Holley question

[VintageMusclecar]

Keith;

Sometimes the spreadbore Holleys run fairly well depending on the application...they key words being "sometimes" and "depending on the application."

The reason I'm not a big fan of them is because compared to a Quadrajet, they're barely more than a controlled fuel leak in regards to metering precision. The primary metering system on a QJet is a fantastic design, and incredibly precise under nearly every imagineable driving situation. The Holley metering system is "primitave" at best in comparison to a QJet in this regards, which is why I recommend a QJet over a Holley if someone is set on using a spreadbore design carburetor.

OTOH, while it is possible to tune a QJet to deliver big power #'s and low e.t's at the digs, the QJet does have some inherent "issues" (i.e. flaws) in comparison to a Holley <u>when pressed to the extremes</u>. A QJet only has one needle&amp;seat assembly, making it difficult to provide adequate fuel flow into the carb. (it is obviously possible, but it's done using a huge nedle&amp;seat that doesn't lend itself to street use because of fuel control issues). A Qjet also has a limited fuel storage capacity inside the main body, which can require some modifications to provide an adequate fuel supply under extreme conditions.

Lastly, no matter how you slice it, a spreadbore design will nearly always have some distribution issues because of the small (relatively speaking) primaries and manhole cover-sized secondarys.

Again, both QJets and Holleys have their places, and can both be made to work in a variety of situations, but when it comes to running a spreadbore, the QJet has the Holley beat hands-down.

Eric