“What I Learned Today” With Jeff Smith – Don’t Get Small

Editor’s Note: For the next few months, we’ll be sharing weekly lessons that are hard-earned from nearly four decades of garage experiences, exasperations, and general mayhem that either we’ve experienced personally or have been associated with through friends’ miscues. The title intones that most of these errors and screw-ups could have been easily avoided had we been paying attention to the details. So rather than suffer a similar fate, we offer up these lessons learned — the hard way.

Nobody who works on cars ever does it right every time. In fact, some of our best learning moments have come from mistakes or accidents that produced more than one, “Oh, now I understand” moment.

We’ve recreated a few of the best lessons here to help you when you’re working on your hot rod or perhaps Mom’s grocery getter. A few of these may get you out of a jam or perhaps save your wallet from an unnecessary drain. All are intended to help as many as possible get through the continual maze that we put ourselves through in quest of building a better-running street car.

Don’t Get Small

A friend shared this amazing nugget of information. A customer came into a friend’s shop complaining of poor power from his carbureted 540ci big-block Chevy engine in an early Chevelle. His solution was to yank the engine and replace it with a brand new LT4 supercharged crate engine from Chevrolet. Once the LT4 project began, my buddy discovered why the original 540ci Rat motor ran so poorly.

The car was originally built by a different shop and my friend was tasked with the job of making the new EFI engine fit in the Chevelle. During disassembly of the 540’s fuel system, he realized he had not found the fuel filter. Closer examination revealed the original builder had used an extremely small disc-style fuel filter with a filter area roughly the size of a half-dollar coin. When he disassembled the filter, he discovered it was nearly plugged with debris from the fuel tank, allowing only a small amount of fuel to pass through.

This was enough to allow the engine to run at part throttle but the engine would quickly lay down under hard throttle. The filter allowed enough fuel to make the engine run at part throttle but not enough fuel to make sufficient heat at WOT to burn the pistons. The quick and easy solution to the big block’s problem would have been to simply convert to a large, tubular fuel filter with 20 times the filter area. That would have offered enough filter area to trap debris yet not create a flow restriction. Several companies like Aeromotive, Earl’s, Holley, and many others offer multiple filter sizes to fit any application.

The key for a high horsepower engine is to choose the largest filter you can accommodate to allow not only for the dirt and debris to be filtered, but to do so while not restricting the fuel flow capacity. This is why the filter area needs to be large.

What I learned

This is the filter found in that 540ci big-block Chevelle. Imagine trying to feed a hungry 700 hp big-block through a partially clogged fuel filter the size of a large coin.

Several companies like Holley, Aeromotive, Earl’s, and others make different sized fuel filters with removable filter cartridges. Some, like this Holley filter, are stainless steel and can be cleaned and reused.

More Sources

About the author

Jeff Smith

Jeff Smith, a 35-year veteran of automotive journalism, comes to Power Automedia after serving as the senior technical editor at Car Craft magazine. An Iowa native, Smith served a variety of roles at Car Craft before moving to the senior editor role at Hot Rod and Chevy High Performance, and ultimately returning to Car Craft. An accomplished engine builder and technical expert, he will focus on the tech-heavy content that is the foundation of EngineLabs.
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