Join Date: Oct 2001
Location: Brooklyn, Maryland
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Two types of flanges on intakes
There are two types of flanges - spreadbore (Q-jets and similar) and squarebore (Holleys, Carters, and the like). He saying that in order to run the Q-jet, he'd have to run an adapter and he's right, if the intake he has is a Performer RPM or Performer RPM Airgap. The standard Performer is designed to run a spreadbore or squarebore. Usually there's a thin plate that comes with those type of intakes that goes between the carb and intake that gives a squarebore carb a flat surface to press against and create a good seal against the gasket.
That said - I've run a few adapters in the past. I'd highly recommend a four hole adapter, preferable phenolic plastic or wood. The open plenum adapters can mess with the vacuum signal to the carb on a divided plenum intake.
And as far a performance, a squarebore will typically outperform a spreadbore carb, as the primary bores are larger in the squarebore. If you really do some serious modifying to a spreadbore, you can make up for some of that. When I drag raced a mild big block street car, my times were quicker with the squarebore. The BB liked the additional air and fuel.
Here's my take on the cost. Either buy all the bells and whistls for the Holley, or the adapter and use the Q-jet. But the hidden costs are what will also need to be changed and/or modified to hook up the Q-jet. Take into consideration that the choke could be different and the fuel line hookup is different as well. Vacuum lines are very cheap, should longer ones be needed. Also, if the Q-jet needs a rebuild, there's the expense of a kit. To go inside the Holley a fuel bowl gasket set may be needed if the old gasket tears. And in the end... the Holley may be the cheaper fix, but it won't be as great offroad as the Q-jet.
Anyone still awake after all that?