7 Key Things to Consider When Building a Performance Short-Block
Hot Rod|December 2020
7 Key Things to Consider When Building a Performance Short-Block
Building a performance engine isn’t difficult, and it doesn’t have to be expensive, but it does take knowledge and planning.
John McGann

We spent a couple of days at JMS Racing Engines, in El Monte, California, talking with owner Mike Johnson and his machinists and builders to get the scoop on what makes a successful budget performance-engine build. We’re assuming that you’re starting with an engine that is in good condition and hasn’t had more than one overbore, you plan to reuse as many of the stock components as you can, upgrading to higher-performance pieces as your budget permits, and you do the disassembly and reassembly yourself. As with any complicated process like this there are plenty of myths to bust, and just as many procedures to follow. We’ll break everything down into bite-sized pieces.


JMS Racing Engines; El Monte, CA; 626/579-4567; jmsracing.com

Devise a Plan

We cannot stress this enough—the most important part of any engine build begins with a good plan. By good we mean one that is realistic and fits within your budget. Ask yourself: What do you have to work with, and how much can you afford to spend? Are you starting with a lightly used original bore stock block that just needs new rings, bearings, and a hone, or are you starting with a “mystery motor” of unknown origin? We’ve all heard those stories of free engines that were guaranteed to run but, upon closer inspection, needed a lot of work.

Keep in mind that the cost of the engine is only part of the total build. There is a myriad of other factors to consider: Will your cooling system be able to keep your more powerful engine from overheating? Do you need to reinforce the frame or add a roll bar? Will your transmission, rear end, and axles live behind it? Will you need bigger wheels and tires for better traction? Do you have all the tools you need and space to do the work?

Finally, you’ll come to the age-old question: Am I building a street car or a race car? Decide on this quickly, and the rest of the build will start to fall into place. We’ll guess that most of our readers will have a formula that goes something like this: I have a 3,200-pound car with a C4 and 3.55:1 Traction Lok rear (for example), and I have a stock 5.0 that came out of a ’90 Mustang. I want an engine that will let me drive to the dragstrip and run low 13s, or maybe compete in a few local autocross events. I want it to be able to do burnouts at will, I want to be able to drive it to cruises and car shows without overheating, and I want it to sound good. Oh, and I have $3,000 (again, for example) to spend building the long-block.

Choose a Shop

The next step is to approach a few of your local machine shops to discuss your plan and see what they recommend. Can they work within your budget, and what do you get in the engine they build?

JMS’ Mike Johnson says it’s important to find a machine shop you can trust. Look at the shop. Are things clean and orderly, especially in the assembly area? How long have they been in business? What do their customers have to say about them? How willing are they to spend the time with you discussing your options and answering your questions? If you’re met with rudeness or impatience, don’t waste your time with that particular shop. Go find another. By the same token, don’t be a pain in the ass. Tell them what you have and what you want and listen to their recommendations. It’s OK to discuss why they recommend a certain procedure or brand of parts, but it’s probably not a good idea to tell them how to do their jobs.


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December 2020