Jim Smart
April 1, 2008

Have you ever had an engine built, only to find yourself unhappy with the result? Our budget FE 390 project was one of those disappointing engine-building experiences. Although it was built by a reputable machine shop, it had a hideous amount of vibration and wasn't performing well--proof that even the best machine shop is only as proficient as its weakest link. All it takes is one person having a bad day to send an engine build into a tailspin.

Because our confidence in the builder was shaken, we decided to visit one we trust--JGM Performance Engineering in Valencia, California. It may surprise you to know JGM Performance Engineering doesn't see very many Ford FE big-blocks. The engine JGM works on most these days is the small-block Ford in low and tall-deck versions in all kinds of displacements.

We're passionate about FE big-blocks and here's why. There remains no replacement for displacement and shear size--that raw, nasty, rotund mass thing that dates back to Roman chariots of yore. Size really does matter and always has. You can have a stump-pulling 427-inch Windsor small-block that makes heaping, helping amounts of torque and horsepower, but does it fill the engine room?

It's always interesting to tear into a fresh rebuild to see what went wrong. We're convinced something was amiss during dynamic balancing, hence the vibration. However, our 390 goes further than that. It's a study in what happens when we have an unhappy combination of parts combined with marginal building technique. Perceived vibration may not have been dynamic balance at all, but rather cylinder-power balance, inconsistent compression, and cylinder pressure between bores. It may also have been improper cam selection and degreeing.

Our 390 FE project demonstrates just how little some builders know. It's easy to hang up a shingle and call yourself an engine builder. We jokingly call them engine "assemblers" because they tend to overlook what's most important in a rebuild. It takes a real engine architect to plan and build an engine properly. For one thing, you can't approach an FE big-block in the same way you would the average small-block. The FE big-block is an old-school, skirted, Y-block design, with all kinds of potential for making big power. However, a street-driven FE should be built for reliability as well as power. To get power for the long haul, you need reliability, and we'll show you how to get it.

Next month, we'll wrap up our Budget FE project with top-end assembly and dyno testing.

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