mock Build-up
Before even thinking about breaking out the tools for final engine assembly, step one is to perform a trial or mock-up assembly of some of the major components. The goal here is to identify any problems that will arise in assembly, and take care of them before the real build begins. Usually, the areas to focus on here are clearance issues where non-stock components are being used. Some examples include rod and crank clearance with stroker cranks, lifter and link-bar clearance with roller lifters, or cover clearance when converting to a belt drive. Just about anywhere non-stock parts are being used, take the time to check the fit before final assembly.

Essentially, the mock-up is a test fit of the components, checking for problems as the parts move through their range of motion. It isn't necessary to fully install the parts or torque the fasteners for many of these checks. For instance, for checks like piston deck or rod clearance, the crank can simply be installed with a pair of maincaps and bearings, including the thrust bearing. A piston/pin and rod assembly can be temporarily positioned without the pin locks or rings to verify crankcase clearance, moving the piston from hole to hole. Similarly, a belt drive adapter may just be laid into position, to check for any clearance problems that will hang-up the casting.

The reason for the mock-assembly is that the remedy for most of the problems encountered will usually involve grinding or cutting, so it pays to find these potential problems before things are cleaned up and the engine is partially built. Key items to check in the short-block include rod clearance, rod side clearance, crank counterweight clearance, piston deck height, cam timing, and skirt to counterweight clearance. Top end checks include things like the piston to head clearance, valve to piston clearance, valve lift, retainer to guide clearance, valvetrain geometry, and intake manifold alignment. Several of the checks will involve precision measurements. Many of the precision tools for the job can be had at budget prices from Powerhouse Products or Harbor Freight Tools.