Ethanol Fuel and Vintage Vehicles - Ethanol Education

Conceding that ethanol-blend fuel is a mainstay, most modern fuel-system components produced by OEM-types, such as rubber-hose and stock-replacement fuel pumps, are compatible with it. Major aftermarket fuel-system companies like Holley and Barry Grant made the switch to ethanol-friendly gaskets and rubber components several years ago, too. And many restoration suppliers offer pre-bent stainless steel fuel lines that are impervious to ethanol, while maintaining a stock look for myriad applications, if corrosion is a concern.

With so many replacement options that effectively eliminate failure on the market, what about the Rochester Quadrajet? It remains a popular hobbyist choice, but hasn't been in production for years. There are a countless number of them in service today, yet it's unlikely that most are prepared to ward off the effects of ethanol-blend fuel. So what are its susceptible components, and what can be used as a replacement? Here's one expert's opinion on the matter.

Preparing Your Pontiac For EthanolCliff Ruggles is intimately familiar with Rochester Quadrajets. His company, Cliff's High Performance in Mount Vernon, Ohio, prepares hundreds of them each year for its customers' factory-restored and/or performance-modified applications. When asked about the negative attributes associated with ethanol-blend fuel, Ruggles replies, "Current fuel is fine for high-performance use. Our large-cube Pontiac engine produces more than 575 hp with it, but even at a blend of 10 percent, ethanol can be extremely hard on certain components within the carburetor."

The actual castings, gaskets, and metering jets and rods are largely unaffected by ethanol, but the accelerator pump cup is one piece that's extremely susceptible to failure when exposed to it. "Low-quality black rubber cups tend to swell almost immediately," says Cliff. "The rubber first gets soft and sticky and then becomes hard and brittle when it dries. Modern dark-blue cups made of high-grade fluorelastomers are specifically designed for use with oxygenated fuels, and are the only ones that we recommend."

The original rubber-tipped valve of the needle-and-seat assembly is another component that's not totally compatible with ethanol-blend fuel. "The tips get soft and sticky and erode horribly," he adds. "Nearly all modern units feature a Viton tip, which is unaffected by ethanol, so there's far less of a concern. It's pretty easy to differentiate an original rubber-tipped needle valve from a Viton-tipped replacement: The rubber is dull, while Viton has a sheen."

The Quadrajet rebuild kits available from Cliff's High Performance are entirely compatible with ethanol-blend fuel. "We carefully assemble ours using proven components that won't fail over time. Our long-term testing is a continual process. We've had certain rubber components and nitrofyl floats submerged in ethanol-blend fuel for a year or longer. We use only those components that we're completely confident with."

Knowing that ethanol generates less energy per volume than gasoline, we asked Ruggles if carburetors must be recalibrated for use with ethanol-blend fuel. "At a blend of 10 percent (E10), there's really no a need to adjust the carburetor's fuel metering curve simply to accommodate its use. The Quadrajet is a very efficient piece that does an excellent job of atomizing fuel molecules for maximum performance, so the engine will tell you what it wants.

He continues, "We have to consider that very few Pontiac engines are completely original and maintain a fully-functional emissions system. Even the smallest change outside the stock setting requires that its Quadrajet be slightly recalibrated to maintain peak performance. This includes spark timing or vacuum advance adjustments, a thermostat with a different temperature rating, the addition of an aftermarket intake manifold, or blocking an exhaust crossover."